getopt_long用法及实例

GETOPT(3)                  Linux Programmer?. Manual                 GETOPT(3)


NAME

       getopt - Parse command-line options

       翻译:getopt 解析命令行参数

SYNOPSIS
       #include <unistd.h>            ----------包含头文件

       int getopt(int argc, char * const argv[],  -------------------main函数两个入参

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[], -------------------------------main函数两个入参
                  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);


DESCRIPTION

       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.  

翻译:getopt函数解析命令行选项，argc入参是选项的个数，argv是命令行选项的排列，是从main函数传递进来的。

An element of argv that starts with ?.?.(and is not exactly "-" or "--") is an option element.  

argv的起始元素是?? 是一个选项元素

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.

翻译：如果重复调用getopt()函数，会为每个选项元素的选项字符返回成功

       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.
若没有更多的选项getopt函数返回-1，

       optstring is a string containing the legitimate option characters. optsting参数是包含了合法的选项字符。

 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  fol-
       lowed  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.


       If getopt() finds an option character in argv that was not included in optstring, or if it detects a missing option argument, it returns ?.?. and sets the external
       variable optopt to the actual option character.  If the first character (following any optional ?.?.r ?.?.described above) of optstring  is  a  colon  (?.?.,  then
       getopt()  returns ?.?.instead of ?.?.to indicate a missing option argument.  If an error was detected, and the first character of optstring is not a colon, and the
       external variable opterr is non-zero (which is the default), getopt() prints an error message.


       The getopt_long() function works like getopt() except that it also accepts long options, started out by two dashes.  (If the program  accepts  only  long  options,
       then optstring should be specified as an empty string (""), not NULL.)  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.


       has_arg
              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?. match a long
       option, but does match a short option, it is parsed as a short option instead.


RETURN VALUE
       If an option was successfully found, then getopt() returns the option character.  If all command-line options have been  parsed,  then  getopt()  returns  -1.   If
       getopt() encounters an option character that was not in optstring, then ?.?.is returned.  If getopt() encounters an option with a missing argument, then the return
       value depends on the first character in optstring: if it is ?.?. then ?.?.is returned; otherwise ?.?.is returned.


       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.


ENVIRONMENT VARIABLES
       POSIXLY_CORRECT
              If this is set, then option processing stops as soon as a non-option argument is encountered.


       _<PID>_GNU_nonoption_argv_flags_
              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.


EXAMPLE
       The following example program illustrates the use of getopt_long() with most of its features.


       #include <stdio.h>     /* for printf */
       #include <stdlib.h>    /* for exit */
       #include <getopt.h>


       int
       main (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, ?.?.,
                   {"file", 1, 0, 0},
                   {0, 0, 0, 0}
               };


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


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


               case ?.?.
               case ?.?.
               case ?.?.
                   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);
                   break;


               case ?.?.
                   printf ("option a\n");
                   break;


               case ?.?.
                   printf ("option b\n");
                   break;


               case ?.?.
                   printf ("option c with value ?.s?.n", optarg);
                   break;


               case ?.?.
                   printf ("option d with value ?.s?.n", optarg);
                   break;


               case ?.?.
                   break;


               default:
                   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);
       }


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


CONFORMING TO
       getopt():
              POSIX.2 and POSIX.1-2001, provided the environment variable POSIXLY_CORRECT is set.  Otherwise, the elements of argv aren?. really const, because we permute
              them.  We pretend they?.e const in the prototype to be compatible with other systems.


              On some older implementations, getopt() was declared in  <stdio.h>.   SUSv1  permitted  the  declaration  to  appear  in  either  <unistd.h>  or  <stdio.h>.
              POSIX.1-2001 marked the use of <stdio.h> for this purpose as LEGACY.  POSIX.1-2001 does not allow the declaration to appear in <stdio.h>.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>


#define SOFTWARE_NAME "NAME"
#define VERSION "1.01"


static const char *optstring = "hv";


static struct option longopts[] = {
{"help", no_argument, NULL, 'h'},
{"version", no_argument, NULL, 'v'},
{0, 0, 0, 0}
};


void print_option_help(void)
{
    static const char *help =
        "Usage: getopt_long [OPTIONS]\n"
        "Options are:\n"
" -h, --help      Display this help text and exit\n"
        " -v, --version    Get software version\n";
    printf("%s", help);
}


int parse_cmd_line(int argc, char *const argv[])
{
int option;

    while ((option = getopt_long(argc, argv, optstring, longopts, NULL)) != -1)
{
        switch (option) {
case 'h':
print_option_help();
break;
        case 'v':
            printf("JLKJK %s.%sR\n", SOFTWARE_NAME, VERSION);
            break;
        case '?':
            return -1;
        }
}

return 0;
}


int main(int argc, char **argv)
{
    if (parse_cmd_line(argc, argv) < 0) { // parse command line.
        exit(-1);
    }

return 0;
}