int getsubopt(optionp, tokens, valuep) char **optionp; char *tokens[]; char **valuep;
getsubopt()
is a function to parse suboptions in a flag argument that was initially
parsed by
getopt(3).
These suboptions are separated by commas and may consist of either
a single token,
or a token-value pair separated by an equal sign.
Since commas delimit suboptions in the option string they are not allowed
to be part of the suboption or the value of a suboption.
An example command that uses this syntax is
mount(8),
which allows
you to specify mount parameters with the -o switch as follows :
pepper % mount -o rw,hard,bg,wsize=1024 speed:/usr /usrIn this example there are four suboptions: `rw', `hard', `bg', and `wsize', the last of which has an associated value of 1024.
getsubopt() takes the address of a pointer to the option string, a vector of possible tokens, and the address of a value string pointer. It returns the index of the token that matched the suboption in the input string or -1 if there was no match. If the option string at *optionp contains only one subobtion, getsubopt() updates *optionp to point to the NUL at the end of the string, otherwise it isolates the suboption by replacing the comma seperator with a NUL, and updates *optionp to point to the start of the next suboption. If the suboption has an associated value, getsubopt() updates *valuep to point to the value's first character. Otherwise it sets *valuep to NULL.
The token vector is organized as a series of pointers to null-terminated strings. The end of the token vector is identified by a NULL pointer.
When getsubopt() returns, if *valuep is not NULL, then the suboption processed included a value. The calling program may use this information to determine if the presence or lack of a value for this subobtion is an error.
Additionally, when getsubopt() fails to match the suboption with the tokens in the tokens array, the calling program should decide if this is an error, or if the unrecognized option should be passed on to another program.
The variable addressed by optionp points to the next option to be parsed, or a NUL character if there are no more options.
char *myopts[] = { #define READONLY 0 "ro", #define READWRITE 1 "rw", #define WRITESIZE 2 "wsize", #define READSIZE 3 "rsize", NULL }; main(argc, argv) int argc; char **argv; { int sc, c, errflag; char *options, *value; extern char *optarg; extern int optind; . . . while((c = getopt(argc, argv, "abf:o:")) != -1) { switch (c) { case 'a': /* process a option */ break; case 'b': /* process b option */ break; case 'f': ofile = optarg; break; case '?': errflag++; break; case 'o': options = optarg; while (*options != '\0') { switch(getsubopt(&options,myopts,&value) { case READONLY : /* process ro option */ break; case READWRITE : /* process rw option */ break; case WRITESIZE : /* process wsize option */ if (value == NULL) { error_no_arg(); errflag++; } else write_size = atoi(value); break; case READSIZE : /* process rsize option */ if (value == NULL) { error_no_arg(); errflag++; } else read_size = atoi(value); break; default : /* process unknown token */ error_bad_token(value); errflag++; break; } } break; } } if (errflag) { /* print Usage instructions etc. */ } for (; optind<argc; optind++) { /* process remaining arguments */ } . . . }
White space in tokens or token-value pairs must be protected from the shell by quotes.
Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97