<commit_before>.\" Copyright (c) 1998 <NAME>grav
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd July 1, 1998
.Dt FETCH 3
.Os
.Sh NAME
.Nm fetchMakeURL ,
.Nm fetchParseURL ,
.Nm fetchFreeURL ,
.Nm fetchXGetURL ,
.Nm fetchGetURL ,
.Nm fetchPutURL ,
.Nm fetchStatURL ,
.Nm fetchListURL ,
.Nm fetchXGet ,
.Nm fetchGet ,
.Nm fetchPut ,
.Nm fetchStat ,
.Nm fetchList ,
.Nm fetchXGetFile ,
.Nm fetchGetFile ,
.Nm fetchPutFile ,
.Nm fetchStatFile ,
.Nm fetchListFile ,
.Nm fetchXGetHTTP ,
.Nm fetchGetHTTP ,
.Nm fetchPutHTTP ,
.Nm fetchStatHTTP ,
.Nm fetchListHTTP ,
.Nm fetchXGetFTP ,
.Nm fetchGetFTP ,
.Nm fetchPutFTP ,
.Nm fetchStatFTP ,
.Nm fetchListFTP
.Nd file transfer functions
.Sh LIBRARY
.Lb libfetch
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <stdio.h>
.Fd #include <fetch.h>
.Ft struct url *
.Fn fetchMakeURL "const char *scheme" "const char *host" "int port" "const char *doc" "const char *user" "const char *pwd"
.Ft struct url *
.Fn fetchParseURL "const char *URL"
.Ft void
.Fn fetchFreeURL "struct url *u"
.Ft FILE *
.Fn fetchXGetURL "const char *URL" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetURL "const char *URL" "const char *flags"
.Ft FILE *
.Fn fetchPutURL "const char *URL" "const char *flags"
.Ft int
.Fn fetchStatURL "const char *URL" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListURL "const char *URL" "const char *flags"
.Ft FILE *
.Fn fetchXGet "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGet "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPut "struct url *u" "const char *flags"
.Ft int
.Fn fetchStat "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchList "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetFile "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetFile "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutFile "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatFile "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListFile "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetHTTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetHTTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutHTTP "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatHTTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListHTTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetFTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetFTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutFTP "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatFTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListFTP "struct url *u" "const char *flags"
.Sh DESCRIPTION
.Pp
These functions implement a high-level library for retrieving and
uploading files using Uniform Resource Locators (URLs).
.Pp
.Fn fetchParseURL
takes a URL in the form of a null-terminated string and splits it into
its components function according to the Common Internet Scheme Syntax
detailed in RFC1738.
A regular expression which produces this syntax is:
.Bd -literal
    <scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
.Ed
.Pp
If the URL does not seem to begin with a scheme name, the following
syntax is assumed:
.Bd -literal
    ((<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
.Ed
.Pp
Note that some components of the URL are not necessarily relevant to
all URL schemes.
For instance, the file scheme only needs the <scheme> and <document>
components.
.Pp
.Fn fetchMakeURL
and
.Fn fetchParseURL
return a pointer to a
.Fa url
structure, which is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
#define URL_SCHEMELEN 16
#define URL_USERLEN 256
#define URL_PWDLEN 256

struct url {
    char	 scheme[URL_SCHEMELEN+1];
    char	 user[URL_USERLEN+1];
    char	 pwd[URL_PWDLEN+1];
    char	 host[MAXHOSTNAMELEN+1];
    int		 port;
    char	*doc;
    off_t	 offset;
    size_t	 length;
};
.Ed
.Pp
The pointer returned by
.Fn fetchMakeURL
or
.Fn fetchParseURL
should be freed using
.Fn fetchFreeURL .
.Pp
.Fn fetchXGetURL ,
.Fn fetchGetURL ,
and
.Fn fetchPutURL
constitute the recommended interface to the
.Nm fetch
library.
They examine the URL passed to them to determine the transfer
method, and call the appropriate lower-level functions to perform the
actual transfer.
