I am working on trying to take in command line arguments. If I want to have multiple optional command line arguments how would I go about doing that? For example you can run the program in the following ways: (a is required every instance but -b -c -d can be given optionally and in any order)
./myprogram -a
./myprogram -a -c -d
./myprogram -a -d -b
I know that getopt()'s third argument is options. I can set these options to be "abc" but will the way I have my switch case set up causes the loop to break at each option.
The order doesn't matter so far as getopt() is concerned. All that matters is your third argument to getopt() (ie: it's format string) is correct:
The follow format strings are all equivalent:
"c:ba"
"c:ab"
"ac:b"
"abc:"
In your particular case, the format string just needs to be something like "abcd", and the switch() statement is properly populated.
The following minimal example¹ will help.
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main (int argc, char **argv)
{
int aflag = 0;
int bflag = 0;
char *cvalue = NULL;
int index;
int c;
opterr = 0;
while ((c = getopt (argc, argv, "abc:")) != -1)
{
switch (c)
{
case 'a':
aflag = 1;
break;
case 'b':
bflag = 1;
break;
case 'c':
cvalue = optarg;
break;
case '?':
if (optopt == 'c')
fprintf (stderr, "Option -%c requires an argument.\n", optopt);
else 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 ("aflag = %d, bflag = %d, cvalue = %s\n",
aflag, bflag, cvalue);
for (index = optind; index < argc; index++)
printf ("Non-option argument %s\n", argv[index]);
return 0;
}