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Linux 2.6 - man page for getopt (linux section 1)

GETOPT(1)										GETOPT(1)

NAME
       getopt - parse command options (enhanced)

SYNOPSIS
       getopt optstring parameters
       getopt [options] [--] optstring parameters
       getopt [options] -o|--options optstring [options] [--] parameters

DESCRIPTION
       getopt is used to break up (parse) options in command lines for easy parsing by shell pro-
       cedures, and to check for legal options.  It uses the GNU getopt(3) routines to do this.

       The parameters getopt is called with can be divided into two parts: options  which  modify
       the  way  getopt  will parse (options and -o|--options optstring in the SYNOPSIS), and the
       parameters which are to be parsed (parameters in the  SYNOPSIS).   The  second  part  will
       start at the first non-option parameter that is not an option argument, or after the first
       occurrence of `--'.  If no `-o' or `--options' option is found  in  the	first  part,  the
       first parameter of the second part is used as the short options string.

       If  the environment variable GETOPT_COMPATIBLE is set, or if its first parameter is not an
       option (does not start with a `-', this is the first format in the SYNOPSIS), getopt  will
       generate  output  that  is  compatible  with that of other versions of getopt(1).  It will
       still do parameter shuffling and recognize optional arguments (see  section  COMPATIBILITY
       for more information).

       Traditional  implementations  of  getopt(1)  are  unable to cope with whitespace and other
       (shell-specific) special characters in arguments and non-option parameters. To solve  this
       problem,  this  implementation  can generate quoted output which must once again be inter-
       preted by the shell (usually by using the eval command). This has the effect of preserving
       those  characters,  but	you  must  call getopt in a way that is no longer compatible with
       other versions (the second or third format in the SYNOPSIS).  To  determine  whether  this
       enhanced version of getopt(1) is installed, a special test option (-T) can be used.

OPTIONS
       -a, --alternative
	      Allow long options to start with a single `-'.

       -h, --help
	      Output a small usage guide and exit successfully. No other output is generated.

       -l, --longoptions longopts
	      The long (multi-character) options to be recognized.  More than one option name may
	      be specified at once, by separating the names with commas. This option may be given
	      more than once, the longopts are cumulative.  Each long option name in longopts may
	      be followed by one colon to indicate it has a required argument, and by two  colons
	      to indicate it has an optional argument.

       -n, --name progname
	      The  name  that will be used by the getopt(3) routines when it reports errors. Note
	      that errors of getopt(1) are still reported as coming from getopt.

       -o, --options shortopts
	      The short (one-character) options to be recognized. If this option  is  not  found,
	      the  first parameter of getopt that does not start with a `-' (and is not an option
	      argument) is used as the short options string.   Each  short  option  character  in
	      shortopts  may be followed by one colon to indicate it has a required argument, and
	      by two colons to indicate it has an optional  argument.	The  first  character  of
	      shortopts  may  be `+' or `-' to influence the way options are parsed and output is
	      generated (see section SCANNING MODES for details).

       -q, --quiet
	      Disable error reporting by getopt(3).

       -Q, --quiet-output
	      Do not generate normal output. Errors are still reported by getopt(3),  unless  you
	      also use -q.

       -s, --shell shell
	      Set  quoting  conventions  to  those of shell. If no -s argument is found, the BASH
	      conventions are used. Valid arguments are currently `sh' `bash', `csh', and `tcsh'.

       -u, --unquoted
	      Do not quote the output. Note that whitespace and special (shell-dependent) charac-
	      ters  can  cause	havoc in this mode (like they do with other getopt(1) implementa-
	      tions).

       -T, --test
	      Test if your getopt(1) is this enhanced version or an old version.  This	generates
	      no  output, and sets the error status to 4. Other implementations of getopt(1), and
	      this version if the environment variable GETOPT_COMPATIBLE is set, will return `--'
	      and error status 0.

       -V, --version
	      Output version information and exit successfully. No other output is generated.

