title: Petr Čech

text: Despite him being second choice, Mourinho stated that Čech would not be sold in the January 2015 transfer window due to third-choice Mark Schwarzer leaving for Leicester City. During that month, Čech made back to back starts in the Premier League against Newcastle United at home, followed by Swansea City away from home, keeping clean sheets in both wins. On 1 March 2015, Čech started in goal in the 2015 League Cup final against Tottenham Hotspur, keeping a clean sheet in a 2–0 victory to win the trophy for the third time in his career.


title: Petr Čech

text: Čech signed for Chelsea's Premier League rivals Arsenal on a four-year contract on 29 June 2015, for a fee of around £10 million. His move saw him subjected to death threats by a few Chelsea supporters. The departure of Wojciech Szczęsny to Roma on loan made Čech first-choice goalkeeper ahead of David Ospina. On 2 August, Čech won his first trophy with Arsenal after beating former side Chelsea 1–0 in the 2015 FA Community Shield. A week later, he made his Premier League debut for Arsenal in a 2–0 home defeat to West Ham. On 20 October, he made his first Champions League appearance for Arsenal in a 2–0 win against Bayern Munich.


title: Petr Čech

text: Čech recorded his 170th Premier League clean sheet in a 2–0 win against AFC Bournemouth on 28 December 2015, setting a new league record and overtaking previous record holder David James. On 2 March 2016, he was sidelined due to a calf injury while playing against Swansea. On 2 April, he returned as an unused substitute against Watford and returned to the pitch on 17 April against Crystal Palace in a narrow 1–1 draw and guided Arsenal to its 500th Premier League win on 21 April against West Brom. Marking the end of his debut season with Arsenal, he was named the Premier League Goalkeeper of the season by critics and platforms for winning the Golden Glove with an under-performing defence.


title: Petr Čech

text: Čech was given the captain's armband for Arsenal in their 4–3 opening day home loss to Liverpool. In September 2016, he featured for the full 90 minutes in a 3–0 rout by Arsenal of his former side Chelsea at the Emirates. On 24 April 2017, Čech played in the 2016–17 FA Cup semi-final against Manchester City at Wembley, which Arsenal won 2–1. During this season, Cech received mild criticism among Arsenal fans for his inability to play with the ball at his feet but meanwhile he had the third most clearances among all goalkeepers in Premier League with 11 which manifested his transformation into a "sweeper keeper". Čech again held the captain's armband on 10 May 2017 in a 2–0 win over Southampton at the St Mary's Stadium. Čech was sidelined for the FA Cup Final due to injury, but Arsenal beat Chelsea 2–1. Čech won his fifth FA Cup, and Arsenal became the most successful club in the history of the competition with 13 tournament wins.


title: Petr Čech

text: Čech was Arsenal's starting goalkeeper in the 2017 Community Shield, against his former club Chelsea; following a 1–1 draw after regulation time, Arsenal won the match in a 4–1 penalty shoot-out, in which neither keeper saved a spot kick.


title: Petr Čech

text: On 11 March 2018, Čech became the first Premier League goalkeeper to keep 200 league clean sheets, after a match against Watford in which he saved a penalty from Troy Deeney.


title: Petr Čech

text: Čech started the season as the first choice in goal for new manager Unai Emery, but later lost his place to new signing Bernd Leno after suffering a hamstring injury during a match against Watford. On 15 January 2019, Čech announced via open letter on Twitter that he would retire at the end of the season. On 29 May, he made the final appearance of his career in Arsenal's 4–1 defeat to his former club Chelsea in the 2019 UEFA Europa League Final. Several media outlets described him as Arsenal's Man of the Match.


title: Petr Čech

text: Čech first represented his country in November 1997 with the under-15 team, working his way up through different age groups before making his senior debut for the Czech Republic in February 2002. He first came to prominence as a 20-year-old at the 2002 U-21 European Championships when his penalty shoot-out heroics in the final against France, letting in only one of the penalty kicks, earned the Czech Republic their first title at youth level.


title: Petr Čech

text: After establishing himself as the senior team's first choice goalkeeper, Čech was selected in the Czech Republic's squad for UEFA Euro 2004. Čech's saves helped his team progress to the semi-finals, where they lost to eventual winners Greece on the silver goal rule. He was named in the all-star team as best goalkeeper at the tournament.


title: Petr Čech

text: The Czech Republic qualified for the 2006 World Cup, held in Germany, and were placed in Group E, alongside Ghana, Italy and the United States. The Czech Republic finished third in their group, following a 3–0 win against the United States, and two losses against Ghana and Italy, the score 2–0 in both games, thus not qualifying for the knock-out stages of the tournament.


title: Petr Čech

text: On 17 October 2007, Čech captained the Czech Republic team in their Euro 2008 Group D qualifier against Germany. He kept a clean sheet and the Czechs defeated Germany 3–0 away to book their place for the finals in Austria and Switzerland. In the last group game of the final tournament, Čech was beaten three times in the final 15 minutes as Turkey overcame a two-goal deficit to knock the Czechs out. Čech had a cross slip through his hands, allowing Nihat Kahveci to score Turkey's equalising goal.


title: Petr Čech

text: On 29 May 2012, Čech was named in the Czech Republic's squad for Euro 2012 in Poland and Ukraine. In the Czech Republic's group match against Greece, a fumble from Čech allowed the Greeks a goal. The match, however, finished 2–1 in the Czech Republic's favour. Čech deputised for the injured Tomáš Rosický as captain in the final group match against Poland, as the Czech Republic qualified for the quarter-final with a 1–0 win. Čech's captaincy continued in the quarter-final, where the Czechs lost to Portugal through a 79th-minute Cristiano Ronaldo goal.


title: Petr Čech

text: On 26 March 2013, Čech made his 100th appearance for the Czech Republic, keeping a clean sheet in a 3–0 win over Armenia. He equalled the national record of former teammate Karel Poborský on 17 November 2015, when he earned his 118th cap in a 3–1 loss to neighbours Poland in Wrocław. The following 27 May, he took the record outright by playing in a 6–0 friendly win over Malta.


title: Petr Čech

text: On 8 July 2016, Čech announced his retirement from international football. He is the most capped player in the history of the Czech team, with 124 caps.


title: Petr Čech

text: In October 2020, Čech was included in Chelsea's 25-man Premier League squad for the 2020–21 season. The club announced that Čech was included as an emergency goalkeeper and as a non-contract player, and that this was a precautionary move due to the COVID-19 pandemic. He made one appearance for the Chelsea's under-23 team in the Premier League 2.


title: Petr Čech

text: During a protest against the proposed European Super League outside Stamford Bridge on 20 April 2021, Čech approached fans who were blocking the team bus and could be heard saying "give us time". The fans did move and the team bus was able to enter after a short delay. Later that day, Chelsea were among the first clubs to withdraw from the league.


title: Petr Čech

text: On 9 October 2019, Čech signed for ice hockey side Guildford Phoenix of the National Ice Hockey League Division 2 (level 4 of British hockey) as a goaltender. He chose to wear number 39 jersey in honour of Dominik Hašek. Čech said he would continue his role as a technical and performance advisor at Chelsea whilst playing ice hockey in his spare time. He was named the man of the match on his ice hockey debut on 13 October, after stopping two penalties in a shoot-out victory, and making several other crucial saves. After winning a treble with Guildford Phoenix in the 2021–22 season, Čech signed for the National Ice Hockey League Division 1 side Chelmsford Chieftains in November 2022.


title: Petr Čech

text: Since his emergence as a precocious talent in his youth, Čech has been considered to be one of the greatest, most consistent, and most respected goalkeepers both of his generation and of all time. A tall, athletic, agile, brave, physically strong, and well-rounded keeper, with a strong mentality, as well as good decision-making and leadership qualities; throughout his career he has stood out for his reflexes and shot-stopping abilities, as well as his positional sense, concentration, defence organisation, handling when coming off his line to claim crosses, and command of his area.


title: Petr Čech

text: Although Čech is not as adept with the ball at his feet as the newer generation of goalkeepers that emerged in his later career, he possesses a deep kick with either foot, despite being naturally left-footed. His ability to produce deep kicks and long throws came to use in his Chelsea days for starting quick counter-attacks which were an important part of their game. In his later career, he often functioned as a sweeper keeper, due to his ability to rush off his line, anticipate opponents who had beaten the offside trap, and clear the ball away from danger. Čech is also known for his penalty-saving abilities. Some examples of his penalty saves in high-profile matches include those made in the 2012 UEFA Champions League Final, the 2010 FA Cup Final, and his penalty save against Blackburn during the 2004–05 season, which helped him beat Peter Schmeichel's Premier League record of 694 minutes without conceding a goal.


title: Petr Čech

text: Čech is considered to be one of the greatest goalkeepers both of his generation and of all time, as well as one of the best keepers in Premier League history, and has earned praise from several players, pundits, and managers due to his goalkeeping ability. Fellow goalkeeper Gianluigi Buffon named Čech as the best goalkeeper of his era, saying: "The best goalkeeper with his feet? Pepe Reina. In the air I'd say Neuer. With his hands: Casillas. The best overall I'd say is Čech." Iker Casillas instead described him as, "One of the best goalkeepers I have ever seen" via his Twitter account. Former Arsenal manager Arsène Wenger and goalkeeper Jens Lehmann have hailed him as "one of the greatest of all time". Journalist Alan Tyers of "The Telegraph" described Čech as the "Premier League's best-ever goalkeeper" in 2019.


