[SOLVED] Parsing getopt (c). How to skip argument?

jmgibson1981 · 05-14-2024, 12:15 PM

Code:

// return struct based on args
REGCHECKS
arg_process(int argc,
            char ** args)
{
   // declare struct and initialize
   REGCHECKS t1;
   init_regchecks_struct(&t1,
                         false,
                         false);

   // load linux version into struct
   // fail if os-release file not found
   if (get_linux_version(&t1) != 0) {
      init_regchecks_struct(&t1,
                            true,
                            true);
      t1.bailout = true;

      return(t1);
   };

   int option = 0;
   int optcounter = 1;
   bool patternbypass = false;
   while ((option = getopt(argc,
                           args, 
                           "ap")) != -1) {
      if (t1.bailout) {
         break;
      }
      switch (option)
      {
         case 'a':
            if (args[optcounter + 1]) {
               t1.architecture = strdup(args[optcounter + 1]);
               optcounter += 2;
            } else {
               init_regchecks_struct(&t1,
                                     true,
                                     true);
            }
            break;
         case 'p':
            // the arg here may start with a -
            if (args[optcounter +1]) {
               test_formatting(args[optcounter + 1],
                               &t1);
               optcounter += 2;
            } else {
               init_regchecks_struct(&t1,
                                     true,
                                     true);
            }
            break;
         default:
            init_regchecks_struct(&t1,
                                  true,
                                  true);
            break;
      }
   }

   return(t1);
}

For the p option sometimes I may want my input to start with a -.

Code:

-p -doc

or some such. is there a way to skip past the next option and ignore it. I tried setting optind + 1 and it works but it ignores any other args. The ultimate goal is to have no specific required order for arguments.

michaelk · 05-14-2024, 12:50 PM

Code:

getopt(argc,args,"ap")

By definition any character followed by a colon (:) requires an argument, two colons means the argument is optional. Since your p is not followed by any colons -doc is not considered a valid argument or even option. I don't think it matters if the argument starts with a -.

It should not matter in what order the -a or -p are entered on the command line. I would guess if you are not following getopt syntax then you need to manually parse your command line arguments.

pan64 · 05-14-2024, 12:57 PM

you need to decide if -p requires an additional parameter, and how do you want to pass it. Usually it should come immediately after the flag, so -a -p -doc is ok, -ap -doc is ok, but -doc -a -p or -p -a -doc or -a -doc -p are not.
Anyway, you need to specify exactly what is expected and allowed and if your requirements are incompatible with getop you need to implement your own parser. Like rsync or ssh.

jmgibson1981 · 05-14-2024, 12:58 PM

That did it. Thank you. i'll need to go over that man page again. missed the part on the colons.

The call would be something like this

Code:

aptsort -a amd64 -p pattern

For now those are the only 2 options I've got on this program. The colons though did it. Works a treat now.

pan64 · 05-14-2024, 01:33 PM

Quote:

Originally Posted by jmgibson1981

That did it. Thank you. The colons though did it. Works a treat now.

In that case you might want to mark the thread as solved.