Monday, April 18, 2011

getopt() source code C/C++.

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);
}