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       getopt - Parse command line options


       #include <unistd.h>

       int getopt(int argc, char * const argv[],
                  const char *optstring);

       extern char *optarg;
       extern int optind, opterr, optopt;

       #define _GNU_SOURCE
       #include <getopt.h>

       int getopt_long(int argc, char * const argv[],
                  const char *optstring,
                  const struct option *longopts, int *longindex);

       int getopt_long_only(int argc, char * const argv[],
                  const char *optstring,
                  const struct option *longopts, int *longindex);


       The  getopt() function parses the command line arguments.  Its arguments argc and argv are
       the argument count and array as passed to the main() function on program  invocation.   An
       element  of  argv  that  starts  with  `-'  (and  is not exactly "-" or "--") is an option
       element.  The characters  of  this  element  (aside  from  the  initial  `-')  are  option
       characters.   If getopt() is called repeatedly, it returns successively each of the option
       characters from each of the option elements.

       If getopt() finds another option  character,  it  returns  that  character,  updating  the
       external  variable optind and a static variable nextchar so that the next call to getopt()
       can resume the scan with the following option character or argv-element.

       If there are no more option characters, getopt() returns -1.  Then optind is the index  in
       argv of the first argv-element that is not an option.

       optstring is a string containing the legitimate option characters.  If such a character is
       followed by a colon, the option requires an argument, so getopt places a  pointer  to  the
       following  text  in  the  same argv-element, or the text of the following argv-element, in
       optarg.  Two colons mean an option takes an optional arg; if there is text in the  current
       argv-element,  it  is  returned in optarg, otherwise optarg is set to zero.  This is a GNU
       extension.  If optstring contains W followed by a semicolon, then -W foo is treated as the
       long  option --foo.  (The -W option is reserved by POSIX.2 for implementation extensions.)
       This behaviour is a GNU extension, not available with libraries before GNU libc 2.

       By default, getopt() permutes the contents of argv as it scans, so that eventually all the
       non-options are at the end.  Two other modes are also implemented.  If the first character
       of optstring is `+' or the  environment  variable  POSIXLY_CORRECT  is  set,  then  option
       processing  stops as soon as a non-option argument is encountered.  If the first character
       of optstring is `-', then each non-option argv-element  is  handled  as  if  it  were  the
       argument  of an option with character code 1.  (This is used by programs that were written
       to expect options and other argv-elements in any order and that care about the ordering of
       the  two.)   The  special argument `--' forces an end of option-scanning regardless of the
       scanning mode.

       If getopt() does not recognize an option character, it prints an error message to  stderr,
       stores  the  character  in  optopt,  and returns `?'.  The calling program may prevent the
       error message by setting opterr to 0.

       The getopt_long() function works like getopt() except that it also accepts  long  options,
       started  out  by  two dashes.  Long option names may be abbreviated if the abbreviation is
       unique or is an exact match for some defined option.  A long option may take a  parameter,
       of the form --arg=param or --arg param.

       longopts  is  a  pointer  to  the  first  element of an array of struct option declared in
       <getopt.h> as

          struct option {
              const char *name;
              int has_arg;
              int *flag;
              int val;

       The meanings of the different fields are:

       name   is the name of the long option.

              is: no_argument (or 0) if the option does not take an  argument,  required_argument
              (or  1)  if  the  option  requires  an argument, or optional_argument (or 2) if the
              option takes an optional argument.

       flag   specifies how results are returned for a  long  option.   If  flag  is  NULL,  then
              getopt_long()  returns  val.   (For example, the calling program may set val to the
              equivalent short option character.)  Otherwise, getopt_long() returns 0,  and  flag
              points to a variable which is set to val if the option is found, but left unchanged
              if the option is not found.

       val    is the value to return, or to load into the variable pointed to by flag.

       The last element of the array has to be filled with zeroes.

       If longindex is not NULL, it points to a variable which is set to the index  of  the  long
       option relative to longopts.

       getopt_long_only()  is  like  getopt_long(),  but  `-' as well as `--' can indicate a long
       option.  If an option that starts with `-' (not `--') doesn't match  a  long  option,  but
       does match a short option, it is parsed as a short option instead.


       The  getopt()  function returns the option character if the option was found successfully,
       `:' if there was a missing parameter for one of the options, `?'  for  an  unknown  option
       character, or -1 for the end of the option list.

       getopt_long()  and getopt_long_only() also return the option character when a short option
       is recognized.  For a long option, they return val if  flag  is  NULL,  and  0  otherwise.
       Error  and  -1 returns are the same as for getopt(), plus `?' for an ambiguous match or an
       extraneous parameter.


              If this is set, then option processing stops as soon as a  non-option  argument  is

              This  variable  was used by bash 2.0 to communicate to GNU libc which arguments are
              the results of wildcard expansion and so should not be considered as options.  This
              behaviour was removed in bash version 2.01, but the support remains in GNU libc.


       The  following example program, from the source code, illustrates the use of getopt_long()
       with most of its features.

       #include <stdio.h>

       main (argc, argv)
            int argc;
            char **argv;
         int c;
         int digit_optind = 0;

         while (1)
             int this_option_optind = optind ? optind : 1;
             int option_index = 0;
             static struct option long_options[] =
               {"add", 1, 0, 0},
               {"append", 0, 0, 0},
               {"delete", 1, 0, 0},
               {"verbose", 0, 0, 0},
               {"create", 1, 0, 'c'},
               {"file", 1, 0, 0},
               {0, 0, 0, 0}

             c = getopt_long (argc, argv, "abc:d:012",
                        long_options, &option_index);
             if (c == -1)

             switch (c)
               case 0:
                 printf ("option %s", long_options[option_index].name);
                 if (optarg)
                   printf (" with arg %s", optarg);
                 printf ("\n");

               case '0':
               case '1':
               case '2':
                 if (digit_optind != 0 && digit_optind != this_option_optind)
                   printf ("digits occur in two different argv-elements.\n");
                 digit_optind = this_option_optind;
                 printf ("option %c\n", c);

               case 'a':
                 printf ("option a\n");

               case 'b':
                 printf ("option b\n");

               case 'c':
                 printf ("option c with value `%s'\n", optarg);

               case 'd':
                 printf ("option d with value `%s'\n", optarg);

               case '?':

                 printf ("?? getopt returned character code 0%o ??\n", c);

         if (optind < argc)
             printf ("non-option ARGV-elements: ");
             while (optind < argc)
             printf ("%s ", argv[optind++]);
             printf ("\n");

         exit (0);


       This manpage is confusing.

       The POSIX.2  specification  of  getopt()  has  a  technical  error  described  in  POSIX.2
       Interpretation  150.   The  GNU  implementation  (and  probably all other implementations)
       implements the correct behaviour rather than that specified.


              POSIX.2, provided the environment variable POSIXLY_CORRECT is set.  Otherwise,  the
              elements  of argv aren't really const, because we permute them.  We pretend they're
              const in the prototype to be compatible with other systems.


       <> (revisão)