.Fn fetchXGetURL
also returns the remote document's metadata in the
.Fa url_stat
structure pointed to by the
.Fa us
argument.
.Pp
The 
.Fa flags
argument is a string of characters which specify transfer options.
The
meaning of the individual flags is scheme-dependent, and is detailed
in the appropriate section below.
.Pp
.Fn fetchStatURL
attempts to obtain the requested document's metadata and fill in the
structure pointed to by its second argument.
The
.Fa url_stat
structure is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
struct url_stat {
    off_t	 size;
    time_t	 atime;
    time_t	 mtime;
};
.Ed
.Pp
If the size could not be obtained from the server, the
.Fa size
field is set to -1.
If the modification time could not be obtained from the server, the
.Fa mtime
field is set to the epoch.
If the access time could not be obtained from the server, the
.Fa atime
field is set to the modification time.
.Pp
.Fn fetchListURL
attempts to list the contents of the directory pointed to by the URL
provided.
If successful, it returns a malloced array of
.Fa url_ent
structures.
The
.Fa url_ent
structure is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
struct url_ent {
    char         name[MAXPATHLEN];
    struct url_stat stat;
};
.Ed
.Pp
The list is terminated by an entry with an empty name.
.Pp
The pointer returned by
.Fn fetchListURL
should be freed using
.Fn free .
.Pp
.Fn fetchXGet ,
.Fn fetchGet ,
.Fn fetchPut
and
.Fn fetchStat
are similar to
.Fn fetchXGetURL ,
.Fn fetchGetURL ,
.Fn fetchPutURL
and
.Fn fetchStatURL ,
except that they expect a pre-parsed URL in the form of a pointer to
a
.Fa struct url
rather than a string.
.Pp
All of the
.Fn fetchXGetXXX ,
.Fn fetchGetXXX
and
.Fn fetchPutXXX
functions return a pointer to a stream which can be used to read or
write data from or to the requested document, respectively.
Note that
although the implementation details of the individual access methods
vary, it can generally be assumed that a stream returned by one of the
.Fn fetchXGetXXX
or
.Fn fetchGetXXX
functions is read-only, and that a stream returned by one of the
.Fn fetchPutXXX
functions is write-only.
.Sh FILE SCHEME
.Fn fetchXGetFile ,
.Fn fetchGetFile
and
.Fn fetchPutFile
provide access to documents which are files in a locally mounted file
system.
Only the <document> component of the URL is used.
.Pp
.Fn fetchXGetFile
and
.Fn fetchGetFile
do not accept any flags.
.Pp
.Fn fetchPutFile
accepts the
.Fa a
(append to file) flag.
If that flag is specified, the data written to
the stream returned by
.Fn fetchPutFile
will be appended to the previous contents of the file, instead of
replacing them.
.Sh FTP SCHEME
.Fn fetchXGetFTP ,
.Fn fetchGetFTP
and
.Fn fetchPutFTP
implement the FTP protocol as described in RFC959.
.Pp
If the
.Fa p
(passive) flag is specified, a passive (rather than active) connection
will be attempted.
.Pp
If the
.Fa l
(low) flag is specified, data sockets will be allocated in the low (or
default) port range instead of the hifh port range (see
.Xr ip 4 ) .
.Pp
If the
.Fa d
(direct) flag is specified,
.Fn fetchXGetFTP ,
.Fn fetchGetFTP
and
.Fn fetchPutFTP
will use a direct connection even if a proxy server is defined.
.Pp
If no user name or password is given, the
.Nm fetch
library will attempt an anonymous login, with user name "anonymous"
and password "anonymous@<hostname>".
.Sh HTTP SCHEME
The
.Fn fetchXGetHTTP ,
.Fn fetchGetHTTP
and
.Fn fetchPutHTTP
functions implement the HTTP/1.1 protocol.
With a little luck, there's
even a chance that they comply with RFC2068.
.Pp
If the
.Fa d
(direct) flag is specified,
.Fn fetchXGetHTTP ,
.Fn fetchGetHTTP
and
.Fn fetchPutHTTP
will use a direct connection even if a proxy server is defined.