title: Petr Čech

text: Čech currently holds two Guinness World Records for the most clean sheets in English Premier League history, and for winning the Premier League Golden Glove Award with two different clubs. Nathan Baxter, Martin Dúbravka, Marek Rodák and João Virgínia are some of the goalkeepers who have described him as their idol. In 2011, Čech was voted the third best goalkeeper of the first decade of 21st century by IFFHS. He also has the third highest number of clean sheets (391) since 2000s among all goalkeepers. Former Premier League striker and record-goalscorer Alan Shearer named Čech in his Premier League's "Team of the Decade" in 2019.


title: Petr Čech

text: Čech was born a triplet along with his sister Šárka and a brother named Michal in Plzeň, Czechoslovakia. He has a weaker skull as a result of being a triplet.


title: Petr Čech

text: Čech married Martina Dolejšová (now Čechová) (b. 1982), also of Czech nationality, in June 2003. They have a daughter Adéla (b. 23 January 2008) and a son Damián (b. June 2009),


title: Petr Čech

text: He is a keen musician and plays the drums. He has a YouTube channel under his own name on which he posts video drum covers, including Incubus' "Anna Molly", as well as songs by Coldplay and Foo Fighters. He has played with Roger Taylor of Queen. In May 2019, he and Taylor released a charity single called "That's Football." In 2020, he joined folk rock band Wills & The Willing as their drummer, filming their music video "Iceberg".


title: Petr Čech

text: Along with his native language Czech, Čech also speaks English, French, German, Italian, Portuguese and Spanish.


title: W.A.S.P. (band)

text: W.A.S.P. is an American heavy metal band formed in 1982. They emerged from the early 1980s Los Angeles heavy metal scene. The band's popularity peaked that decade, yet they continue to record and tour, making them one of the most enduring of the West Coast heavy metal bands. W.A.S.P. gained notoriety for their shock rock-themed image, lyrics and live performances. They are estimated to have sold over twelve million records worldwide, with their first two albums, "W.A.S.P." (1984) and "The Last Command" (1985), being certified as gold by the RIAA.


title: W.A.S.P. (band)

text: W.A.S.P. was a prominent target in the mid-1980s of the Parents Music Resource Center (PMRC), an organization that pushed for warning labels on recorded music. The band immortalized its fight with the PMRC on the song "Harder, Faster" from their 1987 live album, "Live...In the Raw". Their most well-known songs include "Animal (Fuck Like a Beast)", "I Wanna Be Somebody", "L.O.V.E. Machine", "Wild Child", "Blind in Texas", "Forever Free", "Mean Man", "Chainsaw Charlie (Murders in the New Morgue)" and "The Idol", as well as their cover versions of Ray Charles' "I Don't Need No Doctor" and The Who's "The Real Me". The band's most recent album, "Golgotha", was released in 2015 and they have reportedly been working on new material.


title: W.A.S.P. (band)

text: W.A.S.P. began following the demise of Circus Circus, a Los Angeles-based band featuring Blackie Lawless and Randy Piper. The original lineup of W.A.S.P. was formed in Los Angeles, California, in 1982 by Lawless, Piper, Rik Fox, and Tony Richards. The band became notorious for its raunchy and, at times, shocking live shows. Lawless was known to tie semi-naked models to a torture rack, and to also hurl raw meat into the audience. The band's debut single, entitled "Animal (Fuck Like A Beast)", and its cover were equally controversial.


title: W.A.S.P. (band)

text: The first lineup did not last for long, as Rik Fox was let go and went on to join the band Steeler with vocalist Ron Keel and guitarist Yngwie Malmsteen. He was replaced by Don Costa, the bassist in Richards' former band, Dante Fox (which later evolved into Great White). Shortly afterward, Costa also left the band and his position on the bass was filled by Brayden Parker. At the same time, guitarist Chris Holmes joined the band.


title: W.A.S.P. (band)

text: W.A.S.P. signed to Capitol Records for their debut album, "W.A.S.P.", released on August 17, 1984. The debut was at one time planned for release with the title "Winged Assassins". The band's first single "Animal (Fuck Like a Beast)" was omitted from the album in the United States to prevent it from being banned from major chain stores. "W.A.S.P." was accompanied by the band's first world tour, performing with numerous bands such as Kiss, Iron Maiden, Metallica, Dokken, Krokus, Helix, Quiet Riot, and Armored Saint.


title: W.A.S.P. (band)

text: Shortly afterwards, the band made an appearance in the 1984 film "The Dungeonmaster" and on the soundtrack to "Ghost Warrior" with the song "Tormentor".


title: W.A.S.P. (band)

text: "L.O.V.E. Machine" and "I Wanna Be Somebody" helped the album sell, and set the band up for "Blind In Texas", a song written in St. Paul, Minnesota, by Lawless. The song was released on their next album "The Last Command" in September 1985. "The Last Command" remains W.A.S.P.'s highest-charting album, peaking at No. 47 on the Billboard album chart. "Blind in Texas" is perhaps their best known song, more than three decades after its release. "The Last Command" was also the first album with new drummer Steve Riley (formerly of Keel), who had replaced Richards at the beginning of the 1984-1985 tour. W.A.S.P. supported the album by participating in two arena tours, first opening for Kiss on their "Asylum" tour, and then, along with Anthrax, they supported Black Sabbath on their "Seventh Star" tour.


title: W.A.S.P. (band)

text: After "The Last Command" tour, Piper departed the band. Former King Kobra bassist Johnny Rod joined W.A.S.P. as Lawless went back to playing rhythm guitar. Around this time, W.A.S.P. became a very prominent target of the Parents Music Resource Center (PMRC), an organization led by Tipper Gore and dedicated to opposing music with lyrics deemed violent or overtly sexual in content. This lowered the band's reputation to such a degree that concert halls were getting bomb threats, band members were receiving death threats by the hundreds, and Lawless was shot at twice (though not hit). The controversy generated valuable publicity for the band.


title: W.A.S.P. (band)

text: With the lineup changes made, they recorded their third album, titled "Inside the Electric Circus". It was released in October 1986, and a near year-long world tour in support of the album followed, including supporting Iron Maiden on their "Somewhere in Time" tour in Europe, and a headlining North American tour with Slayer, Raven and Saxon. "Inside the Electric Circus" received a mixed reaction from the music press: it was considered a big hit with W.A.S.P. fans, while critics, on the other hand, dismissed it as "7th-grader rock". Songs like "Shoot From The Hip" and the minor hit single "95-N.A.S.T.Y." helped the band live up to the reputation of one of the possible meanings of their band name, "We Are Sexual Perverts". However, Blackie Lawless himself, known to be a harsh critic of his own work, cited in the album's re-release liner notes that "Inside the Electric Circus" was "[a] tired record by a tired band." Ultimately it was an unfavorable critical review of the single "95-N.A.S.T.Y." that convinced Lawless to take some time off and reconsider the band's creative direction.


title: W.A.S.P. (band)

text: In 1987, W.A.S.P. had their song "Scream Until You Like It" included on the soundtrack of the movie "Ghoulies 2". The same year, a few dates during the "Inside the Electric Circus" tour were recorded and on November 27, 1987, the Long Beach arena concert was released as the "Live...In the Raw" album. By this time, Riley had left W.A.S.P. to join L.A. Guns, and was replaced by local drummer Chad Nelson. Eighteen-year-old Glenn Soderling, who had recorded an album in 1983 with the band Pandemonium, then joined the band, but did not play any shows due to Holmes' illness. Soderling left during rehearsals and was replaced by Kelly Martella for their Donington appearance and a "Top of the Pops" performance of "Scream Until You Like It" on BBC. Martella went on to join the band Silent Rage (Simmons Records) in 1988. Soderling later surfaced under the name "Tripp Holland" in the band Engines of Aggression with former Tomorrow's Child members Rik Schaffer and Craig Dollinger, and is currently making music for TV shows as staff writer with Supersonic Noise.


title: W.A.S.P. (band)

text: W.A.S.P.'s fourth studio album, "The Headless Children", was released on April 15, 1989, and was their first album without any overtly sexually explicit songs. The album reached the band's highest chart position with No. 48 on the "Billboard" 200 before falling off the charts in 13 weeks. However, it was W.A.S.P.'s most critically acclaimed work up to that point and, according to a recent Lawless interview, it is now the highest-selling W.A.S.P. album to date. The drumming duties for the album were handled by former Quiet Riot drummer Frankie Banali. It features two of the band's most highly acclaimed songs, the power ballad "Forever Free" and a cover of The Who's "The Real Me". W.A.S.P. went on tour in the United States with Accept and Metal Church to support "The Headless Children", playing at smaller venues such as clubs and theaters, as opposed to the arenas and stadiums that had propelled the band into success.


title: W.A.S.P. (band)

text: Chris Holmes left the band in August 1989, stating that he wanted to "have fun, you know." Lawless responded with a caustic remark about the fact that "some guys want to stay at home and wear aprons," hinting at the nature of Chris Holmes' relationship with his new wife Lita Ford. The band effectively disbanded a few months later, with Blackie Lawless embarking on a short lived solo career. Lawless was originally slated to play the T-1000 terminator in the movie "", but was later replaced by Robert Patrick after Arnold Schwarzenegger deemed Lawless "too tall" (1.93m). Blackie commenced work on his solo project, but under pressure from both promoters and fans, he released it as a W.A.S.P. album. Ironically, many critics feel that the resulting concept album, "The Crimson Idol", has been the best W.A.S.P. output so far.


title: W.A.S.P. (band)

text: The follow-up to "The Crimson Idol" was "Still Not Black Enough" (1995), a collection of dark, introspective tunes that extended the "Crimson Idol" mythology. This time, rather than "hiding behind" alter ego Jonathan Steele, Lawless spoke directly to the audience about his own feelings (as stated in the liner notes). While the album lacked the cohesiveness of its predecessor, the lyrics still explored similar topics to "Crimson Idol": being an outcast and misfit, the pressures of fame and society, and the search for love. "Still Not Black Enough" also included cover songs as "bonus tracks". The initial European edition included a different track listing from the American version and a subsequent American re-issue featured yet a different track listing. No version to date includes all the various tracks on one disc.


