getopt(1)



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 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 do the  parsing  (the  options
       and  the 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  the  first
       parameter is not an option (does not start with a '-', 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 shuf-
       fling and recognize optional arguments (see section  COMPATIBILITY  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
              Display help text and exit.  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 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 the -s option is
              not given, the BASH conventions are used.  Valid  arguments  are
              currently 'sh' 'bash', 'csh', and 'tcsh'.

       -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.

       -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).

       -V, --version
              Display version information and exit.  No other output is gener-
              ated.

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  typi-
       cally  the  parameters  a shell function was called with.  Care must be
       taken that each parameter the shell function  was  called  with  corre-
       sponds  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  clas-
       sified 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 (i.e. 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  (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 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 compat-
       ible  (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 gener-
       ated 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 (i.e. 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 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
       parameter as the string of short options, and all other arguments  will
       be  parsed.   It will still do parameter shuffling (i.e. all non-option
       parameters are output 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_COR-
       RECT  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/getopt/ or
       /usr/share/doc/ in the util-linux subdirectory.

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  parame-
              ters  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 cannot  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
       bash(1), tcsh(1), getopt(3)

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

util-linux                       December 2014                       GETOPT(1)

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