Reputation: 1437
So I'm in Linux and I want to have a program accept arguments when you execute it from the command line.
For example,
./myprogram 42 -b -s
So then the program would store that number 42 as an int and execute certain parts of code depending on what arguments it gets like -b or -s.
Upvotes: 38
Views: 158153
Reputation: 828090
You could use getopt.
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main (int argc, char **argv)
{
int bflag = 0;
int sflag = 0;
int index;
int c;
opterr = 0;
while ((c = getopt (argc, argv, "bs")) != -1)
switch (c)
{
case 'b':
bflag = 1;
break;
case 's':
sflag = 1;
break;
case '?':
if (isprint (optopt))
fprintf (stderr, "Unknown option `-%c'.\n", optopt);
else
fprintf (stderr,
"Unknown option character `\\x%x'.\n",
optopt);
return 1;
default:
abort ();
}
printf ("bflag = %d, sflag = %d\n", bflag, sflag);
for (index = optind; index < argc; index++)
printf ("Non-option argument %s\n", argv[index]);
return 0;
}
Upvotes: 43
Reputation: 414875
Consider using getopt_long()
. It allows both short and long options in any combination.
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
/* Flag set by `--verbose'. */
static int verbose_flag;
int
main (int argc, char *argv[])
{
while (1)
{
static struct option long_options[] =
{
/* This option set a flag. */
{"verbose", no_argument, &verbose_flag, 1},
/* These options don't set a flag.
We distinguish them by their indices. */
{"blip", no_argument, 0, 'b'},
{"slip", no_argument, 0, 's'},
{0, 0, 0, 0}
};
/* getopt_long stores the option index here. */
int option_index = 0;
int c = getopt_long (argc, argv, "bs",
long_options, &option_index);
/* Detect the end of the options. */
if (c == -1)
break;
switch (c)
{
case 0:
/* If this option set a flag, do nothing else now. */
if (long_options[option_index].flag != 0)
break;
printf ("option %s", long_options[option_index].name);
if (optarg)
printf (" with arg %s", optarg);
printf ("\n");
break;
case 'b':
puts ("option -b\n");
break;
case 's':
puts ("option -s\n");
break;
case '?':
/* getopt_long already printed an error message. */
break;
default:
abort ();
}
}
if (verbose_flag)
puts ("verbose flag is set");
/* Print any remaining command line arguments (not options). */
if (optind < argc)
{
printf ("non-option ARGV-elements: ");
while (optind < argc)
printf ("%s ", argv[optind++]);
putchar ('\n');
}
return 0;
}
Related:
Upvotes: 10
Reputation: 41551
Instead of getopt()
, you may also consider using argp_parse()
(an alternative interface to the same library).
From libc manual:
getopt
is more standard (the short-option only version of it is a part of the POSIX standard), but usingargp_parse
is often easier, both for very simple and very complex option structures, because it does more of the dirty work for you.
But I was always happy with the standard getopt
.
N.B. GNU getopt
with getopt_long
is GNU LGPL.
Upvotes: 5
Reputation: 101299
Other have hit this one on the head:
main(int argc, char **argv)
give you direct access to the command line (after it has been mangled and tokenized by the shell)getopt()
and getopt_long()
but as you've seen the code to use them is a bit wordy, and quite idomatic. I generally push it out of view with something like:
typedef
struct options_struct {
int some_flag;
int other_flage;
char *use_file;
} opt_t;
/* Parses the command line and fills the options structure,
* returns non-zero on error */
int parse_options(opt_t *opts, int argc, char **argv);
Then first thing in main:
int main(int argc, char **argv){
opt_t opts;
if (parse_options(&opts,argc,argv)){
...
}
...
}
Or you could use one of the solutions suggested in Argument-parsing helpers for C/UNIX.
Upvotes: 4
Reputation: 12426
Take a look at the getopt library; it's pretty much the gold standard for this sort of thing.
Upvotes: 7
Reputation: 994797
In C, this is done using arguments passed to your main()
function:
int main(int argc, char *argv[])
{
int i = 0;
for (i = 0; i < argc; i++) {
printf("argv[%d] = %s\n", i, argv[i]);
}
return 0;
}
More information can be found online such as this Arguments to main article.
Upvotes: 29