Thankyou for your continued help.

Below is the contents of the man file you advised... Is it the libc.a file I need to use? Do I replace all the extern code in the code example you gave me with this file?

I am using an older version of Unix (according to the boss) the version info I have is... IBM RS6000 F50 - AIX Version 4.3.3.


-------------------------------------------------------------------------------
Base Operating System and Extensions Technical Reference, Volume 1
-------------------------------------------------------------------------------

getopt Subroutine

Purpose

Returns the next flag letter specified on the command line.

Library

Standard C Library (libc.a)

Syntax

#include <unistd.h>

int getopt (ArgumentC, ArgumentV, OptionString)

int ArgumentC;

char *const ArgumentV [ ];

const char *OptionString;

extern int optind;

extern int optopt;

extern int opterr;

extern char *optarg;

Description

The optind parameter indexes the next element of the ArgumentV parameter to be
processed. It is initialized to 1 and the getopt subroutine updates it after
calling each element of the ArgumentV parameter.

The getopt subroutine returns the next flag letter in the ArgumentV parameter
list that matches a letter in the OptionString parameter. If the flag takes an
argument, the getopt subroutine sets the optarg parameter to point to the
argument as follows:

o If the flag was the last letter in the string pointed to by an element of
the ArgumentV parameter, the optarg parameter contains the next element of
the ArgumentV parameter and the optind parameter is incremented by 2. If the
resulting value of the optind parameter is not less than the ArgumentC
parameter, this indicates a missing flag argument, and the getopt subroutine
returns an error message.
o Otherwise, the optarg parameter points to the string following the flag
letter in that element of the ArgumentV parameter and the optind parameter
is incremented by 1.

Parameters

ArgumentC Specifies the number of parameters passed to the routine.

ArgumentV Specifies the list of parameters passed to the routine.

OptionString Specifies a string of recognized flag letters. If a letter is
followed by a : (colon), the flag is expected to take a parameter that may or
may not be separated from it by white space.

optind Specifies the next element of the ArgumentV array to be processed.

optopt Specifies any erroneous character in the OptionString parameter.

opterr Indicates that an error has occurred when set to a value other than 0.

optarg Points to the next option flag argument.

Return Values

The getopt subroutine returns the next flag letter specified on the command
line. A value of -1 is returned when all command line flags have been parsed.
When the value of the ArgumentV [optind] parameter is null, *ArgumentV [optind]
is not the - (minus) character, or ArgumentV [optind] points to the "-" (minus)
string, the getopt subroutine returns a value of -1 without changing the value.
If ArgumentV [optind] points to the "- -" (double minus) string, the getopt
subroutine returns a value of -1 after incrementing the value of the optind
parameter.

Error Codes

If the getopt subroutine encounters an option character that is not specified by
the OptionString parameter, a ? (question mark) character is returned. If it
detects a missing option argument and the first character of OptionString is a :
(colon), then a : (colon) character is returned. If this subroutine detects a
missing option argument and the first character of OptionString is not a colon,
it returns a ? (question mark). In either case, the getopt subroutine sets the
optopt parameter to the option character that caused the error. If the
application has not set the opterr parameter to 0 and the first character of
OptionString is not a : (colon), the getopt subroutine also prints a diagnostic
message to standard error.

Examples

The following code fragment processes the flags for a command that can take the
mutually exclusive flags a and b, and the flags f and o, both of which require
parameters.
#include <unistd.h> /*Needed for access subroutine constants*/

main (argc, argv)

int argc;

char **argv;

{

int c;

extern int optind;

extern char *optarg;

.

.

.

while ((c = getopt(argc, argv, "abf:")) != EOF)

{

switch (c)

{

case 'a':

if (bflg)

errflg++;

else

aflg++;

break;

case 'b':

if (aflg)

errflg++;

else

bflg++;

break;

case 'f':

ifile = optarg;

break;

case 'o':

ofile = optarg;

break;

case '?':

errflg++;

} /* case */

if (errflg)

{

fprintf(stderr, "usage: . . . ");

exit(2);

}

} /* while */

for ( ; optind < argc; optind++)

{

if (access(argv[optind], R_OK))

{

.

.

.

}

} /* for */

} /* main */

Implementation Specifics

This subroutine is part of Base Operating System (BOS) Runtime.

Related Information

The getopt command.