getopt(3C) (MLX Addendum)          (MLX)          getopt(3C) (MLX Addendum)

NAME
     getopt - get option letter from argument vector (MLX addendum)

SYNOPSIS
     #include <stdio.h>

     int getopt(int argc, char *const *argv, const char *optstring);
     extern char *optarg;
     extern int optind, opterr;

DESCRIPTION
     The function getopt() is a command-line parser. It returns the next
     option letter in argv that matches a letter in optstring.

     The function getopt() places in optind the argv index of the next
     argument to be processed. The external variable optind is initialized
     to 1 before the first call to the function getopt().

     The argument optstring is a string of recognized option letters; if a
     letter is followed by a colon, the option is expected to have an argu-
     ment that may be separated from it by white space.

     The variable optarg is set to point to the start of the option argu-
     ment on return from getopt().

     When all options have been processed (i.e., up to the first non-option
     argument), the function getopt() returns EOF. The special option --
     may be used to delimit the end of the options; EOF will be returned
     and -- will be skipped.

     The following rules comprise the Reliant UNIX standard for command-
     line syntax:

     RULE  1:  Command names must be between two and nine characters.

     RULE  2:  Command names must include lower-case letters and digits
               only.

     RULE  3:  Option names must be a single character in length.

     RULE  4:  All options must be delimited by the - character.

     RULE  5:  Options with no arguments may be grouped behind one delim-
               iter.

     RULE  6:  The first option-argument following an option may be pre-
               ceded by white space.

     RULE  7:  Option arguments cannot be optional.

     RULE  8:  Groups of option arguments following an option must be
               separated by commas or separated by white space and quoted.



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getopt(3C) (MLX Addendum)          (MLX)          getopt(3C) (MLX Addendum)

     RULE  9:  All options must precede operands on the command line.

     RULE 10:  The characters -- may be used to delimit the end of the
               options.

     RULE 11:  The order of options relative to one another should not
               matter.

     RULE 12:  The order of operands may matter and position-related
               interpretations should be determined on a command-specific
               basis.

     RULE 13:  The - character preceded and followed by white space should
               be used only to mean standard input.

RETURN VALUE
     The function getopt() returns a question mark (?) when it encounters
     an option letter not included in optstring; it also prints an error
     message on stderr if opterr is non-zero (opterr is initialized to 1).
     The message is printed in the standard error format. getopt() supports
     localized output messages. If the appropriate translated system mes-
     sages are installed on the system, they are selected by the most
     recent call to setlocale() (using the LC_ALL or LC_MESSAGES
     categories).

     The label defined by a call to setlabel() will be used if available,
     otherwise the name of the utility (argv[0]) will be used.

EXAMPLE
     The following code fragment shows how one might process the options
     and arguments for a command that takes: mutually exclusive options a
     and b, exactly one of which is required; an optional option i which
     takes an option-argument; and at least two arguments.

     main(int argc, char *argv[] /*, char envp[]*/)
               /* envp is unused in this example */
     {
         int             opt, aflg=0, bflg=0, iflg=0, errflg=0, retval ;
         char            *cmdname, *ifile, *ofile ;
         FILE            *infile, *outfile ;
         extern int      optind, opterr, errno ;
         extern char     *optarg ;

         setlabel("UX:example");
         cmdname = argv[0] ;
         opterr = 0 ;    /* inhibit getopt err msg */
         while ( (opt=getopt(argc,argv,"abi:")) != EOF ) {
             switch ( opt ) {
             case 'a' :
                 aflg += 1 ; break ;
             case 'b' :
                 bflg += 1 ; break ;


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getopt(3C) (MLX Addendum)          (MLX)          getopt(3C) (MLX Addendum)

             case 'i' :
                 iflg += 1 ; ifile = optarg ; break ;
             default :   /* includes '?' case */
                 errflg += 1 ; break ;
             }
         }
         if ( errflg>0 || aflg+bflg!=1 || iflg>1 || argc-optind<2 ) {
             usage_err_exit(cmdname) ;
         }

                                (continues)











































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getopt(3C) (MLX Addendum)          (MLX)          getopt(3C) (MLX Addendum)

         if ( iflg == 0 ) {
             infile = stdin ;
         } else if ( (infile=fopen(ifile,"r")) == NULL ) {
             open_err_exit(cmdname,ifile,errno) ;
         }
         for ( ; optind<argc ; optind+=1 ) {
             if ( (outfile=fopen(ofile=argv[optind],"r+")) == NULL ) {
                 open_err_exit(cmdname,ofile,errno) ;
             }
             if ( (retval=do_work(aflg,bflg,infile,outfile)) != 0 ) {
                 work_err_exit(cmdname,ofile,retval) ;
             }
             if ( fclose(outfile) != 0 ) {
                 close_err_exit(cmdname,ofile,errno) ;
             }
         }
         exit(0) ;
     }

SEE ALSO
     pfmt(3C), setlabel(3C).

































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