PARSING
       This  section  specifies  the  format  of the second part of the parameters of getopt (the
       parameters in the SYNOPSIS).  The next section (OUTPUT) describes the output that is  gen-
       erated.	These  parameters were typically the parameters a shell function was called with.
       Care must be taken that each parameter the shell function was called with  corresponds  to
       exactly	one parameter in the parameter list of getopt (see the EXAMPLES).  All parsing is
       done by the GNU getopt(3) routines.

       The parameters are parsed from left to right. Each parameter  is  classified  as  a  short
       option, a long option, an argument to an option, or a non-option parameter.

       A  simple  short option is a `-' followed by a short option character. If the option has a
       required argument, it may be written directly after the option character or  as	the  next
       parameter (ie. separated by whitespace on the command line). If the option has an optional
       argument, it must be written directly after the option character if present.

       It is possible to specify several short options after one `-', as long as all (except pos-
       sibly the last) do not have required or optional arguments.

       A  long	option normally begins with `--' followed by the long option name.  If the option
       has a required argument, it may be written directly after the long option name,	separated
       by `=', or as the next argument (ie. separated by whitespace on the command line).  If the
       option has an optional argument, it must be written directly after the long  option  name,
       separated  by `=', if present (if you add the `=' but nothing behind it, it is interpreted
       as if no argument was present; this is a slight bug, see the BUGS).  Long options  may  be
       abbreviated, as long as the abbreviation is not ambiguous.

       Each  parameter not starting with a `-', and not a required argument of a previous option,
       is a non-option parameter. Each parameter after a `--' parameter is always interpreted  as
       a  non-option  parameter.   If  the environment variable POSIXLY_CORRECT is set, or if the
       short option string started with a  `+',  all  remaining  parameters  are  interpreted  as
       non-option parameters as soon as the first non-option parameter is found.

OUTPUT
       Output is generated for each element described in the previous section.	Output is done in
       the same order as the elements are specified in the input, except for  non-option  parame-
       ters. Output can be done in compatible (unquoted) mode, or in such way that whitespace and
       other special characters within arguments and non-option  parameters  are  preserved  (see
       QUOTING).   When  the output is processed in the shell script, it will seem to be composed
       of distinct elements that can be processed one by one (by using the shift command in  most
       shell  languages).  This  is imperfect in unquoted mode, as elements can be split at unex-
       pected places if they contain whitespace or special characters.

       If there are problems parsing the parameters, for example because a required  argument  is
       not  found or an option is not recognized, an error will be reported on stderr, there will
       be no output for the offending element, and a non-zero error status is returned.

       For a short option, a single `-' and the option character are generated as one  parameter.
       If  the	option	has  an  argument, the next parameter will be the argument. If the option
       takes an optional argument, but none was found, the next parameter will be  generated  but
       be  empty in quoting mode, but no second parameter will be generated in unquoted (compati-
       ble) mode.  Note that many other getopt(1) implementations do not support  optional  argu-
       ments.

       If  several  short  options were specified after a single `-', each will be present in the
       output as a separate parameter.

       For a long option, `--' and the full option name are generated as one parameter.  This  is
       done  regardless  whether the option was abbreviated or specified with a single `-' in the
       input. Arguments are handled as with short options.

       Normally, no non-option parameters output is generated until all options and  their  argu-
       ments  have been generated. Then `--' is generated as a single parameter, and after it the
       non-option parameters in the order they were found, each as a separate parameter.  Only if
       the  first character of the short options string was a `-', non-option parameter output is
       generated at the place they are found in the input (this is not	supported  if  the  first
       format  of the SYNOPSIS is used; in that case all preceding occurrences of `-' and `+' are
       ignored).

