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/* getopt.c - get command line options
*
* Parse the command line options, System V style.
*
* Standard option syntax is:
*
* option = -[optLetter,...][argLetter argument]
*
* where
* - there is no space between the '-' and optLetters or argLetters.
* - optLetters and argLetters 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 '-'.
* - upper and lower case letters are distinct.
*
* There may be multiple option clusters on a command line, each
* beginning with a '-', but all must appear before any non-option
* arguments (arguments not introduced by a '-'). optLetters and
* argLetters may be repeated, it is up to the caller to decide
* if that is an error.
*
* The character '-' appearing alone as the last argument is an error.
* The lead-in sequence '--' causes itself and all the rest of the
* line to be ignored (allowing non-options which begin with '-'.
*
* The string *options allows valid optLetters and argLetters 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 '--' is used then optind is stepped to the next argument
* before getopt() returns EOF.
*
* If an error occurs, that is '-' 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
*
* *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:
*
* command -uPFPi -X -A L otherparameters
*
* where:
* - '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.
* - "otherparameters" is not an option, and terminates getOpt. The
* caller may collect remaining arguments using argv pointers.
*/
#include <errno.h>
#include <stdio.h>
#include <string.h>
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 */
int getopt(int argc, char *argv[], char *options)
{
unsigned char ch;
char *optP;
if (argc > optind) {
if (letP == NULL) {
if ((letP = argv[optind]) == NULL ||
*(letP++) != '-') goto gopEOF;
if (*letP == '-') {
optind++; goto gopEOF;
}
}
if (0 == (ch = *(letP++))) {
optind++; goto gopEOF;
}
if (':' == ch || (optP = strchr(options, ch)) == NULL)
goto gopError;
if (':' == *(++optP)) {
optind++;
if (0 == *letP) {
if (argc <= optind) goto gopError;
letP = argv[optind++];
}
optarg = letP;
letP = NULL;
} else {
if (0 == *letP) {
optind++;
letP = NULL;
}
optarg = NULL;
}
return ch;
}
gopEOF:
optarg = letP = NULL;
return EOF;
gopError:
optarg = NULL;
errno = EINVAL;
if (opterr)
perror ("getopt()");
return ('?');
}
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