getopt in C++ command line arguments with the options

Question

I am writing a simple program to have -d with a parameter along with the other arguments

I want them run with aa.cc with the following options

aa -d 123 param1 param2 or
aa param1 param2 -d 123

I have written the code in the following way

    /* sample */

    char *level:
    while ((ch = getopt(argc, argv, "d:")) != EOF) {
        switch(ch) {
        case 'd':
            level = optarg;    
            debug = TRUE;
            break;
        default:
            usage();
            /*NOTREACHED*/
        }
    }

It is working fine when given as aa -d 123 param1 param2 but not when given as aa param1 param2 -d 123.

Can anyone please suggest how we can achieve that?

Note that getopt() is documented to return -1 rather than EOF after the last option is processed. The POSIX standard header for getopt() is <unistd.h> and that does not define EOF, so the definition of getopt() was changed (quite a while ago now) to decouple it from the <stdio.h> header. — Jonathan Leffler
– Jonathan Leffler, Commented Dec 22, 2011 at 6:11

Jonathan Leffler · Accepted Answer · 2011-12-22 06:03:34Z

2

Unless you're using the GNU version of getopt(), option arguments (such as -d 123) must precede non-option arguments (such as param1 and param2). (See POSIX 'Utility Conventions'.)

If you're using GNU getopt(), it will scan the entire argument list (up to but not including a -- argument), processing options found after non-options, unless the POSIXLY_CORRECT environment variable is set (in which case it behaves like POSIX getopt(), of course).

If you're not using GNU getopt(), you have to live with options before non-options, or switch to GNU getopt(), or write your own.

answered Dec 22, 2011 at 6:03

Jonathan Leffler

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