getopt.3

.TH getopt 3
.SH NAME
getopt \- get option character from command line
.SH SYNTAX
.B #include <getopt.h>

char *\fBoptarg\fP;
.br
int \fBoptind\fP;
.br
int \fBoptpos\fP;
.br
int \fBopteof\fP;
.br
int \fBoptproblem\fP;
.br
char *\fBoptprogname\fP;
.br
int \fBopterr\fP;

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

int \fIargc\fR;
.br
char **\fIargv\fR;
.br
char *\fIopts\fR;
.SH DESCRIPTION
This is a clone version of
the standard
.B getopt
library,
built on top of
.BR subgetopt(3) .

See
.B subgetopt(3)
for a detailed description of
.B getopt
processing.
The main difference between
.B getopt
and
.B subgetopt
is that
.B getopt
prints error messages
in case of problems.
To turn off these error messages, set
.B opterr
(default nonzero)
to zero.

This clone version of
.B getopt
also provides an
.B optprogname
variable.
There are two uses for this variable:

(1)
By default
.B optprogname
is null.
When
.B getopt
sees this,
it
attempts to initialize
.B optprogname
from
.IR argv\fB[0] ,
stripping the directory name.
The calling program can use
.B optprogname
after calling
.B getopt
at least once.
This is appropriate if the name of the program should be
determined from its command line.

(2)
.B getopt
prints
.B optprogname
at the beginning
of any error messages.
So the calling program can,
before calling
.BR getopt ,
initialize
.B optprogname
as desired.
This is appropriate if the name of the program should not be
determined from its command line.
.SH "COMPATIBILITY"
Old versions of
.B getopt
do not include
.BR opterr .
.BR optpos ,
.BR opteof ,
.BR optproblem ,
and
.B optprogname
are specific to this clone version of
.BR getopt .

Many features of this clone version of
.B getopt
are poorly defined, if available at all,
in most versions of
.BR getopt .
For example, the standard
.B getopt
interface does not define
.B optind
until the end of the option list.
And
.B optarg
is not defined
unless
.B getopt
has just returned
an option which takes an argument.
In this clone version,
.B optind
and
.B optpos
always indicate the next character to be read,
and
.B optarg
is null whenever
the current option does not take an argument.
See
.B subgetopt(3)
for precise definitions of the parsing procedure.

When it reaches the end of the option list,
this version of
.B getopt
always returns
.BR opteof ,
which is the same as
.BR subgetoptdone ,
which is initialized to
.BR SUBGETOPTDONE ,
which is defined as \-1.
The standard behavior is to return
EOF
from
.B stdio(3).
This is incompatible
on any weird machine where
EOF is different from \-1.
The calling program could set
.B opteof
to EOF to imitate the standard behavior.

Like most versions of
.BR getopt ,
this clone version allows, but does not demand, that
option arguments be
separated from the option by whitespace, i.e., be
in the next command-line argument.

Some versions of
.B getopt
provide an
.B optopt
variable.
.B optopt
is incompatible across systems:
for example,
GNU
.B getopt
uses it the same way that this clone version uses
.BR optproblem ,
while
BSD
.B getopt
uses it to
indicate the last option character returned by
.BR getopt .
This clone version does not provide
.BR optopt .
The use of
.B optopt
is strongly discouraged.

Some versions of
.B getopt
do not recognize a double hyphen as the end of arguments.
This version allows a double hyphen, or in fact any argument beginning
with two hyphens.

A lone hyphen is always recognized as the end of arguments.
Some versions of
.B getopt
allow lone hyphens as options.
This practice is wrong and is strongly discouraged.
.SH "SYNTAX NOTE"
.B getopt
is actually a macro abbreviation for
.BR getoptmine .
The external
.B opterr
and
.B optprogname
variables
are macros for
.B getopterr
and
.BR getoptprogname .
All the other
.B opt
variables are macros
for
.BR subgetopt .
These macros are defined in
.BR <getopt.h> ,
unless
.B GETOPTNOSHORT
is defined.
Further macros are defined in
.BR <subgetopt.h> ,
which is included by
.BR <getopt.h> ,
unless
.B SUBGETOPTNOSHORT
is defined.
.SH VERSION
getopt version 1.9, 931129.
.SH AUTHOR
Placed into the public domain by Daniel J. Bernstein.