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NAME
Cgetopt_long - get long options from command line argument list
SYNOPSIS
#include <Cgetopt.h>
int Cgetopt (int argc, char **argv, char *optstring)
int Cgetopt_long (int argc, char **argv, char *optstring, Coptions_t *long_options, int *index)
DESCRIPTION
The Cgetopt function incrementally parses a command line argument list argv and returns the next known
option character. An option character is known if it has been specified in the string of accepted option
characters optstring.
The Cgetopt_long function is similar to Cgetopt but it accepts options in two forms: words and
characters. The Cgetopt_long function provides a superset of the functionality of Cgetopt. The
additional functionality is described in the section CGETOPT_LONG.
The option string optstring may contain the following elements: 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 x taking an argument. It does not
matter to Cgetopt if a following argument has leading white space.
On return from Cgetopt, Coptarg points to an option argument, if it is anticipated, and the variable
Coptind contains the index to the next argv argument for a subsequent call to Cgetopt. The variable
Coptopt saves the last known option character returned by Cgetopt.
The variables Copterr and Coptind are both initialized to 1. The Coptind variable may be set to another
value before a set of calls to Cgetopt in order to skip over more or less argv entries.
In order to use Cgetopt to evaluate multiple sets of arguments, or to evaluate a single set of arguments
multiple times, the variable Coptreset must be set to 1 before the second and each additional set of
calls to Cgetopt and the variable Coptind must be reinitialized.
The Cgetopt function returns -1 when the argument list is exhausted, or a non-recognized option is
encountered. The interpretation of options in the argument list may be cancelled by the option --
(double dash) which causes Cgetopt to signal the end of argument processing and returns -1. When all
options have been processed (i.e., up to the first non-option argument), Cgetopt returns -1. .P
Cgetopt_long can be used in two ways. In the first way, every long option understood by the program has a
coresponding short option, and the option structure is only used to translate from long option to short
options. When used in this fashion, Cgetopt_long behaves identically to Cgetopt. This is good way to add
long option processing to an existing program with the minimum of rewriting.
In the second mechanism, a long option set a flag in the Coptions_t structure passed, or will store a
pointer to the command line argument in the Coptions_t structure passed to it for options that take
arguments. Additionally, the long option's argument may be specified as a single argument with an equal
sign, e.g myprogram --myoption=somevalue
When a long option is processed the call to Cgetopt_long will return 0. For this reason, long option
processing without shortcuts are not backwards compatible with Cgetopt.
It is possible to combine these methods, providing for long options processing with short option
equivalents for some options. Less frequently used options would be processed as long options only.
USAGE OF CGETOPT_LONG
The Cgetopt_long call requires a structure to be initialized describing the long options. The structure
is:
Coptions_t {
char *name;
int has_arg;
int *flag;
int val;
};
The name field should contain the option name without the leading double dash.
The has_arg field should be one of: NO_ARGUMENT if no argument to the option is expected,
REQUIRED_ARGUMENT if an argument to the option is required or OPTIONAL_ARGUMENT if an argument to the
option may be presented.
If flag is non-NULL, then the integer pointed to by it will set to the value in the val field. If the
flag field is NULL, then the val field will be returned. Setting flag to NULL and setting val to the
corresponding short option will make this function act just like Cgetopt.
DIAGNOSTICS
If the Cgetopt function encounters a character not found in the string optstring or detects a missing
option argument it writes an error message to stderr and returns ?. Setting Copterr 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 reasonable but reduces the amount of error
checking possible.
CGETOPT_LONG EXTENSIONS
The Coptreset variable was added to make it possible to call the Cgetopt function multiple times. This
is an extension to the -p1003.2 specification.
EXAMPLE
#include <Cgetopt.h>
int bflag, ch, fd;
Coptind = 1; /* Required */
Copterr = 1; /* Some stderr output if you want */
bflag = 0;
while ((ch = Cgetopt(argc, argv, "bf:")) != -1)
switch(ch) {
case 'b':
bflag = 1;
break;
case 'f':
if ((fd = open(Coptarg, O_RDONLY, 0)) < 0) {
(void)fprintf(stderr,
"myname: %s: %s\n", Coptarg, strerror(errno));
exit(1);
}
break;
case '?':
default:
usage();
}
argc -= Coptind;
argv += Coptind;
LONG EXAMPLE
#include <Cgetopt.h>
int bflag, ch, fd;
int daggerset;
/* options descriptor */
Coptions_t longopts[] =
{
{"buffy", NO_ARGUMENT, NULL, 'b'},
{"floride", REQUIRED_ARGUMENT, NULL, 'f'},
{"daggerset", NO_ARGUMENT, &daggerset, 1},
{NULL, 0, NULL, 0}
};
Coptind = 1; /* Required */
Copterr = 1; /* Some stderr output if you want */
bflag = 0;
while ((ch = Cgetopt_long(argc, argv, "bf:", longopts, NULL)) != -1)
switch(ch) {
case 'b':
bflag = 1;
break;
case 'f':
if ((fd = open(Coptarg, O_RDONLY, 0)) < 0) {
(void)fprintf(stderr,
"myname: %s: %s\n", Coptarg, strerror(errno));
exit(1);
}
break;
case 0:
if(daggerset) {
fprintf(stderr,"Buffy will put use her dagger"
"to apply floride to dracula's teeth");
}
break;
case '?':
default:
usage();
}
argc -= Coptind;
argv += Coptind;
HISTORY
The Cgetopt function appeared in BSD 4.3. The Cgetopt_long function first appeared in GNU library. This
implementation was imported to NetBSD from a Kerberos distribution.
BUGS
The Cgetopt function was once specified to return EOF instead of -1. This was changed by -p1003.2-92 to
decouple Cgetopt from <stdio.h>.
A single dash - may be specified as an character in optstring, however it should never have an argument
associated with it. This allows Cgetopt 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 provided for backward
compatibility only. By default, a single dash causes Cgetopt to return -1. This is, we believe,
compatible with System V.
It is also possible to handle digits as option letters. This allows Cgetopt 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 provided for backward compatibility only. The following code fragment works in most
cases.
int length;
char *p;
Coptind = 1; /* Required */
Copterr = 1; /* Some stderr output if you want */
while ((c = Cgetopt(argc, argv, "0123456789")) != -1)
switch (c) {
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
p = argv[Coptind - 1];
if (p[0] == '-' && p[1] == ch && !p[2])
length = atoi(++p);
else
length = atoi(argv[Coptind] + 1);
break;
}
}
The OPTIONAL_ARGUMENT always eats the following argument unless the argument is included via the
--option=argument notation.
AUTHOR
Copyright (c) 1988, 1991, 1993 The Regents of the University of California. All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided
that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
the following disclaimer in the documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software must display the following
acknowledgement: This product includes software developed by the University of California, Berkeley and
its contributors.
4. Neither the name of the University nor the names of its contributors may be used to endorse or promote
products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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