title: W.A.S.P. (band)

text: Chris Holmes returned to W.A.S.P. in 1996 and together they released "Kill.Fuck.Die" (1997) and "Helldorado" (1999). They also recorded two live albums from these tours, "Double Live Assassins" and "" respectively. "The Sting" CD and DVD were taken directly from an experimental webcast that Lawless claims to have had no control over. This release angered him as he was unhappy with the sound and picture quality.


title: W.A.S.P. (band)

text: The band continued with the album "Unholy Terror" in 2001. Chris Holmes left the band once again in 2001, stating that he wanted to "play the blues". He hooked up with fellow ex-W.A.S.P. member Randy Piper's band Animal, but soon dropped out of that project also. Holmes, for his part, has claimed he never played on "Unholy Terror".


title: W.A.S.P. (band)

text: "Dying for the World", released in 2002, was written and recorded in less than a year which is very fast by Lawless' perfectionist standards. Its liner notes feature one of Lawless' strongest statements about political correctness, inspired by the 9/11 terrorist attacks.


title: W.A.S.P. (band)

text: In April 2004, W.A.S.P. released the first part of "The Neon God", subtitled "", a conceptual album about an abused and orphaned boy who finds that he has the ability to read and manipulate people. The second part, "", was released in September 2004.


title: W.A.S.P. (band)

text: In 2005, W.A.S.P. headlined American Metal Blast. A video shoot for the track "Never Say Die" was planned with Ward Boult, a fetish photographer, directing. To this day, there has been no news as to whether the shoot resulted in anything concrete. It would have been the first W.A.S.P. promo video in ten years, the last being 1995's "Black Forever".


title: W.A.S.P. (band)

text: Early 2006 saw the seemingly stable lineup fall apart. Long-time session and tour drummer Stet Howland left first (on amicable terms), promising more specific information about the reasons for the split to be posted on his website. Larry Howe of Vicious Rumors was considered as a replacement. In May, the departure of guitarist Darrell Roberts, who went on to join the band Five Finger Death Punch, was announced and new guitar player Mark Zavon was brought in several days before the first tour date. The same press release confirmed Mike Dupke, and not Howe, would be the new drummer. Furthermore, two days later, Zavon was out of the picture as well, seeing Doug Blair step in on guitar.


title: W.A.S.P. (band)

text: A new album, "Dominator" was planned for release in October 2006, according to a statement made by Blackie Lawless at a tour stop in Kavarna. He then went on to play a new song from the album, entitled "Mercy". A few weeks later, the release of the album was postponed until April 2007, with the band recording two news songs and dropping two cover songs, to be used instead as bonus tracks. In October 2007, W.A.S.P. embarked on The Crimson Idol Tour, to celebrate that album's 15th anniversary. It was the first time that the album, often regarded to be among the band's finest work, was performed in full from start to finish. The tour kicked off in Greece, in Thessaloniki at the Principal Club Theater on October 26, 2007.


title: W.A.S.P. (band)

text: The release of the "Dominator" album was finalized for April 16 in the UK, April 20 in Scandinavia with the rest of mainland Europe following on April 27. The release dates for South America and Russia followed in early May.


title: W.A.S.P. (band)

text: W.A.S.P. canceled their North American tour due to their record label's loss of a distributor. They were going to finish up their shows in Europe and then reschedule their shows in the United States. They were unable to finish the shows in Europe because of a "family illness that needed immediate attention" which forced the band to return to Los Angeles right away. They were originally going to perform at Rocklahoma. As the tour was canceled, W.A.S.P. was not able to perform at Rocklahoma and was replaced by Queensrÿche.


title: W.A.S.P. (band)

text: W.A.S.P. announced a European tour which included dates in Scotland, England and other places throughout Europe in late October 2007.


title: W.A.S.P. (band)

text: W.A.S.P. released their fourteenth studio album, entitled "Babylon" in late 2009, via Demolition Records.


title: W.A.S.P. (band)

text: Shortly after the release of "Babylon", Blackie Lawless declared that he was never going to play the song "Animal (Fuck Like A Beast)" live again, due to his religious beliefs. These beliefs are what have allegedly been behind Blackie Lawless' self-censorship of his own lyrics during the "Babylon World Tour", most notably during the performance of "Chainsaw Charlie (Murders In The New Morgue)".


title: W.A.S.P. (band)

text: On The Beast of Babylon Tour, Blackie canceled two shows within a week of each other. The first cancellation came about at the Gramercy Theater in New York City after the band discovered that the venue had been selling V.I.P. meet and greet tickets for twice the amount of the general admission price. The band made a statement claiming, "We have never charged a fan for an autograph and will never charge any fans for an autograph." The second cancellation occurred when the Crocodile Rock venue in Allentown, Pennsylvania wanted 50% of all of the band's profit, according to Lawless.


title: W.A.S.P. (band)

text: On September 21, 2012, the band celebrated the 30th anniversary of their first ever live show by kicking off a world tour at The Forum in London. The set for the tour was split into three sections: songs from the first four albums, a cut-down rendition of the Crimson Idol performance and a final segment for newer material.


title: W.A.S.P. (band)

text: W.A.S.P.'s fifteenth studio album, "Golgotha", was released on October 2, 2015. The album took four years to materialize.


title: W.A.S.P. (band)

text: W.A.S.P. toured in 2017 to commemorate the 25th anniversary of the release of "The Crimson Idol". To coincide with this anniversary, the band released "" on February 2, 2018, which came with the original "The Crimson Idol" movie on DVD and Blu-ray, and includes six tracks that were originally intended to be part of the original version of the album.


title: W.A.S.P. (band)

text: In December 2017, it was reported that W.A.S.P. had been working on new material for the follow-up to "Golgotha". No news on the album had surfaced for more than three years, until December 2020 when "Loudwire" listed it as one of the 88 "Most Anticipated Rock + Metal Albums" of 2021. Progress on a new album had continued to be slow by January 2022, when frontman Blackie Lawless stated in an interview with Eddie Trunk that the band has "quite a bit of material that [they've] been working on diligently actually."


title: W.A.S.P. (band)

text: Former W.A.S.P. drummer Frankie Banali died of pancreatic cancer on August 20, 2020, making him the second deceased member of "The Crimson Idol"-era lineup, following Bob Kulick who had died three months earlier.


title: W.A.S.P. (band)

text: In late October 2021, it was announced that W.A.S.P. would embark on a world tour in 2022, celebrating the 40th anniversary of the band. The European tour, however, was postponed and rescheduled to spring 2023 due to the ongoing pandemic situation in Europe, including the shows in Russia in May. But keeping their first North American tour in over a decade from October to December, with support from Armored Saint, and on selected dates, Michael Schenker.


title: W.A.S.P. (band)

text: There has been much speculation over the origin of the band's name, and whether it actually stands for anything, since it is written as an acronym. One possible interpretation is "White Anglo-Saxon Protestants", being the original meaning of the acronym. The song "Show No Mercy", the B-side of the band's first single "Animal", contains the repeated lyric, "White Anglo-Saxon / A violent reaction".


title: W.A.S.P. (band)

text: The original U.S. release of the band's debut album "W.A.S.P." had the words "We Are Sexual Perverts" inscribed on both sides around the label in the center, while "Winged Assassins" is inscribed on the spine of the first vinyl pressing. When asked about the band's name, Lawless has avoided giving a straight answer. In one interview he answered, "We Ain't Sure, Pal."


title: W.A.S.P. (band)

text: In a February 2010 interview, Lawless stated the main reason for the name was the periods. He claimed no band had ever used them before (although R.E.M. formed two years earlier) and, in essence, the periods created a "question mark of uncertainty" to make W.A.S.P. stand out more. He then went on to say, "Look where we are: it did!"


title: W.A.S.P. (band)

text: In an interview published on YouTube in 2020, former bassist Rik Fox explained that the name came about after an incident outside Lawless' home, in which Fox happened across a hornet and tried to kill it before it could sting him. The sight of the insect's throbbing stinger brought to mind the image of the Green Hornet logo. According to Fox, this happened while the band was still under the moniker of "Sister" and Lawless was looking for a new name. When Fox explained what happened to Lawless, the band's leader liked the idea and ultimately adopted it. Fox's story has been corroborated by former guitarist Randy Piper, who while agreeing with him, did acknowledge Lawless as being the one who came up with the idea of the band's name being written as an acronym.


title: Command-line interface

text: A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and providing information to them as to what actions they are to perform. In some cases the invocation is conditional based on conditions established by the user or previous executables. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods.


title: Command-line interface

text: Today, many users rely upon graphical user interfaces and menu-driven interactions. However, some programming and maintenance tasks may not have a graphical user interface and use a command line.


title: Command-line interface

text: Alternatives to the command-line interface include text-based user interface menus (for example, IBM AIX SMIT), keyboard shortcuts, and various desktop metaphors centered on the pointer (usually controlled with a mouse). Examples of this include the Microsoft Windows, DOS Shell, and Mouse Systems PowerPanel. Command-line interfaces are often implemented in terminal devices that are also capable of screen-oriented text-based user interfaces that use cursor addressing to place symbols on a display screen.


title: Command-line interface

text: Many software systems implement command-line interfaces for control and operation. This includes programming environments and utility programs.


title: Command-line interface

text: Compared with a graphical user interface, a command-line interface requires fewer system resources to implement. Since options to commands are given in a few characters in each command line, an experienced user often finds the options easier to access. Automation of repetitive tasks is simplified by line editing and history mechanisms for storing frequently used sequences; this may extend to a scripting language that can take parameters and variable options. A command-line history can be kept, allowing review or repetition of commands.


