getopt() function in C to parse command line arguments Return Value: The getopt() function returns different values: If the option takes a value, that value is pointer to the external variable optarg. '-1' if there are no more options to process..
Likewise, people ask, does Getopt change argv?
If the option has an argument, getopt returns the argument by storing it in the variable optarg . You don't ordinarily need to copy the optarg string, since it is a pointer into the original argv array, not into a static area that might be overwritten.
Also Know, what is Optarg? DESCRIPTION. The optarg, opterr, optind, and optopt variables are used by the getopt() function. optarg indicates an optional parameter to a command line option. opterr can be set to 0 to prevent getopt() from printing error messages.
Herein, how do you use Optarg?
The first, optarg, is used when parsing options that take a name as a parameter (as -s or -f in our example). In those cases, it contains a pointer to that parameter. The second, optind, is the current index into the main function's argument list. It's used to find arguments after all the option processing is done.
What is Optind in Getopt?
The variable optind is the index of the next element of argv to be processed. It is initialized to 1, and getopt() updates it as it processes each element of argv[]. The getopt() function returns the next option character (if one is found) from argv that matches a character in optstring, if any.
Related Question Answers
What does Getopt do in C?
getopt() function in C to parse command line arguments The getopt() function is a builtin function in C and is used to parse command line arguments. Syntax: getopt(int argc, char *const argv[], const char *optstring) optstring is simply a list of characters, each representing a single character option.What is Optind in C?
The optind variable is the index value of the next argument that should be handled by the getopt() function. opterr will let you control if the getopt() function should print errors to the console.What is Optarg in shell script?
getopts obtains options and their arguments from a list of parameters that follows the standard POSIX. 2 option syntax (that is, single letters preceded by a - and possibly followed by an argument value; the single letters may be grouped). Typically, shell scripts use getopts to parse arguments passed to them.What is Getopt_long?
A GNU extension, getopt_long, allows parsing of more readable, multicharacter options, which are introduced by two dashes instead of one. The choice of two dashes allows multicharacter options ( --inum ) to be differentiated from single character options specified together ( -abc ). 