.Pp
Since there seems to be no good way of implementing the HTTP PUT
method in a manner consistent with the rest of the
.Nm fetch
library,
.Fn fetchPutHTTP
is currently unimplemented.
.Sh RETURN VALUES
.Fn fetchParseURL
returns a pointer to a
.Fa struct url
containing the individual components of the URL.
If it is
unable to allocate memory, or the URL is syntactically incorrect,
.Fn fetchParseURL
returns a NULL pointer.
.Pp
The 
.Fn fetchStat
functions return 0 on success and -1 on failure.
.Pp
All other functions return a stream pointer which may be used to
access the requested document, or NULL if an error occurred.
.Pp
The following error codes are defined in
.Aq Pa fetch.h :
.Bl -tag -width 18n
.It Bq Er FETCH_ABORT
Operation aborted    
.It Bq Er FETCH_AUTH
Authentication failed    
.It Bq Er FETCH_DOWN
Service unavailable    
.It Bq Er FETCH_EXISTS
File exists    
.It Bq Er FETCH_FULL
File system full   
.It Bq Er FETCH_INFO
Informational response    
.It Bq Er FETCH_MEMORY
Insufficient memory    
.It Bq Er FETCH_MOVED
File has moved   
.It Bq Er FETCH_NETWORK
Network error    
.It Bq Er FETCH_OK
No error    
.It Bq Er FETCH_PROTO
Protocol error    
.It Bq Er FETCH_RESOLV
Resolver error    
.It Bq Er FETCH_SERVER
Server error    
.It Bq Er FETCH_TEMP
Temporary error    
.It Bq Er FETCH_TIMEOUT
Operation timed out   
.It Bq Er FETCH_UNAVAIL
File is not available  
.It Bq Er FETCH_UNKNOWN
Unknown error    
.It Bq Er FETCH_URL
Invalid URL
.El
.Pp
The accompanying error message includes a protocol-specific error code
and message, e.g. "File is not available (404 Not Found)"
.Sh ENVIRONMENT
.Bl -tag -width FTP_PASSIVE_MODE
.It Ev FTP_LOGIN
Default FTP login if none was provided in the URL.
.It Ev FTP_PASSIVE_MODE
If set to anything but
.Ql no ,
forces the FTP code to use passive mode.
.It Ev FTP_PASSWORD
Default FTP password if the remote server requests one and none was
provided in the URL.
.It Ev FTP_PROXY
URL of the proxy to use for FTP requests.
The document part is ignored.
FTP and HTTP proxies are supported; if no scheme is specified, FTP is
assumed.
If the proxy is an FTP proxy,
.Nm libfetch
will send
.Ql user@host
as user name to the proxy, where
.Ql user
is the real user name, and
.Ql host
is the name of the FTP server.
.Pp
If this variable is set to an empty string, no proxy will be used for
FTP requests, even if the
.Ev HTTP_PROXY
variable is set.
.It Ev ftp_proxy
Same as
.Ev FTP_PROXY ,
for compatibility.
.It Ev HTTP_AUTH
Specifies HTTP authorization parameters as a colon-separated list of
items.
The first and second item are the authorization scheme and realm
respectively; further items are scheme-dependent.
Currently, only basic authorization is supported.
.Pp
Basic authorization requires two parameters: the user name and
password, in that order.
.Pp
This variable is only used if the server requires authorization and
no user name or password was specified in the URL.
.It Ev HTTP_PROXY
URL of the proxy to use for HTTP requests.
The document part is ignored.
Only HTTP proxies are supported for HTTP requests.
If no port number is specified, the default is 3128.
.Pp
Note that this proxy will also be used for FTP documents, unless the
.Ev FTP_PROXY
variable is set.
.It Ev http_proxy
Same as
.Ev HTTP_PROXY ,
for compatibility.
.It Ev HTTP_PROXY_AUTH
Specifies authorization parameters for the HTTP proxy in the same
format as the
.Ev HTTP_AUTH
variable.
