getopt to take only one argument

Question

I have a question about getopt in C. I have multiple option flags and am trying to get it to take one argument for everything. The command line will look something like command -a fileName or command -b fileName or command -ab fileName. Basically every command takes in one fileName and if they want to combine commands they should only have to type in one fileName. In getopt the string looks like a:b: and a variable is set to argv[argc -1]. This is fine if it's just one option but fails if there are multiple options (ie command -ab fileName) since : forces users to input an option but :: will make the singe options not force the user to type in an option. Any suggestions?

Answer 1

The optind global variable lets you know how many of the argv strings were used. So one way to approach this problem is to just drop the colons, and use a string like "ab". Here's an example of what the code looks like (adapted from the example in the man page):

int main(int argc, char *argv[])
{
    int ch;
    while ((ch = getopt(argc, argv, "ab")) != -1)
    {
        if (ch == 'a')
            printf("Got A\n");
        else if (ch == 'b')
            printf("Got B\n");
        else
            printf("Got confused\n");
    }

    if (optind != argc-1) 
        printf("You forgot to enter the filename\n");
    else
        printf("File: %s\n", argv[optind]);
}

If you run this with a command line like

./test -ab hello

the output is

Got A
Got B
File: hello