getopt

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 procedures, 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 com‐
       patible  with  that  of  other versions of getopt(1).  It will still do
       parameter shuffling and recognize optional arguments (see section  COM‐
       PATIBILITY for more information).

       Traditional implementations of getopt(1) are unable to cope with white‐
       space 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  interpreted  by  the
       shell  (usually by using the eval command). This has the effect of pre‐
       serving 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 out‐
              put 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 argu‐
              ment, 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 cur‐
              rently `sh' `bash', `csh', and `tcsh'.

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              Do not quote  the  output.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

       -T, --test
              Test if your getopt(1) is this enhanced version or an  old  ver‐
              sion.  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  out‐
              put 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 generated. 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  EXAM‐
       PLES).  All parsing is done by the GNU getopt(3) routines.

       The parameters are parsed from left to right. Each parameter is classi‐
       fied 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 white‐
       space 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 possibly 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 parameters. Output can be done in compati‐
       ble (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 unexpected
       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
       (compatible) mode.  Note that many other getopt(1)  implementations  do
       not support optional arguments.

       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 arguments 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  parameters  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  gener‐
       ated  with quotes around each parameter. When this output is once again
       fed to the shell (usually by a shell eval command), it  is  split  cor‐
       rectly 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 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 special 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 inter‐
       preted 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  col‐
       lected  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 param‐
       eter  as  the  string of short options, and all other arguments will be
       parsed. It will still do parameter shuffling (ie. all non-option param‐
       eters  are  outputted  at  the  end),  unless  the environment variable
       POSIXLY_CORRECT is set.

       The environment variable GETOPT_COMPATIBLE forces getopt into  compati‐
       bility mode. Setting both this environment variable and POSIXLY_CORRECT
       offers 100% compatibility for `difficult'  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 

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

AVAILABILITY
       The getopt command is part of the util-linux-ng package and  is  avail‐
       able from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.



Linux                            May 31, 1997                        GETOPT(1)