I want to understand what the backslash represents in this command. grep \.900983 table I know what the command does, it searches for the 900983 value in table, I'm just not sure of the purpose of the \ or what it does. 
What does a backslash represent when searching for decimals
grep;regular expression;quoting
. is a regular expression metacharacter which matches any single character. \ is also a regular expression metacharacter which can be used to escape any metacharacter so that it will be literally matched.and so . matches any character, but \. matches only ..printf %c900983\\n a . | grep -n .9009831:a9009832:.900983...because the . regular expression metacharacter matches a literal . or an a or any other single character, but...printf %c900983\\n a . | grep -n \.9009832:.900983