.Pp
This variable is used if and only if connected to an HTTP proxy, and
is ignored if a user and/or a password were specified in the proxy
URL.
.El
.Sh SEE ALSO
.Xr fetch 1 ,
.Xr ftpio 3 ,
.Xr ip 4
.Rs
.%A <NAME>
.%A <NAME>
.%D October 1985
.%B File Transfer Protocol
.%O RFC959
.Re
.Rs
.%A P. Deutsch
.%A A. Emtage
.%A A. Marine.
.%D May 1994
.%T How to Use Anonymous FTP
.%O RFC1635
.Re
.Rs
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%D December 1994
.%T Uniform Resource Locators (URL)
.%O RFC1738
.Re
.Rs
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%D Januray 1997
.%B Hypertext Transfer Protocol -- HTTP/1.1
.%O RFC2068
.Re
.Sh HISTORY
The
.Nm fetch
library first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm fetch
library was mostly written by
.An <NAME>\(:<NAME>\(/orgrav Aq <EMAIL>
with numerous suggestions from
.An <NAME> Aq <EMAIL> ,
.An <NAME> Aq <EMAIL>
and other
.Fx
developers.
It replaces the older
.Nm ftpio
library written by
.An <NAME> Aq <EMAIL>
and
.An <NAME> Aq <EMAIL> .
.Pp
This manual page was written by<commit_msg>Document the authentication callback interface. Update RFC references (should have done that ages ago...)<commit_after>.\" Copyright (c) 1998 <NAME>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd July 1, 1998
.Dt FETCH 3
.Os
.Sh NAME
.Nm fetchMakeURL ,
.Nm fetchParseURL ,
.Nm fetchFreeURL ,
.Nm fetchXGetURL ,
.Nm fetchGetURL ,
.Nm fetchPutURL ,
.Nm fetchStatURL ,
.Nm fetchListURL ,
.Nm fetchXGet ,
.Nm fetchGet ,
.Nm fetchPut ,
.Nm fetchStat ,
.Nm fetchList ,
.Nm fetchXGetFile ,
.Nm fetchGetFile ,
.Nm fetchPutFile ,
.Nm fetchStatFile ,
.Nm fetchListFile ,
.Nm fetchXGetHTTP ,
.Nm fetchGetHTTP ,
.Nm fetchPutHTTP ,
.Nm fetchStatHTTP ,
.Nm fetchListHTTP ,
.Nm fetchXGetFTP ,
.Nm fetchGetFTP ,
.Nm fetchPutFTP ,
.Nm fetchStatFTP ,
.Nm fetchListFTP
.Nd file transfer functions
.Sh LIBRARY
.Lb libfetch
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <stdio.h>
.Fd #include <fetch.h>
.Ft struct url *
.Fn fetchMakeURL "const char *scheme" "const char *host" "int port" "const char *doc" "const char *user" "const char *pwd"
.Ft struct url *
.Fn fetchParseURL "const char *URL"
.Ft void
.Fn fetchFreeURL "struct url *u"
.Ft FILE *
.Fn fetchXGetURL "const char *URL" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetURL "const char *URL" "const char *flags"
.Ft FILE *
.Fn fetchPutURL "const char *URL" "const char *flags"
.Ft int
.Fn fetchStatURL "const char *URL" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListURL "const char *URL" "const char *flags"
.Ft FILE *
.Fn fetchXGet "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGet "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPut "struct url *u" "const char *flags"
.Ft int
.Fn fetchStat "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchList "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetFile "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetFile "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutFile "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatFile "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListFile "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetHTTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetHTTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutHTTP "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatHTTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListHTTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchXGetFTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft FILE *
.Fn fetchGetFTP "struct url *u" "const char *flags"
.Ft FILE *
.Fn fetchPutFTP "struct url *u" "const char *flags"
.Ft int
.Fn fetchStatFTP "struct url *u" "struct url_stat *us" "const char *flags"
.Ft struct url_ent *
.Fn fetchListFTP "struct url *u" "const char *flags"
.Sh DESCRIPTION
.Pp
These functions implement a high-level library for retrieving and
uploading files using Uniform Resource Locators (URLs).
