TH GETFLAGS 9.2
SH NAME
getflags, usage \- process flag arguments in argv
SH SYNOPSIS
nf
B
#include <libg.h>
PP
B
#include <fb.h>
PP
B
int getflags(int argc, char *argv[], char *flags)
PP
B
int usage(char *tail)
PP
B
extern char **flag[], cmdline[], *cmdname, *flagset[];
fi
SH DESCRIPTION
I Getflags
digests an argument vector
IR argv ,
finding flag arguments listed in
IR flags .
I Flags
is a string of flag letters.
A letter followed by a colon and a number
is expected to have the given number of parameters.
A flag argument starts with
RB ` - '
and is followed by any number of flag letters.
A flag with one or more parameters must be the last flag in an argument.
If any characters follow it, they are the flag's first parameter. Otherwise
the following argument is the first parameter. Subsequent parameters are taken
from subsequent arguments.
PP
The global array
I flag
is set to point to an array of parameters for each flag found.
Thus, if flag
B -x
was seen,
B flag['x']
is non-zero, and
B flag['x'][i]
is the flag's
IR i th
parameter.
If flag
B -x
has no parameters
BR flag['x']==flagset .
Flags not found
are marked with a zero.
Flags and their parameters are deleted from
IR argv .
I Getflags
returns the adjusted argument count.
PP
I Getflags
stops scanning for flags upon encountering a non-flag argument,
or the argument
BR -- ,
which is deleted.
PP
I Getflags
places a pointer to
IB argv [0]
in the external variable
IR cmdname .
It also concatenates the original members of
IR argv ,
separated by spaces, and places the result in the external array
IR cmdline .
PP
I Usage
constructs a usage message, prints it on the standard error file,
and exits with status 1.
The command name printed is
IB argv [0]\f1.
Appropriate flag usage syntax is generated from
IR flags .
As an aid,
explanatory information about flag parameters may be included in
I flags
in square brackets as in the example.
I Tail
is printed at the end of the message.
If
I getflags
encountered an error,
I usage
tries to indicate the cause.
SH EXAMPLES
EX
main(int argc, char *argv[]){
if((argc=getflags(argc, argv, "vinclbhse:1[expr]", 1))==-1)
usage("[file ...]");
}
EE
might print:
EX
Illegal flag -u
Usage: grep [-vinclbhs] [-e expr] [file ...]
EE
SH SOURCE
B /sys/src/libfb/getflags.c
SH "SEE ALSO"
IR ARG (2)
SH DIAGNOSTICS
I Getflags
returns \-1 on error:
a syntax error in
IR flags ,
setting a flag more than once, setting a flag not mentioned
in
IR flags ,
or running out of arguments while collecting a flag's parameters.