title: Command-line interface

text: A command-line system may require paper or online manuals for the user's reference, although often a "help" option provides a concise review of the options of a command. The command-line environment may not provide graphical enhancements such as different fonts or extended edit windows found in a GUI. It may be difficult for a new user to become familiar with all the commands and options available, compared with the icons and drop-down menus of a graphical user interface, without reference to manuals.


title: Command-line interface

text: Operating system (OS) command-line interfaces are usually distinct programs supplied with the operating system. A program that implements such a text interface is often called a command-line interpreter, command processor or shell.


title: Command-line interface

text: Examples of command-line interpreters include DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11, the various Unix shells (sh, ksh, csh, tcsh, zsh, Bash, etc.), CP/M's CCP, DOS' COMMAND.COM, as well as the OS/2 and the Windows CMD.EXE programs, the latter groups being based heavily on DEC's RSX-11 and RSTS CLIs. Under most operating systems, it is possible to replace the default shell program with alternatives; examples include 4DOS for DOS, 4OS2 for OS/2, and 4NT / Take Command for Windows.


title: Command-line interface

text: Although the term 'shell' is often used to describe a command-line interpreter, strictly speaking, a 'shell' can be any program that constitutes the user-interface, including fully graphically oriented ones. For example, the default Windows GUI is a shell program named EXPLORER.EXE, as defined in the SHELL=EXPLORER.EXE line in the WIN.INI configuration file. These programs are shells, but not CLIs.


title: Command-line interface

text: An application program may support none, any, or all of these three major types of command-line interface mechanisms:


title: Command-line interface

text: Some applications support a CLI, presenting their own prompt to the user and accepting command lines. Other programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file. In other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality. For example, all features of MATLAB, a numerical analysis computer program, are available via the CLI, whereas the MATLAB GUI exposes only a subset of features.


title: Command-line interface

text: In Colossal Cave Adventure from 1975, the user uses a CLI to enter one or two words to explore a cave system.


title: Command-line interface

text: The command-line interface evolved from a form of communication conducted by people over teleprinter (TTY) machines. Sometimes these involved sending an order or a confirmation using telex. Early computer systems often used teleprinter as the means of interaction with an operator.


title: Command-line interface

text: The mechanical teleprinter was replaced by a "glass tty", a keyboard and screen emulating the teleprinter. "Smart" terminals permitted additional functions, such as cursor movement over the entire screen, or local editing of data on the terminal for transmission to the computer. As the microcomputer revolution replaced the traditionalminicomputer + terminalstime sharing architecture, hardware terminals were replaced by terminal emulators — PC software that interpreted terminal signals sent through the PC's serial ports. These were typically used to interface an organization's new PC's with their existing mini- or mainframe computers, or to connect PC to PC. Some of these PCs were running Bulletin Board System software.


title: Command-line interface

text: Early operating system CLIs were implemented as part of resident monitor programs, and could not easily be replaced. The first implementation of the shell as a replaceable component was part of the Multics time-sharing operating system. In 1964, MIT Computation Center staff member Louis Pouzin developed the RUNCOM tool for executing command scripts while allowing argument substitution. Pouzin coined the term "shell" to describe the technique of using commands like a programming language, and wrote a paper about how to implement the idea in the Multics operating system. Pouzin returned to his native France in 1965, and the first Multics shell was developed by Glenda Schroeder.


title: Command-line interface

text: The first Unix shell, the V6 shell, was developed by Ken Thompson in 1971 at Bell Labs and was modeled after Schroeder's Multics shell. The Bourne shell was introduced in 1977 as a replacement for the V6 shell. Although it is used as an interactive command interpreter, it was also intended as a scripting language and contains most of the features that are commonly considered to produce structured programs. The Bourne shell led to the development of the KornShell (ksh), Almquist shell (ash), and the popular Bourne-again shell (or Bash).


title: Command-line interface

text: Early microcomputers themselves were based on a command-line interface such as CP/M, DOS or AppleSoft BASIC. During the 1980s and 1990s, the introduction of the Apple Macintosh and of Microsoft Windows on PCs saw the command line interface as the primary user interface replaced by the Graphical User Interface. The command line remained available as an alternative user interface, often used by system administrators and other advanced users for system administration, computer programming and batch processing.


title: Command-line interface

text: In November 2006, Microsoft released version 1.0 of Windows PowerShell (formerly codenamed "Monad"), which combined features of traditional Unix shells with their proprietary object-oriented .NET Framework. MinGW and Cygwin are open-source packages for Windows that offer a Unix-like CLI. Microsoft provides MKS Inc.'s ksh implementation "MKS Korn shell" for Windows through their Services for UNIX add-on.


title: Command-line interface

text: Since 2001, the Macintosh operating system macOS has been based on a Unix-like operating system called Darwin. On these computers, users can access a Unix-like command-line interface by running the terminal emulator program called Terminal, which is found in the Utilities sub-folder of the Applications folder, or by remotely logging into the machine using ssh. Z shell is the default shell for macOS; Bash, tcsh, and the KornShell are also provided. Before macOS Catalina, Bash was the default.


title: Command-line interface

text: A CLI is used whenever a large vocabulary of commands or queries, coupled with a wide (or arbitrary) range of options, can be entered more rapidly as text than with a pure GUI. This is typically the case with s. CLIs are also used by systems with insufficient resources to support a graphical user interface. Some computer language systems (such as Python, Forth, LISP, Rexx, and many dialects of BASIC) provide an interactive command-line mode to allow for rapid evaluation of code.


title: Command-line interface

text: CLIs are often used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users. CLIs are also popular among people with visual disabilities since the commands and responses can be displayed using refreshable Braille displays.


title: Command-line interface

text: In this format, the delimiters between command-line elements are whitespace characters and the end-of-line delimiter is the newline delimiter. This is a widely used (but not universal) convention.


title: Command-line interface

text: A CLI can generally be considered as consisting of syntax and semantics. The "syntax" is the grammar that all commands must follow. In the case of operating systems, DOS and Unix each define their own set of rules that all commands must follow. In the case of embedded systems, each vendor, such as Nortel, Juniper Networks or Cisco Systems, defines their own proprietary set of rules. These rules also dictate how a user navigates through the system of commands. The "semantics" define what sort of operations are possible, on what sort of data these operations can be performed, and how the grammar represents these operations and data—the symbolic meaning in the syntax.


title: Command-line interface

text: Two different CLIs may agree on either syntax or semantics, but it is only when they agree on both that they can be considered sufficiently similar to allow users to use both CLIs without needing to learn anything, as well as to enable re-use of scripts.


title: Command-line interface

text: A simple CLI will display a prompt, accept a "command line" typed by the user terminated by the Enter key, then execute the specified command and provide textual display of results or error messages. Advanced CLIs will validate, interpret and parameter-expand the command line before executing the specified command, and optionally capture or redirect its output.


title: Command-line interface

text: Unlike a button or menu item in a GUI, a command line is typically self-documenting, stating exactly what the user wants done. In addition, command lines usually include many defaults that can be changed to customize the results. Useful command lines can be saved by assigning a character string or alias to represent the full command, or several commands can be grouped to perform a more complex sequence – for instance, compile the program, install it, and run it — creating a single entity, called a command procedure or script which itself can be treated as a command. These advantages mean that a user must figure out a complex command or series of commands only once, because they can be saved, to be used again.


title: Command-line interface

text: where "doSomething" is, in effect, a verb, "how" an adverb (for example, should the command be executed "verbosely" or "quietly") and "toFiles" an object or objects (typically one or more files) on which the command should act. The codice_1 in the third example is a redirection operator, telling the command-line interpreter to send the output of the command not to its own standard output (the screen) but to the named file. This will overwrite the file. Using codice_2 will redirect the output and append it to the file. Another redirection operator is the vertical bar (codice_3), which creates a pipeline where the output of one command becomes the input to the next command.


title: Command-line interface

text: One can modify the set of available commands by modifying which paths appear in the PATH environment variable. Under Unix, commands also need be marked as executable files. The directories in the path variable are searched in the order they are given. By re-ordering the path, one can run e.g. \OS2\MDOS\E.EXE instead of \OS2\E.EXE, when the default is the opposite. Renaming of the executables also works: people often rename their favourite editor to EDIT, for example.


title: Command-line interface

text: The command line allows one to restrict available commands, such as access to advanced internal commands. The Windows CMD.EXE does this. Often, shareware programs will limit the range of commands, including printing a command 'your administrator has disabled running batch files' from the prompt.


title: Command-line interface

text: Some CLIs, such as those in network routers, have a hierarchy of modes, with a different set of commands supported in each mode. The set of commands are grouped by association with security, system, interface, etc. In these systems the user might traverse through a series of sub-modes. For example, if the CLI had two modes called "interface" and "system", the user might use the command "interface" to enter the interface mode. At this point, commands from the system mode may not be accessible until the user exits the interface mode and enters the system mode.


title: Command-line interface

text: A command prompt (or just "prompt") is a sequence of (one or more) characters used in a command-line interface to indicate readiness to accept commands. It literally s the user to take action. A prompt usually ends with one of the characters codice_4, codice_5, codice_6, codice_7, codice_1 or codice_9 and often includes other information, such as the path of the current working directory and the hostname.


title: Command-line interface

text: On many Unix and derivative systems, the prompt commonly ends in codice_4 or codice_5 if the user is a normal user, but in codice_6 if the user is a superuser ("root" in Unix terminology).