.Pp
.Fn fetchParseURL
takes a URL in the form of a null-terminated string and splits it into
its components function according to the Common Internet Scheme Syntax
detailed in RFC1738.
A regular expression which produces this syntax is:
.Bd -literal
    <scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
.Ed
.Pp
If the URL does not seem to begin with a scheme name, the following
syntax is assumed:
.Bd -literal
    ((<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
.Ed
.Pp
Note that some components of the URL are not necessarily relevant to
all URL schemes.
For instance, the file scheme only needs the <scheme> and <document>
components.
.Pp
.Fn fetchMakeURL
and
.Fn fetchParseURL
return a pointer to a
.Fa url
structure, which is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
#define URL_SCHEMELEN 16
#define URL_USERLEN 256
#define URL_PWDLEN 256

struct url {
    char	 scheme[URL_SCHEMELEN+1];
    char	 user[URL_USERLEN+1];
    char	 pwd[URL_PWDLEN+1];
    char	 host[MAXHOSTNAMELEN+1];
    int		 port;
    char	*doc;
    off_t	 offset;
    size_t	 length;
};
.Ed
.Pp
The pointer returned by
.Fn fetchMakeURL
or
.Fn fetchParseURL
should be freed using
.Fn fetchFreeURL .
.Pp
.Fn fetchXGetURL ,
.Fn fetchGetURL ,
and
.Fn fetchPutURL
constitute the recommended interface to the
.Nm fetch
library.
They examine the URL passed to them to determine the transfer
method, and call the appropriate lower-level functions to perform the
actual transfer.
.Fn fetchXGetURL
also returns the remote document's metadata in the
.Fa url_stat
structure pointed to by the
.Fa us
argument.
.Pp
The 
.Fa flags
argument is a string of characters which specify transfer options.
The
meaning of the individual flags is scheme-dependent, and is detailed
in the appropriate section below.
.Pp
.Fn fetchStatURL
attempts to obtain the requested document's metadata and fill in the
structure pointed to by its second argument.
The
.Fa url_stat
structure is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
struct url_stat {
    off_t	 size;
    time_t	 atime;
    time_t	 mtime;
};
.Ed
.Pp
If the size could not be obtained from the server, the
.Fa size
field is set to -1.
If the modification time could not be obtained from the server, the
.Fa mtime
field is set to the epoch.
If the access time could not be obtained from the server, the
.Fa atime
field is set to the modification time.
.Pp
.Fn fetchListURL
attempts to list the contents of the directory pointed to by the URL
provided.
If successful, it returns a malloced array of
.Fa url_ent
structures.
The
.Fa url_ent
structure is defined as follows in
.Aq Pa fetch.h :
.Bd -literal
struct url_ent {
    char         name[MAXPATHLEN];
    struct url_stat stat;
};
.Ed
.Pp
The list is terminated by an entry with an empty name.
.Pp
The pointer returned by
.Fn fetchListURL
should be freed using
.Fn free .
.Pp
.Fn fetchXGet ,
.Fn fetchGet ,
.Fn fetchPut
and
.Fn fetchStat
are similar to
.Fn fetchXGetURL ,
.Fn fetchGetURL ,
.Fn fetchPutURL
and
.Fn fetchStatURL ,
except that they expect a pre-parsed URL in the form of a pointer to
a
.Fa struct url
rather than a string.
.Pp
All of the
.Fn fetchXGetXXX ,
.Fn fetchGetXXX
and
.Fn fetchPutXXX
functions return a pointer to a stream which can be used to read or
write data from or to the requested document, respectively.
Note that
although the implementation details of the individual access methods
vary, it can generally be assumed that a stream returned by one of the
.Fn fetchXGetXXX
or
.Fn fetchGetXXX
functions is read-only, and that a stream returned by one of the
.Fn fetchPutXXX
functions is write-only.
.Sh FILE SCHEME
.Fn fetchXGetFile ,
.Fn fetchGetFile
and
.Fn fetchPutFile
provide access to documents which are files in a locally mounted file
system.
