term% cat index.txt ARG(2) System Calls Manual ARG(2)
NAME
ARGBEGIN, ARGEND, ARGC, ARGF, arginit, argopt - process option letters
from argv
SYNOPSIS
#include <u.h>
#include <libc.h>
ARGBEGIN {
char *ARGF();
Rune ARGC();
} ARGEND
extern char *argv0;
/* Alef only */
Arg *arginit(int argc, byte **argv);
Rune argopt(Arg *arg);
byte *argf(Arg *arg);
DESCRIPTION
These macros assume the names argc and argv are in scope; see exec(2).
ARGBEGIN and ARGEND surround code for processing program options. The
code should be the cases of a C switch on option characters; it is exe‐
cuted once for each option character. Options end after an argument
--, before an argument -, or before an argument that doesn't begin with
-.
ARGC() returns the current option character.
ARGF() returns the current option argument: a pointer to the rest of
the option string if not empty, or the next argument in argv if any, or
0. ARGF must be called just once for each option that takes an argu‐
ment.
After ARGBEGIN, argv0 is a copy of argv[0] (conventionally the name of
the program).
After ARGEND, argv points at a zero-terminated list of the remaining
argc arguments.
Alef
The Alef argument processing routines are unrelated. Instead, an aggr
called Arg is initialized by a call to arginit. Successive calls to
argopt return successive option characters, or zero at the end of the
options. After a call to argopt, argf will return any argument string
associated with the option.
EXAMPLES
This C program can take option b and option f, which requires an argu‐
ment.
#include <u.h>
#include <libc.h>
void
main(int argc, char *argv[])
{
char *f;
print("%s", argv[0]);
ARGBEGIN {
case 'b':
print(" -b");
break;
case 'f':
print(" -f(%s)", (f=ARGF())? f: "no arg");
break;
default:
print(" badflag('%c')", ARGC());
} ARGEND
print(" %d args:", argc);
while(*argv)
print(" '%s'", *argv++);
print("\n");
exits(0);
}
Here is the output for the run prog -bffile1 -r -f file2 arg1 arg2
prog -b -f(file1) badflag('r') -f(file2) 2 args: 'arg1' 'arg2'
This Alef program accepts options b and, with an attached file name, f.
#include <alef.h>
void
main(int argc, byte **argv)
{
int a, ac, bflag;
byte *file;
Arg *arg;
arg = arginit(argc, argv);
while(ac = argopt(arg)) switch(ac){
case 'b':
bflag = 1;
break;
case 'f':
file = argf(arg);
break;
}
for(a=0; a<arg->ac; a++)
print("argument %s\n", arg->av[a]);
}
SOURCE
/sys/include/libc.h
ARG(2)