title: Command-line interface

text: End-users can often modify prompts. Depending on the environment, they may include colors, special characters, and other elements (like variables and functions for the current time, user, shell number or working directory) in order, for instance, to make the prompt more informative or visually pleasing, to distinguish sessions on various machines, or to indicate the current level of nesting of commands. On some systems, special tokens in the definition of the prompt can be used to cause external programs to be called by the command-line interpreter while displaying the prompt.


title: Command-line interface

text: In DOS' COMMAND.COM and in Windows NT's cmd.exe users can modify the prompt by issuing a codice_13 command or by directly changing the value of the corresponding codice_14 environment variable. The default of most modern systems, the codice_15 style is obtained, for instance, with codice_16. The default of older DOS systems, codice_17 is obtained by just codice_13, although on some systems this produces the newer codice_15 style, unless used on floppy drives A: or B:; on those systems codice_20 can be used to override the automatic default and explicitly switch to the older style.


title: Command-line interface

text: Many Unix systems feature the codice_21 variable (Prompt String 1), although other variables also may affect the prompt (depending on the shell used). In the Bash shell, a prompt of the form:


title: Command-line interface

text: In zsh the codice_22 variable controls an optional "prompt" on the right-hand side of the display. It is not a real prompt in that the location of text entry does not change. It is used to display information on the same line as the prompt, but right-justified.


title: Command-line interface

text: In RISC OS the command prompt is a codice_23 symbol, and thus (OS) CLI commands are often referred to as "star commands". One can also access the same commands from other command lines (such as the BBC BASIC command line), by preceding the command with a codice_23.


title: Command-line interface

text: A command-line argument or parameter is an item of information provided to a program when it is started. A program can have many command-line arguments that identify sources or destinations of information, or that alter the operation of the program.


title: Command-line interface

text: When a command processor is active a program is typically invoked by typing its name followed by command-line arguments (if any). For example, in Unix and Unix-like environments, an example of a command-line argument is:


title: Command-line interface

text: Some programming languages, such as C, C++ and Java, allow a program to interpret the command-line arguments by handling them as string parameters in the main function. Other languages, such as Python, expose operating system specific API (functionality) through codice_25 module, and in particular codice_26 for "command-line arguments".


title: Command-line interface

text: In Unix-like operating systems, a single hyphen used in place of a file name is a special value specifying that a program should handle data coming from the standard input or send data to the standard output.


title: Command-line interface

text: A command-line option or simply option (also known as a flag or switch) modifies the operation of a command; the effect is determined by the command's program. Options follow the command name on the command line, separated by spaces. A space before the first option is not always required, such as codice_27 and codice_28 in DOS, which have the same effect of listing the DIR command's available options, whereas codice_29 (in many versions of Unix) "does" require the option to be preceded by at least one space (and is case-sensitive).


title: Command-line interface

text: The format of options varies widely between operating systems. In most cases the syntax is by convention rather than an operating system requirement; the entire command line is simply a string passed to a program, which can process it in any way the programmer wants, so long as the interpreter can tell where the command name ends and its arguments and options begin.


title: Command-line interface

text: A few representative samples of command-line options, all relating to listing files in a directory, to illustrate some conventions:


title: Command-line interface

text: In Multics, command-line options and subsystem keywords may be abbreviated. This idea appears to derive from the PL/I programming language, with its shortened keywords (e.g., STRG for STRINGRANGE and DCL for DECLARE). For example, in the Multics "forum" subsystem, the "-long_subject" parameter can be abbreviated "-lgsj". It is also common for Multics commands to be abbreviated, typically corresponding to the initial letters of the words that are strung together with underscores to form command names, such as the use of "did" for "delete_iacl_dir".


title: Command-line interface

text: In some other systems abbreviations are automatic, such as permitting enough of the first characters of a command name to uniquely identify it (such as codice_30 as an abbreviation for codice_31) while others may have some specific abbreviations pre-programmed (e.g. codice_32 for codice_33 in COMMAND.COM) or user-defined via batch scripts and aliases (e.g. codice_34 in tcsh).


title: Command-line interface

text: On DOS, OS/2 and Windows, different programs called from their COMMAND.COM or CMD.EXE (or internal their commands) may use different syntax within the same operating system. For example:


title: Command-line interface

text: In DOS, OS/2 and Windows, the forward slash (codice_35) is most prevalent, although the hyphen-minus is also sometimes used. In many versions of DOS (MS-DOS/PC DOS 2.xx and higher, all versions of DR-DOS since 5.0, as well as PTS-DOS, Embedded DOS, FreeDOS and RxDOS) the switch character (sometimes abbreviated switchar or switchchar) to be used is defined by a value returned from a system call (INT 21h/AX=3700h). The default character returned by this API is codice_35, but can be changed to a hyphen-minus on the above-mentioned systems, except for under Datalight ROM-DOS and MS-DOS/PC DOS 5.0 and higher, which always return codice_35 from this call (unless one of many available TSRs to reenable the SwitChar feature is loaded). In some of these systems (MS-DOS/PC DOS 2.xx, DOS Plus 2.1, DR-DOS 7.02 and higher, PTS-DOS, Embedded DOS, FreeDOS and RxDOS), the setting can also be pre-configured by a SWITCHAR directive in CONFIG.SYS. General Software's Embedded DOS provides a SWITCH command for the same purpose, whereas 4DOS allows the setting to be changed via codice_48. Under DR-DOS, if the setting has been changed from codice_35, the first directory separator codice_50 in the display of the PROMPT parameter codice_51 will change to a forward slash codice_35 (which is also a valid directory separator in DOS, FlexOS, 4680 OS, 4690 OS, OS/2 and Windows) thereby serving as a visual clue to indicate the change. Also, the current setting is reflected also in the built-in help screens. Some versions of DR-DOS COMMAND.COM also support a PROMPT token codice_53 to display the current setting. COMMAND.COM since DR-DOS 7.02 also provides a pseudo-environment variable named codice_54 to allow portable batchjobs to be written. Several external DR-DOS commands additionally support an environment variable codice_55 to override the system setting.


title: Command-line interface

text: However, many programs are hardwired to use codice_35 only, rather than retrieving the switch setting before parsing command-line arguments. A very small number, mainly ports from Unix-like systems, are programmed to accept "-" even if the switch character is not set to it (for example codice_57 and codice_58, supplied with Microsoft Windows, will accept the /? option to list available options, and yet the list will specify the "-" convention).


title: Command-line interface

text: In Unix-like systems, the ASCII hyphen-minus begins options; the new (and GNU) convention is to use "two" hyphens then a word (e.g. codice_59) to identify the option's use while the old convention (and still available as an option for frequently-used options) is to use one hyphen then one letter (e.g., codice_60); if one hyphen is followed by two or more letters it may mean two options are being specified, or it may mean the second and subsequent letters are a parameter (such as filename or date) for the first option.


title: Command-line interface

text: Two hyphen-minus characters without following letters (codice_61) may indicate that the remaining arguments should not be treated as options, which is useful for example if a file name itself begins with a hyphen, or if further arguments are meant for an inner command (e.g., sudo). Double hyphen-minuses are also sometimes used to prefix "long options" where more descriptive option names are used. This is a common feature of GNU software. The "getopt" function and program, and the "getopts" command are usually used for parsing command-line options.


title: Command-line interface

text: Unix command names, arguments and options are case-sensitive (except in a few examples, mainly where popular commands from other operating systems have been ported to Unix).


title: Command-line interface

text: Conversational Monitor System (CMS) uses a single left parenthesis to separate options at the end of the command from the other arguments. For example, in the following command the options indicate that the target file should be replaced if it exists, and the date and time of the source file should be retained on the copy:


title: Command-line interface

text: Data General's CLI under their RDOS, AOS, etc. operating systems, as well as the version of CLI that came with their Business Basic, uses only codice_35 as the switch character, is case-insensitive, and allows "local switches" on some arguments to control the way they are interpreted, such as codice_66 has the global option "U" to the macro assembler command to append user symbols, but two local switches, one to specify LIB should be skipped on pass 2 and the other to direct listing to the printer, $LPT.


title: Command-line interface

text: One of the criticisms of a CLI is the lack of cues to the user as to the available actions. In contrast, GUIs usually inform the user of available actions with menus, icons, or other visual cues. To overcome this limitation, many CLI programs display a usage message, typically when invoked with no arguments or one of codice_67, codice_68, codice_69, codice_70, codice_71, codice_72, codice_73, codice_74, codice_75, or codice_76.


title: Command-line interface

text: However, entering a program name without parameters in the hope that it will display usage help can be hazardous, as programs and scripts for which command line arguments are optional will execute without further notice.


title: Command-line interface

text: Although desirable at least for the help parameter, programs may not support all option lead-in characters exemplified above.


title: Command-line interface

text: Under DOS, where the default command-line option character can be changed from codice_35 to codice_9, programs may query the SwitChar API in order to determine the current setting. So, if a program is not hardwired to support them all, a user may need to know the current setting even to be able to reliably request help.


title: Command-line interface

text: If the SwitChar has been changed to codice_9 and therefore the codice_35 character is accepted as alternative path delimiter also at the DOS command line, programs may misinterpret options like codice_72 or codice_73 as paths rather than help parameters. However, if given as first or only parameter, most DOS programs will, by convention, accept it as request for help regardless of the current SwitChar setting.


title: Command-line interface

text: In some cases, different levels of help can be selected for a program. Some programs supporting this allow to give a verbosity level as an optional argument to the help parameter (as in codice_83, codice_84, etc.) or they give just a short help on help parameters with question mark and a longer help screen for the other help options.


title: Command-line interface

text: Depending on the program, additional or more specific help on accepted parameters is sometimes available by either providing the parameter in question as an argument to the help parameter or vice versa (as in codice_85 or in codice_86 (assuming codice_87 would be another parameter supported by the program)).


