Collected from unix standard getopt() source code. getopt() is a function to parse user command lines. You may be familiar with unix command "ls -l". Here "ls" is command program and "-l" is an option. getopt() parses these options like "-l" or "--help" etc. getOpt() source code is shown below.
/* Newsgroups: mod.std.unix Subject: public domain AT&T getopt source Date: 3 Nov 85 19:34:15 GMT Here's something you've all been waiting for: the AT&T public domain source for getopt(3). It is the code which was given out at the 1985 UNIFORUM conference in Dallas. I obtained it by electronic mail directly from AT&T. The people there assure me that it is indeed in the public domain. */ /*LINTLIBRARY*/ extern int strlen(); extern int strcmp(); extern char *strchr(); extern int write(); #define NULL 0 #define EOF (-1) #define ERR(s, c) if(opterr){\ char errbuf[2];\ errbuf[0] = c; errbuf[1] = '\n';\ (void) write(2, argv[0], (unsigned)strlen(argv[0]));\ (void) write(2, s, (unsigned)strlen(s));\ (void) write(2, errbuf, 2);} int opterr = 1; int optind = 1; int optopt; char *optarg; int getopt(argc, argv, opts) int argc; char **argv, *opts; { static int sp = 1; register int c; register char *cp; if(sp == 1) if(optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0') return(EOF); else if(strcmp(argv[optind], "--") == NULL) { optind++; return(EOF); } optopt = c = argv[optind][sp]; if(c == ':' || (cp=strchr(opts, c)) == NULL) { ERR(": illegal option -- ", c); if(argv[optind][++sp] == '\0') { optind++; sp = 1; } return('?'); } if(*++cp == ':') { if(argv[optind][sp+1] != '\0') optarg = &argv[optind++][sp+1]; else if(++optind >= argc) { ERR(": option requires an argument -- ", c); sp = 1; return('?'); } else optarg = argv[optind++]; sp = 1; } else { if(argv[optind][++sp] == '\0') { sp = 1; optind++; } optarg = NULL; } return(c); }