Only the <document> component of the URL is used.
.Pp
.Fn fetchXGetFile
and
.Fn fetchGetFile
do not accept any flags.
.Pp
.Fn fetchPutFile
accepts the
.Fa a
(append to file) flag.
If that flag is specified, the data written to
the stream returned by
.Fn fetchPutFile
will be appended to the previous contents of the file, instead of
replacing them.
.Sh FTP SCHEME
.Fn fetchXGetFTP ,
.Fn fetchGetFTP
and
.Fn fetchPutFTP
implement the FTP protocol as described in RFC959.
.Pp
If the
.Fa p
(passive) flag is specified, a passive (rather than active) connection
will be attempted.
.Pp
If the
.Fa l
(low) flag is specified, data sockets will be allocated in the low (or
default) port range instead of the hifh port range (see
.Xr ip 4 ) .
.Pp
If the
.Fa d
(direct) flag is specified,
.Fn fetchXGetFTP ,
.Fn fetchGetFTP
and
.Fn fetchPutFTP
will use a direct connection even if a proxy server is defined.
.Pp
If no user name or password is given, the
.Nm fetch
library will attempt an anonymous login, with user name "anonymous"
and password "<PASSWORD>@<hostname>".
.Sh HTTP SCHEME
The
.Fn fetchXGetHTTP ,
.Fn fetchGetHTTP
and
.Fn fetchPutHTTP
functions implement the HTTP/1.1 protocol.
With a little luck, there's
even a chance that they comply with RFC2616 and RFC2617.
.Pp
If the
.Fa d
(direct) flag is specified,
.Fn fetchXGetHTTP ,
.Fn fetchGetHTTP
and
.Fn fetchPutHTTP
will use a direct connection even if a proxy server is defined.
.Pp
Since there seems to be no good way of implementing the HTTP PUT
method in a manner consistent with the rest of the
.Nm fetch
library,
.Fn fetchPutHTTP
is currently unimplemented.
.Sh AUTHENTICATION
Apart from setting the appropriate environment variables and
specifying the user name and password in the URL or the
.Fa struct url ,
the calling program has the option of defining an authentication
function with the following prototype:
.Pp
.Ft int
.Fn myAuthMethod "struct url *u"
.Pp
The callback function should fill in the
.Fa user
and
.Fa pwd
fields in the provided
.Fa struct url
and return 0 on success, or any other value to indicate failure.
.Pp
To register the authentication callback, simply set
.Fa fetchAuthMethod
to point at it.
The callback will be used whenever a site requires authentication and
the appropriate environment variables aren't set.
.Pp
This interface is experimental and may be subject to change.
.Sh RETURN VALUES
.Fn fetchParseURL
returns a pointer to a
.Fa struct url
containing the individual components of the URL.
If it is
unable to allocate memory, or the URL is syntactically incorrect,
.Fn fetchParseURL
returns a NULL pointer.
.Pp
The 
.Fn fetchStat
functions return 0 on success and -1 on failure.
.Pp
All other functions return a stream pointer which may be used to
access the requested document, or NULL if an error occurred.
.Pp
The following error codes are defined in
.Aq Pa fetch.h :
.Bl -tag -width 18n
.It Bq Er FETCH_ABORT
Operation aborted    
.It Bq Er FETCH_AUTH
Authentication failed    
.It Bq Er FETCH_DOWN
Service unavailable    
.It Bq Er FETCH_EXISTS
File exists    
.It Bq Er FETCH_FULL
File system full   
.It Bq Er FETCH_INFO
Informational response    
.It Bq Er FETCH_MEMORY
Insufficient memory    
.It Bq Er FETCH_MOVED
File has moved   
.It Bq Er FETCH_NETWORK
Network error    
.It Bq Er FETCH_OK
No error    
.It Bq Er FETCH_PROTO
Protocol error    
.It Bq Er FETCH_RESOLV
Resolver error    
.It Bq Er FETCH_SERVER
Server error    
.It Bq Er FETCH_TEMP
Temporary error    
.It Bq Er FETCH_TIMEOUT
Operation timed out   
.It Bq Er FETCH_UNAVAIL
File is not available  
.It Bq Er FETCH_UNKNOWN
Unknown error    
.It Bq Er FETCH_URL
Invalid URL
.El
.Pp
The accompanying error message includes a protocol-specific error code
and message, e.g. "File is not available (404 Not Found)"
.Sh ENVIRONMENT
.Bl -tag -width FTP_PASSIVE_MODE
.It Ev FTP_LOGIN
Default FTP login if none was provided in the URL.
