# 2.11BSD#431 - /usr/man/cat3/getopt.0

    GETOPT(3)	    UNIX Programmer's Manual		GETOPT(3)

    NAME
         getopt - get option character from command line argument
         list

    SYNOPSIS
         #include <stdlib.h>

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

         int
         getopt(argc, argv, optstring)
         int argc;
         char **argv;
         char *optstring;

    DESCRIPTION
         The getopt() function incrementally parses a command line
         argument list argv and returns the next known option charac-
         ter.  An option character is known if it has been specified
         in the string of accepted option characters, optstring.

         The option string optstring may contain the following ele-
         ments: individual characters, and characters followed by a
         colon to indicate an option argument is to follow.  For
         example, an option string """x"" recognizes an option
         ``-x'', and an option string """x:"" recognizes an option
         and argument ``-x argument''.  It does not matter to
         getopt() if a following argument has leading white space.

         On return from getopt(), optarg points to an option argu-
         ment, if it is anticipated, and the variable optind contains
         the index to the next argv argument for a subsequent call to
         getopt().	The variable optopt saves the last known option
         character returned by getopt().

         The variable opterr and optind are both initialized to 1.
         The optind variable may be set to another value before a set
         of calls to getopt() in order to skip over more or less argv
         entries.

         In order to use getopt() to evaluate multiple sets of argu-
         ments, or to evaluate a single set of arguments multiple
         times, the variable optreset must be set to 1 before the
         second and each additional set of calls to getopt(), and the
         variable optind must be reinitialized.

         The getopt() function returns an EOF when the argument list
         is exhausted, or a non-recognized option is encountered.

    Printed 11/26/99	January 12, 1996			1

    GETOPT(3)	    UNIX Programmer's Manual		GETOPT(3)

         The interpretation of options in the argument list may be
         cancelled by the option `--' (double dash) which causes
         getopt() to signal the end of argument processing and return
         an EOF.  When all options have been processed (i.e., up to
         the first non-option argument), getopt() returns EOF.

    DIAGNOSTICS
         If the getopt() function encounters a character not found in
         the string optarg or detects a missing option argument it
         writes an error message and returns `?' to the stderr.  Set-
         ting opterr to a zero will disable these error messages.  If
         optstring has a leading `:' then a missing option argument
         causes a `:' to be returned in addition to suppressing any
         error messages.

         Option arguments are allowed to begin with `-'; this is rea-
         sonable but reduces the amount of error checking possible.

    EXTENSIONS
         The optreset variable was added to make it possible to call
         the getopt() function multiple times.  This is an extension
         to the IEEE Std1003.2 (``POSIX'') specification.

    EXAMPLE
         extern char *optarg;
         extern int optind;
         int bflag, ch, fd;

         bflag = 0;
         while ((ch = getopt(argc, argv, "bf:")) != EOF)
    	  switch(ch) {
    	  case 'b':
    	       bflag = 1;
    	       break;
    	  case 'f':
    	       if ((fd = open(optarg, O_RDONLY, 0)) < 0) {
    		    (void)fprintf(stderr,
    			"myname: %s: %s\n", optarg, strerror(errno));
    		    exit(1);
    	       }
    	       break;
    	  case '?':
    	  default:
    	       usage();
         }
         argc -= optind;
         argv += optind;

    HISTORY
         The getopt() function appeared 4.3BSD.

    Printed 11/26/99	January 12, 1996			2

    GETOPT(3)	    UNIX Programmer's Manual		GETOPT(3)

    BUGS
         A single dash ``-'' may be specified as an character in opt-
         string , however it should never have an argument associated
         with it.  This allows getopt() to be used with programs that
         expect ``-'' as an option flag.  This practice is wrong, and
         should not be used in any current development.  It is pro-
         vided for backward compatibility only . By default, a single
         dash causes getopt() to return EOF.  This is, we believe,
         compatible with System V.

         It is also possible to handle digits as option letters.
         This allows getopt() to be used with programs that expect a
         number (``-3'') as an option.  This practice is wrong, and
         should not be used in any current development.  It is pro-
         vided for backward compatibility only.  The following code
         fragment works in most cases.

         int length;
         char *p;

         while ((c = getopt(argc, argv, "0123456789")) != EOF)
    	  switch (c) {
    	  case '0': case '1': case '2': case '3': case '4':
    	  case '5': case '6': case '7': case '8': case '9':
    	       p = argv[optind - 1];
    	       if (p[0] == '-' && p[1] == ch && !p[2])
    		    length = atoi(++p);
    	       else
    		    length = atoi(argv[optind] + 1);
    	       break;
    	  }
         }

    Printed 11/26/99	January 12, 1996			3

Generated: 2016-12-26 | Generated by man2html V0.25 page hit count: 296 |