Getopt

C library function for parsing command-line options getopt() is a POSIX C function used to parse command-line options of the Unix/POSIX style on C. It is a part of the POSIX specification, and is universal to Unix-like systems. It is also the name of a Unix program for parsing command line arguments in shell scripts. History A long-standing issue with command line programs was how to specify options; early programs used many ways of doing so, including single character options (-a), multiple options specified together (-abc is equivalent to -a -b -c), multicharacter options (-inum), options with arguments (-a arg, -inum 3, -a=arg), and different prefix characters (-a, +b, /c). The getopt function was written to be a standard mechanism that all programs could use to parse command-line options so that there would be a common interface on which everyone could depend. As such, the original authors picked out of the variations support for single character options, multiple options specified together, and options with arguments (-a arg or -aarg), all controllable by an option string. getopt dates back to at least 1980 and was first published by AT&T at the 1985 UNIFORUM conference in Dal