.It Ev FTP_PASSIVE_MODE
If set to anything but
.Ql no ,
forces the FTP code to use passive mode.
.It Ev FTP_PASSWORD
Default FTP password if the remote server requests one and none was
provided in the URL.
.It Ev FTP_PROXY
URL of the proxy to use for FTP requests.
The document part is ignored.
FTP and HTTP proxies are supported; if no scheme is specified, FTP is
assumed.
If the proxy is an FTP proxy,
.Nm libfetch
will send
.Ql user@host
as user name to the proxy, where
.Ql user
is the real user name, and
.Ql host
is the name of the FTP server.
.Pp
If this variable is set to an empty string, no proxy will be used for
FTP requests, even if the
.Ev HTTP_PROXY
variable is set.
.It Ev ftp_proxy
Same as
.Ev FTP_PROXY ,
for compatibility.
.It Ev HTTP_AUTH
Specifies HTTP authorization parameters as a colon-separated list of
items.
The first and second item are the authorization scheme and realm
respectively; further items are scheme-dependent.
Currently, only basic authorization is supported.
.Pp
Basic authorization requires two parameters: the user name and
password, in that order.
.Pp
This variable is only used if the server requires authorization and
no user name or password was specified in the URL.
.It Ev HTTP_PROXY
URL of the proxy to use for HTTP requests.
The document part is ignored.
Only HTTP proxies are supported for HTTP requests.
If no port number is specified, the default is 3128.
.Pp
Note that this proxy will also be used for FTP documents, unless the
.Ev FTP_PROXY
variable is set.
.It Ev http_proxy
Same as
.Ev HTTP_PROXY ,
for compatibility.
.It Ev HTTP_PROXY_AUTH
Specifies authorization parameters for the HTTP proxy in the same
format as the
.Ev HTTP_AUTH
variable.
.Pp
This variable is used if and only if connected to an HTTP proxy, and
is ignored if a user and/or a password were specified in the proxy
URL.
.El
.Sh SEE ALSO
.Xr fetch 1 ,
.Xr ftpio 3 ,
.Xr ip 4
.Rs
.%A <NAME>
.%A <NAME>
.%D October 1985
.%B File Transfer Protocol
.%O RFC959
.Re
.Rs
.%A P. Deutsch
.%A A. Emtage
.%A A. Marine.
.%D May 1994
.%T How to Use Anonymous FTP
.%O RFC1635
.Re
.Rs
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%D December 1994
.%T Uniform Resource Locators (URL)
.%O RFC1738
.Re
.Rs
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%A L. Masinter
.%A P. Leach
.%A <NAME>
.%D Januray 1999
.%B Hypertext Transfer Protocol -- HTTP/1.1
.%O RFC2616
.Re
.Rs
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%A S. Lawrence
.%A <NAME>
.%A <NAME>
.%A <NAME>
.%D June 1999
.%B HTTP Authentication: Basic and Digest Access Authentication
.%O RFC2617
.Re
.Sh HISTORY
The
.Nm fetch
library first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm fetch
library was mostly written by
.An <NAME>\(:<NAME>\(/orgrav Aq <EMAIL>
with numerous suggestions from
.An <NAME> Aq <EMAIL> ,
.An <NAME> Aq <EMAIL>
and other
.Fx
developers.
It replaces the older
.Nm ftpio
library written by
.An <NAME> Aq <EMAIL>
and
.An <NAME> Aq <EMAIL> .
.Pp
This manual page was written by
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