.TH subgetopt 3

.SH NAME

subgetopt \- get option character from command line

.SH SYNTAX

.B #include <subgetopt.h>

char *\fBsgoptarg\fP;

.br

int \fBsgoptind\fP;

.br

int \fBsgoptpos\fP;

.br

int \fBsgoptdone\fP;

.br

int \fBsgoptproblem\fP;

int \fBsgopt(\fP\fIargc,argv,opts\fR\fB)\fP;

int \fIargc\fR;

.br

char **\fIargv\fR;

.br

char *\fIopts\fR;

.SH DESCRIPTION

.B sgopt

returns the next valid command-line option character

from

.IR argv .

Valid option characters are listed in the

.I opts

string.

.I opts

may be empty.

A character in

.I opts

may be followed by a colon,

in which case it

takes an

.I option argument\fR.

Avoid using the characters ?, :, and \- as option characters.

Below

.I option argument

is abbreviated

as

.I optarg

and

.I command-line argument

is abbreviated as

.IR cmdarg .

Options are listed in cmdargs which begin with

a minus sign.

Several options which do not take optargs may be combined

into one cmdarg.

An option which takes an optarg may be handled in two ways.

If it appears at the very end of a cmdarg,

then the entire next cmdarg is the optarg.

But if there are any characters in the cmdarg

after the option character,

then those characters form the optarg.

The optarg is returned in

.BR sgoptarg .

Next time

.B sgopt

looks at the cmdarg which follows the optarg.

If a cmdarg does not begin with a hyphen,

or if it is a lone hyphen not followed by any characters,

or if it begins with two hyphens,

then it terminates option processing,

and

.B sgopt

returns an appropriate code.

If there are two hyphens,

.B sgopt

will advance attention to the next cmdarg,

so it can be called again to read further options.

.SH "PROPER USAGE"

.B sgoptproblem

should be used only when

.B sgopt

returns ?.

.B sgoptind

and

.B sgoptpos

are defined all the time.

.B sgoptarg

is defined all the time;

it is null unless

.B sgopt

has just returned an option with optarg.

.B sgopt

is typically used as follows.

.EX

#include <subgetopt.h>

main(argc,argv) int argc; char **argv; { int opt;

while ((opt = sgopt(argc,argv,"a:s")) != sgoptdone)

.br

  switch(opt) {

.br

    case 'a':

.br

      printf("opt a with optarg %s\\n",sgoptarg); break;

.br

    case 's':

.br

      printf("opt s with no optarg\\n"); break;

.br

    case '?':

.br

      if (argv[sgoptind] && (sgoptind < argc))

.br

        printf("illegal opt %c\\n",sgoptproblem);

.br

      else

.br

        printf("missing arg, opt %c\\n",sgoptproblem);

.br

      exit(1);

.br

  }

argv += sgoptind;

.br

while (*argv) printf("argument %s\\n",*argv++);

.br

exit(0);

.br

}

.EE

The end of the command line is

marked by either

.IR argc ,

or a null pointer in

.IR argv ,

whichever comes first.

Normally

these two markers coincide,

so it is redundant

to test for

both

.I argv\fB[sgoptind]

and

.B sgoptind < \fIargc\fR.

The above code shows both tests as an illustration.

.B Multiple option sets:

One useful technique is to call

.B sgopt

with a primary

.I opts

until it returns EOF,

then call

.B sgopt

with a secondary

.I opts

until it returns EOF.

The user can provide primary options, then a double hyphen,

and then secondary options.

No special handling is needed if some or all of the options are

omitted.

The same technique can be used for any number of option sets

in series.

.B Multiple command lines:

Before parsing a new

.BR argv ,

make sure to

set

.B sgoptind

and

.B sgoptpos

back to

1 and 0.

.SH "PARSING STAGES"

.B sgopt

keeps track of its position in

.I argv

with

.B sgoptind

and

.BR sgoptpos ,

which are initialized to 1 and 0.

It looks at

.I argv\fB[sgoptind][sgoptpos]

and following characters.

.B sgopt

indicates

that no more options are available by

returning

.BR sgoptdone ,

which is initialized to

.BR SUBGETOPTDONE ,

which is defined as \-1.

.B sgopt

begins by setting

.B optarg

to null.

.B Ending conditions:

If

.I argv

is null, or

.B sgoptind

is larger than

.IR argc ,

or the current cmdarg

.I argv\fB[sgoptind]

is null,

then

.B sgopt

returns

.BR optdone .

.B Stage one:

If the current character

is zero,

.B sgopt

moves to the beginning of the next cmdarg.

It then checks the ending conditions again.

.B Stage two:

If

the current position is the begining of the cmdarg,

.B sgopt

checks whether

the current character

is a minus sign.

If not it returns

.BR optdone .

It then

moves

to the next character.

If that character is zero,

.B sgopt

moves

back to the beginning of the cmdarg,

and returns

.BR sgoptdone .

If the character is a minus sign,

.B sgopt

moves to the beginning of the next cmdarg,

and returns

.BR sgoptdone .

.B Stage three:

.B sgopt

records the current character,

.IR c ,

and moves to the next character.

There are three possibilities:

(1)

.I c

is an option character without optarg in

.IR opts ,

or

(2)

.I c

is an option character with optarg in

.IR opts ,

or

(3)

.I c

does not appear in

.IR opts .

(1)

If

.I c

appears as an option character without optarg in

.IR opts ,

.B sgopt

returns

.IR c .

(2)

If

.I c

appears as an option character with optarg in

.IR opts ,

.B sgopt

sets

.B sgoptarg

to the current position,

and moves to the next cmdarg.

If

.B sgoptarg

is nonempty,

.B sgopt

returns

.IR c .

Then

.B sgopt

sets

.B sgoptarg

to

the current cmdarg.

If

the current cmdarg is null,

or past

.IR argc ,

.B sgopt

sets

.B sgoptproblem

to

.I c

and returns ?.

Otherwise

.B sgopt

moves to the next

argument

and returns

.IR c .

(2)

If

.I c

does not appear in

.IR opts ,

.B sgopt

sets

.B sgoptproblem

to

.I c

and returns ?.

.SH "SYNTAX NOTE"

.B sgopt

is actually a macro abbreviation for

.BR subgetopt .

The external

.B sg

variables are also macros

for

.BR subget .

These macros are defined in

.BR <subgetopt.h> ,

unless

.B SUBGETOPTNOSHORT

is defined

when

.B <subgetopt.h>

is included.

.SH VERSION

subgetopt version 0.9, 931129.

.SH AUTHOR

Placed into the public domain by Daniel J. Bernstein.