ARG(2) ARG(2)
NAME
ARG - process option letters from argv
SYNOPSIS
#include <libc.h>
ARGBEGIN {
} ARGEND
char *ARGF();
char ARGC();
extern char *argv0;
DESCRIPTION
Command-line arguments to programs (see exec(2)) are conven-
tionally arranged as a set of options - strings beginning
with a - (minus sign) - followed by plain arguments such as
file names. The ARG macros provide a convenient means for
processing these options. Option characters appear in
nonempty clusters preceded by -. After options processing
is terminated (by an argument not starting with -, or by the
argument -- which is then skipped, or by the argument -),
execution resumes after the ARGEND.
The body of a switch statement should be put between
ARGBEGIN{ and }ARGEND; it is executed once for each option
character (the character itself may be referenced by
ARGC()). If an option takes a string argument (that is, the
rest of the current option string or if that is empty, the
next argument), it can be referenced by ARGF(). After
ARGEND, argv points at a zero-terminated list of the remain-
ing argc arguments.
ARGBEGIN also sets up argv0 to point at argv[0] (convention-
ally the name of the program).
EXAMPLES
This program processes arguments for a command that can take
option b and option f, which requires an argument.
#include <u.h>
#include <libc.h>
main(int argc, char *argv[])
{
char *f;
print("%s", argv[0]);
ARGBEGIN{
case 'b': print(" -b"); break;
case 'f': f = ARGF(); print(" -f(%s)", f?f:"no arg"); break;
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ARG(2) ARG(2)
default: print(" badflag('%c')", ARGC()); break;
}ARGEND
print(" %d args:", argc);
while(*argv)
print(" '%s'", *argv++);
print("\n");
exits(0);
}
When this program is run as
prog -bffile1 -r -f file2 arg1 argn
it yields
prog -b -f(file1) badflag('r') -f(file2) 2 args: 'arg1' 'argn'
DIAGNOSTICS
ARGF() returns 0 on error.
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