title: Command-line interface

text: In a similar fashion to the help parameter, but much less common, some programs provide additional information about themselves (like mode, status, version, author, license or contact information) when invoked with an "about" parameter like codice_88, codice_89, codice_90, or codice_91.


title: Command-line interface

text: Since the codice_67 and codice_93 characters typically also serve other purposes at the command line, they may not be available in all scenarios, therefore, they should not be the only options to access the corresponding help information.


title: Command-line interface

text: If more detailed help is necessary than provided by a program's built-in internal help, many systems support a dedicated external "codice_94" command (or similar), which accepts a command name as calling parameter and will invoke an external help system.


title: Command-line interface

text: In the DR-DOS family, typing codice_71 or codice_73 at the COMMAND.COM prompt instead of a command itself will display a dynamically generated list of available internal commands; 4DOS and NDOS support the same feature by typing codice_67 at the prompt (which is also accepted by newer versions of DR-DOS COMMAND.COM); internal commands can be individually disabled or reenabled via codice_98. In addition to this, some newer versions of DR-DOS COMMAND.COM also accept a codice_99 command to display a list of available built-in pseudo-environment variables. Besides their purpose as quick help reference this can be used in batchjobs to query the facilities of the underlying command-line processor.


title: Command-line interface

text: Notice that these characters have different meanings than when used directly in the shell. Angle brackets may be omitted when confusing the parameter name with a literal string is not likely.


title: Command-line interface

text: In many areas of computing, but particularly in the command line, the space character can cause problems as it has two distinct and incompatible functions: as part of a command or parameter, or as a parameter or name separator. Ambiguity can be prevented either by prohibiting embedded spaces in file and directory names in the first place (for example, by substituting them with underscores codice_104), or by enclosing a name with embedded spaces between quote characters or using an escape character before the space, usually a backslash (codice_50). For example


title: Command-line interface

text: are not ambiguous. Unix-based operating systems minimize the use of embedded spaces to minimize the need for quotes. In Microsoft Windows, one often has to use quotes because embedded spaces (such as in directory names) are common.


title: Command-line interface

text: The term command-line interpreter (CLI) is applied to computer programs designed to interpret a sequence of lines of text which may be entered by a user, read from a file or another kind of data stream. The context of interpretation is usually one of a given operating system or programming language.


title: Command-line interface

text: Command-line interpreters allow users to issue various commands in a very efficient (and often terse) way. This requires the user to know the names of the commands and their parameters, and the syntax of the language that is interpreted.


title: Command-line interface

text: The Unix codice_111 mechanism and OS/2 EXTPROC command facilitate the passing of batch files to external processors. One can use these mechanisms to write specific command processors for dedicated uses, and process external data files which reside in batch files.


title: Command-line interface

text: Many graphical interfaces, such as the OS/2 Presentation Manager and early versions of Microsoft Windows use command-lines to call helper programs to open documents and programs. The commands are stored in the graphical shell or in files like the registry or the OS/2 codice_112 file.


title: Command-line interface

text: The earliest computers did not support interactive input/output devices, often relying on sense switches and lights to communicate with the computer operator. This was adequate for batch systems that ran one program at a time, often with the programmer acting as operator. This also had the advantage of low overhead, since lights and switches could be tested and set with one machine instruction. Later a single system console was added to allow the operator to communicate with the system.


title: Command-line interface

text: From the 1960s onwards, user interaction with computers was primarily by means of command-line interfaces, initially on machines like the Teletype Model 33 ASR, but then on early CRT-based computer terminals such as the VT52.


title: Command-line interface

text: All of these devices were purely text based, with no ability to display graphic or pictures. For business application programs, text-based menus were used, but for more general interaction the command line was the interface.


title: Command-line interface

text: Around 1964 Louis Pouzin introduced the concept and the name "shell" in Multics, building on earlier, simpler facilities in the Compatible Time-Sharing System (CTSS).


title: Command-line interface

text: From the early 1970s the Unix operating system adapted the concept of a powerful command-line environment, and introduced the ability to "pipe" the output of one command in as input to another. Unix also had the capability to save and re-run strings of commands as "shell scripts" which acted like custom commands.


title: Command-line interface

text: The command-line was also the main interface for the early home computers such as the Commodore PET, Apple II and BBC Micro – almost always in the form of a BASIC interpreter. When more powerful business oriented microcomputers arrived with CP/M and later DOS computers such as the IBM PC, the command-line began to borrow some of the syntax and features of the Unix shells such as globbing and piping of output.


title: Command-line interface

text: The command-line was first seriously challenged by the PARC GUI approach used in the 1983 Apple Lisa and the 1984 Apple Macintosh. A few computer users used GUIs such as GEOS and Windows 3.1 but the majority of IBM PC users did not replace their COMMAND.COM shell with a GUI until Windows 95 was released in 1995.


title: Command-line interface

text: While most non-expert computer users now use a GUI almost exclusively, more advanced users have access to powerful command-line environments:


title: Command-line interface

text: Most command-line interpreters support scripting, to various extents. (They are, after all, interpreters of an interpreted programming language, albeit in many cases the language is unique to the particular command-line interpreter.) They will interpret scripts (variously termed shell scripts or batch files) written in the language that they interpret. Some command-line interpreters also incorporate the interpreter engines of other languages, such as REXX, in addition to their own, allowing the executing of scripts, in those languages, directly within the command-line interpreter itself.


title: Command-line interface

text: Conversely, scripting programming languages, in particular those with an eval function (such as REXX, Perl, Python, Ruby or Jython), can be used to implement command-line interpreters and filters. For a few operating systems, most notably DOS, such a command interpreter provides a more flexible command-line interface than the one supplied. In other cases, such a command interpreter can present a highly customised user interface employing the user interface and input/output facilities of the language.


title: Command-line interface

text: The command line provides an interface between programs as well as the user. In this sense, a command line is an alternative to a dialog box. Editors and databases present a command line, in which alternate command processors might run. On the other hand, one might have options on the command line, which opens a dialog box. The latest version of 'Take Command' has this feature. DBase used a dialog box to construct command lines, which could be further edited before use.


title: Command-line interface

text: Programs like BASIC, diskpart, Edlin, and QBASIC all provide command-line interfaces, some of which use the system shell. Basic is modeled on the default interface for 8-bit Intel computers. Calculators can be run as command-line or dialog interfaces.


title: Command-line interface

text: Emacs provides a command-line interface in the form of its minibuffer. Commands and arguments can be entered using Emacs standard text editing support, and output is displayed in another buffer.


title: Command-line interface

text: There are a number of text mode games, like "Adventure" or "King's Quest 1-3", which relied on the user typing commands at the bottom of the screen. One controls the character by typing commands like 'get ring' or 'look'. The program returns a text which describes how the character sees it, or makes the action happen. The text adventure "The Hitchhiker's Guide to the Galaxy", a piece of interactive fiction based on Douglas Adam's book of the same name, is a teletype-style command-line game.


title: Command-line interface

text: The most notable of these interfaces is the standard streams interface, which allows the output of one command to be passed to the input of another. Text files can serve either purpose as well. This provides the interfaces of piping, filters and redirection. Under Unix, devices are files too, so the normal type of file for the shell used for stdin,stdout and stderr is a tty device file.


title: Command-line interface

text: Another command-line interface allows a shell program to launch helper programs, either to launch documents or start a program. The command is processed internally by the shell, and then passed on to another program to launch the document. The graphical interface of Windows and OS/2 rely heavily on command-lines passed through to other programs – console or graphical, which then usually process the command line without presenting a user-console.


title: Command-line interface

text: Programs like the OS/2 E editor and some other IBM editors, can process command-lines normally meant for the shell, the output being placed directly in the document window.


title: Command-line interface

text: A web browser's URL input field can be used as a command line. It can be used to "launch" web apps, , as well as perform a search. Google, which has been called "the command line of the internet" will perform a domain-specific search when it detects search parameters in a known format. This functionality is present whether the search is triggered from a browser field or on Google's website.


title: Command-line interface

text: There are JavaScript libraries that allow to write command line applications in browser as standalone Web apps or as part of bigger application. An example of such a website is the CLI interface to DuckDuckGo. There are also Web-based SSH applications, that allow to give access to server command line interface from a browser.


title: Command-line interface

text: Many video games on the PC feature a command line interface often referred to as a console. It is typically used by the game developers during development and by mod developers for debugging purposes as well as for cheating or skipping parts of the game.


title: Metre

text: The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefixed forms are also used relatively frequently.


title: Metre

text: The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's circumference is approximately  km. In 1799, the metre was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86. The current definition was adopted in 1983 and modified slightly in 2002 to clarify that the metre is a measure of proper length. From 1983 until 2019, the metre was formally defined as the length of the path travelled by light in a vacuum in of a second. After the 2019 redefinition of the SI base units, this definition was rephrased to include the definition of a second in terms of the caesium frequency .


title: Metre

text: "Metre" is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use "meter." Other West Germanic languages, such as German and Dutch, and North Germanic languages, such as Danish, Norwegian, and Swedish, likewise spell the word "Meter" or "meter".


title: Metre

text: Measuring devices (such as ammeter, speedometer) are spelled "-meter" in all variants of English. The suffix "-meter" has the same Greek origin as the unit of length.


title: Metre

text: The etymological roots of "metre" can be traced to the Greek verb () (to measure, count or compare) and noun () (a measure), which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism (as in "be measured in your response"). This range of uses is also found in Latin (), French (), English and other languages. The Greek word is derived from the Proto-Indo-European root "*meh₁-" 'to measure'. The motto () in the seal of the International Bureau of Weights and Measures (BIPM), which was a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as "Use measure!", thus calls for both measurement and moderation. The use of the word "metre" (for the French unit ) in English began at least as early as 1797.