QUOTING
       In compatible mode, whitespace or 'special' characters in arguments or non-option  parame-
       ters  are not handled correctly. As the output is fed to the shell script, the script does
       not know how it is supposed to break the output into separate parameters.   To  circumvent
       this  problem,  this  implementation  offers quoting. The idea is that output is generated
       with quotes around each parameter. When this output is once again fed to the  shell  (usu-
       ally by a shell eval command), it is split correctly into separate parameters.

       Quoting	is not enabled if the environment variable GETOPT_COMPATIBLE is set, if the first
       form of the SYNOPSIS is used, or if the option `-u' is found.

       Different shells use different quoting conventions. You can use the `-s' option to  select
       the shell you are using. The following shells are currently supported: `sh', `bash', `csh'
       and `tcsh'.  Actually, only two `flavors' are distinguished: sh-like  quoting  conventions
       and  csh-like  quoting  conventions. Chances are that if you use another shell script lan-
       guage, one of these flavors can still be used.

SCANNING MODES
       The first character of the short options string may be a `-' or a `+' to indicate  a  spe-
       cial  scanning  mode.  If the first calling form in the SYNOPSIS is used they are ignored;
       the environment variable POSIXLY_CORRECT is still examined, though.

       If the first character is `+', or if the  environment  variable	POSIXLY_CORRECT  is  set,
       parsing	stops  as  soon  as the first non-option parameter (ie. a parameter that does not
       start with a `-') is found that is not an option argument. The  remaining  parameters  are
       all interpreted as non-option parameters.

       If  the	first  character is a `-', non-option parameters are outputted at the place where
       they are found; in normal operation, they are all collected at the end of output  after	a
       `--'  parameter	has been generated. Note that this `--' parameter is still generated, but
       it will always be the last parameter in this mode.

COMPATIBILITY
       This version of getopt(1) is written to be as compatible as possible  to  other	versions.
       Usually	you  can  just replace them with this version without any modifications, and with
       some advantages.

       If the first character of the first parameter of getopt is not a  `-',  getopt  goes  into
       compatibility  mode. It will interpret its first parameter as the string of short options,
       and all other arguments will be parsed. It will still  do  parameter  shuffling	(ie.  all
       non-option  parameters  are  outputted  at  the	end),  unless  the  environment  variable
       POSIXLY_CORRECT is set.

       The environment variable GETOPT_COMPATIBLE forces getopt into compatibility mode.  Setting
       both  this  environment variable and POSIXLY_CORRECT offers 100% compatibility for `diffi-
       cult' programs. Usually, though, neither is needed.

       In compatibility mode, leading `-' and `+' characters in  the  short  options  string  are
       ignored.

RETURN CODES
       getopt returns error code 0 for successful parsing, 1 if getopt(3) returns errors, 2 if it
       does not understand its own parameters, 3 if an internal error occurs like  out-of-memory,
       and 4 if it is called with -T.

EXAMPLES
       Example	scripts  for  (ba)sh and (t)csh are provided with the getopt(1) distribution, and
       are optionally installed in /usr/share/doc/util-linux/examples.

ENVIRONMENT
       POSIXLY_CORRECT
	      This environment variable is examined by the getopt(3) routines.	 If  it  is  set,
	      parsing  stops  as  soon as a parameter is found that is not an option or an option
	      argument. All remaining parameters are also interpreted as  non-option  parameters,
	      regardless whether they start with a `-'.

       GETOPT_COMPATIBLE
	      Forces getopt to use the first calling format as specified in the SYNOPSIS.

BUGS
       getopt(3)  can parse long options with optional arguments that are given an empty optional
       argument (but can not do this for short options). This getopt(1) treats optional arguments
       that are empty as if they were not present.

       The syntax if you do not want any short option variables at all is not very intuitive (you
       have to set them explicitly to the empty string).

AUTHOR
       Frodo Looijaard <frodo@frodo.looijaard.name>

SEE ALSO
       getopt(3), bash(1), tcsh(1).

AVAILABILITY
       The getopt command is part of the util-linux package and is available from  ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux/.

Linux					   May 31, 1997 				GETOPT(1)


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