Category : Music and Digitized Voice
Archive   : SBF3.ZIP
Filename : GETOPT.C

Output of file : GETOPT.C contained in archive : SBF3.ZIP

Copyright (c) 1986,1991 by Borland International Inc.
All Rights Reserved.


int optind = 1; /* index of which argument is next */
char *optarg; /* pointer to argument of current option */
int opterr = 1; /* allow error message */

static char *letP = NULL; /* remember next option char's location */
static char SW = '-'; /* DOS switch character, either '-' or '/' */

Parse the command line options, System V style.

Standard option syntax is:

option ::= SW [optLetter]* [argLetter space* argument]

- SW is either '/' or '-', according to the current setting
of the MSDOS switchar (int 21h function 37h).
- there is no space before any optLetter or argLetter.
- opt/arg letters are alphabetic, not punctuation characters.
- optLetters, if present, must be matched in optionS.
- argLetters, if present, are found in optionS followed by ':'.
- argument is any white-space delimited string. Note that it
can include the SW character.
- upper and lower case letters are distinct.

There may be multiple option clusters on a command line, each
beginning with a SW, but all must appear before any non-option
arguments (arguments not introduced by SW). Opt/arg letters may
be repeated: it is up to the caller to decide if that is an error.

The character SW appearing alone as the last argument is an error.
The lead-in sequence SWSW ("--" or "//") causes itself and all the
rest of the line to be ignored (allowing non-options which begin
with the switch char).

The string *optionS allows valid opt/arg letters to be recognized.
argLetters are followed with ':'. Getopt () returns the value of
the option character found, or EOF if no more options are in the
command line. If option is an argLetter then the global optarg is
set to point to the argument string (having skipped any white-space).

The global optind is initially 1 and is always left as the index
of the next argument of argv[] which getopt has not taken. Note
that if "--" or "//" are used then optind is stepped to the next
argument before getopt() returns EOF.

If an error occurs, that is an SW char precedes an unknown letter,
then getopt() will return a '?' character and normally prints an
error message via perror(). If the global variable opterr is set
to false (zero) before calling getopt() then the error message is
not printed.

For example, if the MSDOS switch char is '/' (the MSDOS norm) and

*optionS == "A:F:PuU:wXZ:"

then 'P', 'u', 'w', and 'X' are option letters and 'F', 'U', 'Z'
are followed by arguments. A valid command line may be:

aCommand /uPFPi /X /A L someFile

- 'u' and 'P' will be returned as isolated option letters.
- 'F' will return with "Pi" as its argument string.
- 'X' is an isolated option.
- 'A' will return with "L" as its argument.
- "someFile" is not an option, and terminates getOpt. The
caller may collect remaining arguments using argv pointers.

int getopt(int argc, char *argv[], char *optionS)
unsigned char ch;
char *optP;

if (SW == 0) {
/* get SW using dos call 0x37 */
_AX = 0x3700;
SW = _DL;

if (argc > optind) {
if (letP == NULL) {
if ((letP = argv[optind]) == NULL ||
*(letP++) != SW) goto gopEOF;
if (*letP == SW) {
optind++; goto gopEOF;
if (0 == (ch = *(letP++))) {
optind++; goto gopEOF;
if (':' == ch || (optP = strchr(optionS, ch)) == NULL)
goto gopError;
if (':' == *(++optP)) {
if (0 == *letP) {
if (argc <= optind) goto gopError;
letP = argv[optind++];
optarg = letP;
letP = NULL;
} else {
if (0 == *letP) {
letP = NULL;
optarg = NULL;
return ch;
optarg = letP = NULL;
return EOF;

optarg = NULL;
errno = EINVAL;
if (opterr)
perror ("get command line option");
return ('?');