title: Metre

text: In 1671, Jean Picard measured the length of a "seconds pendulum" and proposed a unit of measurement twice that length to be called the universal toise (French: "Toise universelle"). In 1675, Tito Livio Burattini suggested the term metre for a unit of length based on a pendulum length, but then it was discovered that the length of a seconds pendulum varies from place to place.


title: Metre

text: Since Eratosthenes, geographers had used meridian arcs to assess the size of the Earth, which in 1669, Jean Picard determined to have a radius of toises, treated as a simple sphere. In the 18th century, geodesy grew in importance as a means of empirically demonstrating the theory of gravity, which Émilie du Châtelet promoted in France in combination with Leibniz mathematical work, and because the radius of the Earth was the unit to which all celestial distances were to be referred.


title: Metre

text: As a result of the Lumières and during the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. On 7 October 1790 that commission advised the adoption of a decimal system, and on 19 March 1791 advised the adoption of the term "mètre" ("measure"), a basic unit of length, which they defined as equal to one ten-millionth of the quarter meridian, the distance between the North Pole and the Equator along the meridian through Paris. On 26 March 1791, the French National Constituent Assembly adopted the proposal.


title: Metre

text: The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which attempted to accurately measure the distance between a belfry in Dunkerque and Montjuïc castle in Barcelona at the longitude of the Paris Panthéon (see meridian arc of Delambre and Méchain). The expedition was fictionalised in Denis Guedj, "Le Mètre du Monde". Ken Alder wrote factually about the expedition in "The Measure of All Things: the seven year odyssey and hidden error that transformed the world". This portion of the Paris meridian was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator. From 1801 to 1812 France adopted this definition of the metre as its official unit of length based on results from this expedition combined with those of the Geodesic Mission to Peru. The latter was related by Larrie D. Ferreiro in "Measure of the Earth: The Enlightenment Expedition that Reshaped Our World".


title: Metre

text: In the 19th century, geodesy underwent a revolution through advances in mathematics as well as improvements in the instruments and methods of observation, for instance accounting for individual bias in terms of the personal equation. The application of the least squares method to meridian arc measurements demonstrated the importance of the scientific method in geodesy. On the other hand, the invention of the telegraph made it possible to measure parallel arcs, and the improvement of the reversible pendulum gave rise to the study of the Earth's gravitational field. A more accurate determination of the Figure of the Earth would soon result from the measurement of the Struve Geodetic Arc (1816–1855) and would have given another value for the definition of this standard of length. This did not invalidate the metre but highlighted that progress in science would allow better measurement of Earth's size and shape.


title: Metre

text: In 1832, Carl Friedrich Gauss studied the Earth's magnetic field and proposed adding the second to the basic units of the metre and the kilogram in the form of the CGS system (centimetre, gram, second). In 1836, he founded the "Magnetischer Verein", the first international scientific association, in collaboration with Alexander von Humboldt and Wilhelm Edouard Weber. The coordination of the observation of geophysical phenomena such as the Earth's magnetic field, lightning and gravity in different points of the globe stimulated the creation of the first international scientific associations. The foundation of the "Magnetischer Verein" would be followed by that of the Central European Arc Measurement (German: "Mitteleuropaïsche Gradmessung") on the initiative of Johann Jacob Baeyer in 1863, and by that of the International Meteorological Organisation whose second president, the Swiss meteorologist and physicist, Heinrich von Wild would represent Russia at the International Committee for Weights and Measures (CIPM).


title: Metre

text: In 1816, Ferdinand Rudolph Hassler was appointed first Superintendent of the Survey of the Coast. Trained in geodesy in Switzerland, France and Germany, Hassler had brought a standard metre made in Paris to the United States in 1805. He designed a baseline apparatus which instead of bringing different bars in actual contact during measurements, used only one bar calibrated on the metre and optical contact. Thus the metre became the unit of length for geodesy in the United States.


title: Metre

text: Since 1830, Hassler was also head of the Bureau of Weights and Measures which became a part of the Coast Survey. He compared various units of length used in the United States at that time and measured coefficients of expansion to assess temperature effects on the measurements.


title: Metre

text: In 1841, Friedrich Wilhelm Bessel, taking into account errors which had been recognized by Louis Puissant in the French meridian arc comprising the arc measurement of Delambre and Méchain which had been extended southward by François Arago and Jean-Baptiste Biot, recalculated the flattening of the Earth ellipsoid making use of nine more arc measurements, namely Peruan, Prussian, first East-Indian, second East-Indian, English, Hannover, Danish, Russian and Swedish covering almost 50 degrees of latitude, and stated that the Earth quadrant used for determining the length of the metre was nothing more than a rather imprecise conversion factor between the toise and the metre.


title: Metre

text: Regarding the precision of the conversion from the toise to the metre, both units of measurement were then defined by primary standards, and unique artifacts made of different alloys with distinct coefficients of expansion were the legal basis of units of length. A wrought iron ruler, the Toise of Peru, also called "Toise de l'Académie", was the French primary standard of the toise, and the metre was officially defined by the "Mètre des Archives" made of platinum. Besides the latter, another platinum and twelve iron standards of the metre were made in 1799. One of them became known as the "Committee Meter" in the United States and served as standard of length in the Coast Survey until 1890. According to geodesists, these standards were secondary standards deduced from the Toise of Peru. In Europe, surveyors continued to use measuring instruments calibrated on the Toise of Peru. Among these, the toise of Bessel and the apparatus of Borda were respectively the main references for geodesy in Prussia and in France. A French scientific instrument maker, Jean Nicolas Fortin, had made two direct copies of the Toise of Peru, the first for Friedrich Georg Wilhelm von Struve in 1821 and a second for Friedrich Bessel in 1823.


title: Metre

text: On the subject of the theoretical definition of the metre, it had been inaccessible and misleading at the time of Delambre and Mechain arc measurement, as the geoid is a ball, which on the whole can be assimilated to an oblate spheroid, but which in detail differs from it so as to prohibit any generalization and any extrapolation. As early as 1861, after Friedrich von Schubert showed that the different meridians were not of equal length, Elie Ritter, a mathematician from Geneva, deduced from a computation based on eleven meridian arcs covering 86 degrees that the meridian equation differed from that of the ellipse: the meridian was swelled about the 45th degree of latitude by a layer whose thickness was difficult to estimate because of the uncertainty of the latitude of some stations, in particular that of Montjuïc in the French meridian arc. By measuring the latitude of two stations in Barcelona, Méchain had found that the difference between these latitudes was greater than predicted by direct measurement of distance by triangulation. We know now that, in addition to other errors in the survey of Delambre and Méchain, an unfavourable vertical deflection gave an inaccurate determination of Barcelona's latitude, a metre "too short" compared to a more general definition taken from the average of a large number of arcs.


title: Metre

text: Nevertheless Ferdinand Rudolph Hassler's use of the metre in coastal survey contributed to the introduction of the Metric Act of 1866 allowing the use of the metre in the United States, and also played an important role in the choice of the metre as international scientific unit of length and the proposal by the European Arc Measurement (German: "Europäische Gradmessung") to “establish a European international bureau for weights and measures”. However, in 1866, the most important concern was that the Toise of Peru, the standard of the toise constructed in 1735 for the French Geodesic Mission to the Equator, might be so much damaged that comparison with it would be worthless, while Bessel had questioned the accuracy of copies of this standard belonging to Altona and Koenigsberg Observatories, which he had compared to each other about 1840. Indeed when the primary Imperial yard standard was partially destroyed in 1834, a new standard of reference had been constructed using copies of the "Standard Yard, 1760" instead of the pendulum's length as provided for in the Weights and Measures Act of 1824.


title: Metre

text: In 1864, Urbain Le Verrier refused to join the first general conference of the Central European Arc Measurement because the French geodetic works had to be verified.


title: Metre

text: In 1866, at the meeting of the Permanent Commission of the association in Neuchâtel, Antoine Yvon Villarceau announced that he had checked eight points of the French arc. He confirmed that the metre was too short. It then became urgent to undertake a complete revision of the meridian arc. Moreover, while the extension of the French meridian arc to the Balearic Islands (1803–1807) had seemed to confirm the length of the metre, this survey had not been secured by any baseline in Spain. For that reason, Carlos Ibáñez e Ibáñez de Ibero's announcement, at this conference, of his 1858 measurement of a baseline in Madridejos was of particular importance. Indeed surveyors determined the size of triangulation networks by measuring baselines which concordance granted the accuracy of the whole survey.


title: Metre

text: In 1867 at the second general conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth. The conference recommended the adoption of the metre in replacement of the toise and the creation of an international metre commission, according to the proposal of Johann Jacob Baeyer, Adolphe Hirsch and Carlos Ibáñez e Ibáñez de Ibero who had devised two geodetic standards calibrated on the metre for the map of Spain.


title: Metre

text: Ibáñez adopted the system which Ferdinand Rudolph Hassler used for the United States Survey of the Coast, consisting of a single standard with lines marked on the bar and microscopic measurements. Regarding the two methods by which the effect of temperature was taken into account, Ibáñez used both the bimetallic rulers, in platinum and brass, which he first employed for the central baseline of Spain, and the simple iron ruler with inlaid mercury thermometers which was utilized in Switzerland. These devices, the first of which is referred to as either Brunner apparatus or Spanish Standard, were constructed in France by Jean Brunner, then his sons. Measurement traceability between the toise and the metre was ensured by comparison of the Spanish Standard with the standard devised by Borda and Lavoisier for the survey of the meridian arc connecting Dunkirk with Barcelona.


