解释一下这个函数 int _getopt_internal (int argc, char *const *argv, const char *optstring,
const struct option *longopts, int *longind, int long_only)
{
optarg = NULL;
if (optind == 0)
optstring = _getopt_initialize (optstring);
if (nextchar == NULL || *nextchar == '\0')
{
/* Advance to the next ARGV-element. */
if (ordering == PERMUTE)
{
/* If we have just processed some options following some non-options,
exchange them so that the options come first. */
if (first_nonopt != last_nonopt && last_nonopt != optind)
exchange ((char **) argv);
else if (last_nonopt != optind)
first_nonopt = optind;
/* Skip any additional non-options
and extend the range of non-options previously skipped. */
while (optind < argc
&& (argv[optind][0] != '-' || argv[optind][1] == '\0'))
optind++;
last_nonopt = optind;
}
/* The special ARGV-element `--' means premature end of options.
Skip it like a null option,
then exchange with previous non-options as if it were an option,
then skip everything else like a non-option. */
if (optind != argc && !strcmp (argv[optind], "--"))
{
optind++;
if (first_nonopt != last_nonopt && last_nonopt != optind)
exchange ((char **) argv);
else if (first_nonopt == last_nonopt)
first_nonopt = optind;
last_nonopt = argc;
optind = argc;
}
/* If we have done all the ARGV-elements, stop the scan
and back over any non-options that we skipped and permuted. */
if (optind == argc)
{
/* Set the next-arg-index to point at the non-options
that we previously skipped, so the caller will digest them. */
if (first_nonopt != last_nonopt)
optind = first_nonopt;
return EOF;
}
/* If we have come to a non-option and did not permute it,
either stop the scan or describe it to the caller and pass it by. */
if ((argv[optind][0] != '-' || argv[optind][1] == '\0'))
{
if (ordering == REQUIRE_ORDER)
return EOF;
optarg = argv[optind++];
return 1;
}
/* We have found another option-ARGV-element.
Skip the initial punctuation. */
nextchar = (argv[optind] + 1
+ (longopts != NULL && argv[optind][1] == '-'));
}
/* Decode the current option-ARGV-element. */
/* Check whether the ARGV-element is a long option.
If long_only and the ARGV-element has the form "-f", where f is
a valid short option, don't consider it an abbreviated form of
a long option that starts with f. Otherwise there would be no
way to give the -f short option.
On the other hand, if there's a long option "fubar" and
the ARGV-element is "-fu", do consider that an abbreviation of
the long option, just like "--fu", and not "-f" with arg "u".
This distinction seems to be the most useful approach. */
if (longopts != NULL
&& (argv[optind][1] == '-'
|| (long_only && (argv[optind][2] || !my_index (optstring, argv[optind][1])))))
{
char *nameend;
const struct option *p;
const struct option *pfound = NULL;
int exact = 0;
int ambig = 0;
int indfound = 0;
int option_index;
for (nameend = nextchar; *nameend && *nameend != '='; nameend++)
/* Do nothing. */ ;
/* Test all long options for either exact match
or abbreviated matches. */
for (p = longopts, option_index = 0; p->name; p++, option_index++)
if (!strncmp (p->name, nextchar, nameend - nextchar))
{
if (nameend - nextchar == (int) strlen (p->name))
{
/* Exact match found. */
pfound = p;
indfound = option_index;
exact = 1;
break;
}
else if (pfound == NULL)
{
/* First nonexact match found. */
pfound = p;
indfound = option_index;
}
else
/* Second or later nonexact match found. */
ambig = 1;
}
if (ambig && !exact)
{
if (opterr)
fprintf (stderr, "%s: option `%s' is ambiguous\n",
argv[0], argv[optind]);
nextchar += strlen (nextchar);
optind++;
return '?';
}
if (pfound != NULL)
{
option_index = indfound;
optind++;
if (*nameend)
{
/* Don't test has_arg with >, because some C compilers don't
allow it to be used on enums. */
if (pfound->has_arg)
optarg = nameend + 1;
else
{
if (opterr)
{
if (argv[optind - 1][1] == '-')
/* --option */
fprintf (stderr,
"%s: option `--%s' doesn't allow an argument\n",
argv[0], pfound->name);
else
/* +option or -option */
fprintf (stderr,
"%s: option `%c%s' doesn't allow an argument\n",
argv[0], argv[optind - 1][0], pfound->name);
}
nextchar += strlen (nextchar);
return '?';
}
}
else if (pfound->has_arg == 1)
{
if (optind < argc)
optarg = argv[optind++];
else
{
if (opterr)
fprintf (stderr, "%s: option `%s' requires an argument\n",
argv[0], argv[optind - 1]);
nextchar += strlen (nextchar);
return optstring[0] == ':' ? ':' : '?';
}
}
nextchar += strlen (nextchar);
if (longind != NULL)
*longind = option_index;
if (pfound->flag)
{
*(pfound->flag) = pfound->val;
return 0;
}
return pfound->val;
}
/* Can't find it as a long option. If this is not getopt_long_only,
or the option starts with '--' or is not a valid short
option, then it's an error.
Otherwise interpret it as a short option. */
if (!long_only || argv[optind][1] == '-'
|| my_index (optstring, *nextchar) == NULL)
{
if (opterr)
{
if (argv[optind][1] == '-')
/* --option */
fprintf (stderr, "%s: unrecognized option `--%s'\n",
argv[0], nextchar);
else
/* +option or -option */
fprintf (stderr, "%s: unrecognized option `%c%s'\n",
argv[0], argv[optind][0], nextchar);
}
nextchar = (char *) "";
optind++;
return '?';
}
}
/* Look at and handle the next short option-character. */
{
char c = *nextchar++;
char *temp = my_index (optstring, c);
/* Increment `optind' when we start to process its last character. */
if (*nextchar == '\0')
++optind;
if (temp == NULL || c == ':')
{
if (opterr)
{
if (posixly_correct)
/* 1003.2 specifies the format of this message. */
fprintf (stderr, "%s: illegal option -- %c\n", argv[0], c);
else
fprintf (stderr, "%s: invalid option -- %c\n", argv[0], c);
}
optopt = c;
return '?';
}
if (temp[1] == ':')
{
if (temp[2] == ':')
{
/* This is an option that accepts an argument optionally. */
if (*nextchar != '\0')
{
optarg = nextchar;
optind++;
}
else
optarg = NULL;
nextchar = NULL;
}
else
{
/* This is an option that requires an argument. */
if (*nextchar != '\0')
{
optarg = nextchar;
/* If we end this ARGV-element by taking the rest as an arg,
we must advance to the next element now. */
optind++;
}
else if (optind == argc)
{
if (opterr)
{
/* 1003.2 specifies the format of this message. */
fprintf (stderr, "%s: option requires an argument -- %c\n",
argv[0], c);
}
optopt = c;
if (optstring[0] == ':')
c = ':';
else
c = '?';
}
else
/* We already incremented `optind' once;
increment it again when taking next ARGV-elt as argument. */
optarg = argv[optind++];
nextchar = NULL;
}
}
return c;
}
}
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