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NAME    [Toc]    [Back]

     getopt_long, getopt_long_only - get long options  from  command line argument

SYNOPSIS    [Toc]    [Back]

     #include <getopt.h>

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

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

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

DESCRIPTION    [Toc]    [Back]

     The  getopt_long()  function  is similar to getopt(3) but it
accepts options
     in two forms: words and characters.  The getopt_long() function provides
     a superset of the functionality of getopt(3).  getopt_long()
can be used
     in two ways.  In the first way, every long option understood
by the program
 has a corresponding short option, and the option structure is only
     used to translate from long options to short options.   When
used in this
     fashion,  getopt_long()  behaves  identically  to getopt(3).
This is a good
     way to add long option processing  to  an  existing  program
with the minimum
     of rewriting.

     In  the  second  mechanism, a long option sets a flag in the
option structure
 passed, or will store a pointer to the command line argument in the
     option  structure  passed  to it for options that take arguments.  Additionally,
 the long option's argument may be specified as a  single argument
     with an equal sign, e.g.

     myprogram --myoption=somevalue

     When  a  long  option is processed the call to getopt_long()
will return 0.
     For this reason, long option processing without shortcuts is
not backwards
 compatible with getopt(3).

     It  is possible to combine these methods, providing for long
options processing
 with short  option  equivalents  for  some  options.
Less frequently
     used options would be processed as long options only.

     The  getopt_long()  call requires a structure to be initialized describing
     the long options.  The structure is:

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

     The name field should contain the option  name  without  the
leading double

     The has_arg field should be one of:

     no_argument        no argument to the option is expect.

     required_argument  an argument to the option is required.

     optional_argument  an argument to the option may be presented.

     If flag is not NULL, then the integer pointed to by it  will
be set to the
     value in the val field.  If the flag field is NULL, then the
val field
     will be returned.  Setting flag to NULL and setting  val  to
the corresponding
  short option will make this function act just like

     If the longindex field is not NULL, then the integer pointed
to by it
     will  be  set  to  the  index of the long option relative to

     The last element of the longopts array has to be filled with

     The   getopt_long_only()  function  behaves  identically  to
getopt_long() with
     the exception that long options may start with `-' in  addition to `--'.
     If  an option starting with `-' does not match a long option
but does
     match a single-character option, the single-character option
is returned.

RETURN VALUES    [Toc]    [Back]

     If  the  flag  field in struct option is NULL, getopt_long()
     getopt_long_only() return the value  specified  in  the  val
field, which is
     usually just the corresponding short option.  If flag is not
NULL, these
     functions return 0 and store val in the location pointed  to
by flag.
     These functions return `:' if there was a missing option argument, `?' if
     the user specified an unknown or ambiguous  option,  and  -1
when the argument
 list has been exhausted.

EXAMPLES    [Toc]    [Back]

     int bflag, ch, fd;
     int daggerset;

     /* options descriptor */
     static struct option longopts[] = {
             {    "buffy",        no_argument,              NULL,
'b' },
             {   "fluoride",     required_argument,         NULL,
'f' },
             {  "daggerset",  no_argument,            &daggerset,
1 },
             {   NULL,           0,                         NULL,
0 }

     bflag = 0;
     while ((ch = getopt_long(argc, argv, "bf:", longopts, NULL))
!= -1)
             switch (ch) {
             case 'b':
                     bflag = 1;
             case 'f':
                     if ((fd = open(optarg, O_RDONLY, 0)) == -1)
                             err(1, "unable to open %s", optarg);
             case 0:
                     if (daggerset) {
                             fprintf(stderr,"Buffy  will  use her
dagger to "
                                 "apply  fluoride  to   dracula's
     argc -= optind;
     argv += optind;


     This section describes differences to the GNU implementation
found in

     o    handling of - as first char of option string  in  presence of environment

          GNU       ignores  POSIXLY_CORRECT  and returns non-options as arguments
 to option '1'.

          OpenBSD  honors POSIXLY_CORRECT and stops at the  first

     o     handling  of - within the option string (not the first

          GNU      treats a `-' on the command line as a  non-argument.

          OpenBSD   a  `-' within the option string matches a `-'
(single dash)
                   on the command line.   This  functionality  is
provided for
                   backward  compatibility with programs, such as
su(1), that
                   use `-' as an option flag.  This  practice  is
wrong, and
                   should not be used in any current development.

     o    handling of :: in options string in presence of  POSIXLY_CORRECT:

          Both      GNU  and  OpenBSD ignore POSIXLY_CORRECT here
and take :: to
                   mean the preceding option  takes  an  optional

     o    return value in case of missing argument if first character (after +
          or -) in option string is not ':':

          GNU      returns '?'

          OpenBSD  returns ':' (since OpenBSD's getopt does).

     o    handling of --a in getopt:

          GNU      parses this as option '-', option 'a'.

          OpenBSD  parses this as '--', and returns -1  (ignoring
the a).  (Because
 the original getopt does.)

     o    setting of optopt for long options with flag != NULL:

          GNU      sets optopt to val.

          OpenBSD  sets optopt to 0 (since val would never be returned).

     o    handling of -W with W; in option string in getopt  (not

          GNU      causes a segfault.

          OpenBSD   no special handling is done; ``W;'' is interpreted as two
                   separate options, neither of which take an argument.

     o     setting of optarg for long options without an argument
that are invoked
 via -W (W; in option string):

          GNU      sets optarg to the option name  (the  argument
of -W).

          OpenBSD   sets optarg to NULL (the argument of the long

     o    handling of -W with an argument that is not  (a  prefix
to) a known
          long option (W; in option string):

          GNU       returns -W with optarg set to the unknown option.

          OpenBSD  treats this as an error (unknown  option)  and
returns '?'
                   with  optopt  set  to 0 and optarg set to NULL
(as GNU's man
                   page documents).

     o    The error messages are different.

     o    OpenBSD does not permute the  argument  vector  at  the
same points in
          the calling sequence as GNU does.  The aspects normally
used by the
          caller (ordering after -1 is returned, value of  optind
relative to
          current  positions) are the same, though.  (We do fewer

ENVIRONMENT    [Toc]    [Back]

     POSIXLY_CORRECT  If set, option processing  stops  when  the
first non-option
  is  found and a leading `-' or `+' in
the optstring
                      is ignored.

SEE ALSO    [Toc]    [Back]


HISTORY    [Toc]    [Back]

     The getopt_long() and getopt_long_only() functions first appeared in GNU
     libiberty.   This  implementation  first appeared in OpenBSD

BUGS    [Toc]    [Back]

     The argv argument is not really const as its elements may be
     (unless POSIXLY_CORRECT is set).

OpenBSD      3.6                           April      1,     2000
[ Back ]
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