title: Metre

text: Hassler's metrological and geodetic work also had a favourable response in Russia. In 1869, the Saint Petersburg Academy of Sciences sent to the French Academy of Sciences a report drafted by Otto Wilhelm von Struve, Heinrich von Wild and Moritz von Jacobi inviting his French counterpart to undertake joint action to ensure the universal use of the metric system in all scientific work.


title: Metre

text: In the 1870s and in light of modern precision, a series of international conferences was held to devise new metric standards. When a conflict broke out regarding the presence of impurities in the metre-alloy of 1874, a member of the Preparatory Committee since 1870 and Spanish representative at the Paris Conference in 1875, Carlos Ibáñez e Ibáñez de Ibero intervened with the French Academy of Sciences to rally France to the project to create an International Bureau of Weights and Measures equipped with the scientific means necessary to redefine the units of the metric system according to the progress of sciences.


title: Metre

text: The Metre Convention ("Convention du Mètre") of 1875 mandated the establishment of a permanent International Bureau of Weights and Measures (BIPM: ') to be located in Sèvres, France. This new organisation was to construct and preserve a prototype metre bar, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The organisation distributed such bars in 1889 at the first General Conference on Weights and Measures (CGPM: '), establishing the "International Prototype Metre" as the distance between two lines on a standard bar composed of an alloy of 90% platinum and 10% iridium, measured at the melting point of ice.


title: Metre

text: The comparison of the new prototypes of the metre with each other and with the Committee metre (French: "Mètre des Archives") involved the development of special measuring equipment and the definition of a reproducible temperature scale. The BIPM's thermometry work led to the discovery of special alloys of iron-nickel, in particular invar, for which its director, the Swiss physicist Charles-Edouard Guillaume, was granted the Nobel Prize for physics in 1920.


title: Metre

text: As Carlos Ibáñez e Ibáñez de Ibero stated, the progress of metrology combined with those of gravimetry through improvement of Kater's pendulum led to a new era of geodesy. If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs and all determinations of the force of gravity by the mean of pendulum. Metrology had to create a common unit, adopted and respected by all civilized nations.


title: Metre

text: Moreover, at that time, statisticians knew that scientific observations are marred by two distinct types of errors, constant errors on the one hand, and fortuitous errors, on the other hand. The effects of the latters can be mitigated by the least-squares method. Constant or regular errors on the contrary must be carefully avoided, because they arise from one or more causes that constantly act in the same way and have the effect of always altering the result of the experiment in the same direction. They therefore deprive of any value the observations that they impinge. However, the distinction between systematic and random errors is far from being as sharp as one might think at first assessment. In reality, there are no or very few random errors. As science progresses, the causes of certain errors are sought out, studied, their laws discovered. These errors pass from the class of random errors into that of systematic errors. The ability of the observer consists in discovering the greatest possible number of systematic errors in order to be able, once he has become acquainted with their laws, to free his results from them using a method or appropriate corrections.


title: Metre

text: For metrology the matter of expansibility was fundamental; as a matter of fact the temperature measuring error related to the length measurement in proportion to the expansibility of the standard and the constantly renewed efforts of metrologists to protect their measuring instruments against the interfering influence of temperature revealed clearly the importance they attached to the expansion-induced errors. It was thus crucial to compare at controlled temperatures with great precision and to the same unit all the standards for measuring geodetic baselines and all the pendulum rods. Only when this series of metrological comparisons would be finished with a probable error of a thousandth of a millimetre would geodesy be able to link the works of the different nations with one another, and then proclaim the result of the measurement of the Globe.


title: Metre

text: As the figure of the Earth could be inferred from variations of the seconds pendulum length with latitude, the United States Coast Survey instructed Charles Sanders Peirce in the spring of 1875 to proceed to Europe for the purpose of making pendulum experiments to chief initial stations for operations of this sort, in order to bring the determinations of the forces of gravity in America into communication with those of other parts of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe. In 1886 the association of geodesy changed name for the International Geodetic Association, which Carlos Ibáñez e Ibáñez de Ibero presided up to his death in 1891. During this period the International Geodetic Association (German: "Internationale Erdmessung") gained worldwide importance with the joining of United States, Mexico, Chile, Argentina and Japan.


title: Metre

text: Efforts to supplement the various national surveying systems, which began in the 19th century with the foundation of the "Mitteleuropäische Gradmessung", resulted in a series of global ellipsoids of the Earth (e.g., Helmert 1906, Hayford 1910 and 1924) which would later lead to develop the World Geodetic System. Nowadays the practical realisation of the metre is possible everywhere thanks to the atomic clocks embedded in GPS satellites.


title: Metre

text: In 1873, James Clerk Maxwell suggested that light emitted by an element be used as the standard both for the metre and for the second. These two quantities could then be used to define the unit of mass.


title: Metre

text: In 1893, the standard metre was first measured with an interferometer by Albert A. Michelson, the inventor of the device and an advocate of using some particular wavelength of light as a standard of length. By 1925, interferometry was in regular use at the BIPM. However, the International Prototype Metre remained the standard until 1960, when the eleventh CGPM defined the metre in the new International System of Units (SI) as equal to wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum.


title: Metre

text: To further reduce uncertainty, the 17th CGPM in 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light:


title: Metre

text: This definition fixed the speed of light in vacuum at exactly metres per second (≈ or ≈1.079 billion km/hour). An intended by-product of the 17th CGPM's definition was that it enabled scientists to compare lasers accurately using frequency, resulting in wavelengths with one-fifth the uncertainty involved in the direct comparison of wavelengths, because interferometer errors were eliminated. To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised helium–neon laser "a recommended radiation" for realising the metre. For the purpose of delineating the metre, the BIPM currently considers the HeNe laser wavelength, , to be with an estimated relative standard uncertainty ("U") of . This uncertainty is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain atomic clock (). Consequently, a realisation of the metre is usually delineated (not defined) today in labs as wavelengths of helium-neon laser light in a vacuum, the error stated being only that of frequency determination. This bracket notation expressing the error is explained in the article on measurement uncertainty.


title: Metre

text: Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source. A commonly used medium is air, and the National Institute of Standards and Technology (NIST) has set up an online calculator to convert wavelengths in vacuum to wavelengths in air. As described by NIST, in air, the uncertainties in characterising the medium are dominated by errors in measuring temperature and pressure. Errors in the theoretical formulas used are secondary. By implementing a refractive index correction such as this, an approximate realisation of the metre can be implemented in air, for example, using the formulation of the metre as wavelengths of helium–neon laser light in a vacuum, and converting the wavelengths in a vacuum to wavelengths in air. Air is only one possible medium to use in a realisation of the metre, and any partial vacuum can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented.


title: Metre

text: The metre is "defined" as the path length travelled by light in a given time, and practical laboratory length measurements in metres are determined by counting the number of wavelengths of laser light of one of the standard types that fit into the length, and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser interferometers for a length measurement:


title: Metre

text: Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon the relation


title: Metre

text: which converts the unit of wavelength "λ" to metres using "c", the speed of light in vacuum in m/s. Here "n" is the refractive index of the medium in which the measurement is made, and "f" is the measured frequency of the source. Although conversion from wavelengths to metres introduces an additional error in the overall length due to measurement error in determining the refractive index and the frequency, the measurement of frequency is one of the most accurate measurements available.


title: Metre

text: In France, the metre was adopted as an exclusive measure in 1801 under the Consulate. This continued under the First French Empire until 1812, when Napoleon decreed the introduction of the non-decimal "mesures usuelles", which remained in use in France up to 1840 in the reign of Louis Philippe. Meanwhile, the metre was adopted by the Republic of Geneva. After the joining of the canton of Geneva to Switzerland in 1815, Guillaume Henri Dufour published the first official Swiss map, for which the metre was adopted as the unit of length. Louis Napoléon Bonaparte, a Swiss–French binational officer, was present when a baseline was measured near Zürich for the Dufour map, which would win the gold medal for a national map at the Exposition Universelle of 1855. Among the scientific instruments calibrated on the metre that were displayed at the Exposition Universelle, was Brunner's apparatus, a geodetic instrument devised for measuring the central baseline of Spain, whose designer, Carlos Ibáñez e Ibáñez de Ibero would represent Spain at the International Statistical Institute. In 1885, in addition to the Exposition Universelle and the second Statistical Congress held in Paris, an International Association for Obtaining a Uniform Decimal System of Measures, Weights, and Coins was created there. Copies of the Spanish standard were made for Egypt, France and Germany. These standards were compared to each other and with the Borda apparatus, which was the main reference for measuring all geodetic bases in France. In 1869, Napoleon III convened the International Metre Commission, which was to meet in Paris in 1870. The Franco-Prussian War broke out, the Second French Empire collapsed, but the metre survived.


title: Metre

text: SI prefixes can be used to denote decimal multiples and submultiples of the metre, as shown in the table below. Long distances are usually expressed in km, astronomical units (149.6 Gm), light-years (10 Pm), or parsecs (31 Pm), rather than in Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dam", and "3 hm", respectively.


title: Metre

text: The terms "micron" and "millimicron" can be used instead of "micrometre" (μm) and "nanometre" (nm), but this practice may be discouraged.


title: Metre

text: Within this table, "inch" and "yard" mean "international inch" and "international yard" respectively, though approximate conversions in the left column hold for both international and survey units.


title: Metre

text: The ancient Egyptian cubit was about 0.5m (surviving rods are 523–529mm). Scottish and English definitions of the ell (two cubits) were 941mm (0.941m) and 1143mm (1.143m) respectively. The ancient Parisian "toise" (fathom) was slightly shorter than 2m and was standardised at exactly 2m in the mesures usuelles system, such that 1m was exactly toise. The Russian verst was 1.0668km. The Swedish mil was 10.688km, but was changed to 10km when Sweden converted to metric units.