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GETOPT(1)                                 User Commands                                 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  preserv-
       ing  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 lon-
              gopts 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) char-
              acters 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 (i.e. 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 inter-
       preted  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 conven-
       tions and csh-like quoting conventions.  Chances are that if you use another shell  script
       language, 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/getopt/ or /usr/share/docs/ in util-linux subdirec-
       tory.

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  argu-
       ments 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 AT frodo.name>

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

AVAILABILITY
       The getopt command is part of the util-linux package and is available  from  Linux  Kernel
       Archive <ftp://ftp.kernel.org/pub/linux/utils/util-linux/>.



util-linux                                  June 2012                                   GETOPT(1)

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