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/*
strtokeg - skeleton shell using strtok to parse command line
usage:
strtokeg
reads in a line of keyboard input at a time, parsing it into
tokens that are separated by white spaces (set by #define
SEPARATORS).
can use redirected input
if the first token is a recognized internal command, then that
command is executed. otherwise the tokens are printed on the
display.
internal commands:
clear - clears the screen
quit - exits from the program
********************************************************************
version: 1.0
date: December 2003
author: Ian G Graham
School of Information Technology
Griffith University, Gold Coast
ian.graham@griffith.edu.au
copyright (c) Ian G Graham, 2003. All rights reserved.
This code can be used for teaching purposes, but no warranty,
explicit or implicit, is provided.
*******************************************************************/
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX_BUFFER 1024 // max line buffer
#define MAX_ARGS 64 // max # args
#define SEPARATORS " \t\n" // token sparators
int main (int argc, char ** argv)
{
char buf[MAX_BUFFER]; // line buffer
char * args[MAX_ARGS]; // pointers to arg strings
char ** arg; // working pointer thru args
char * prompt = "==>" ; // shell prompt
/* keep reading input until "quit" command or eof of redirected input */
while (!feof(stdin)) {
/* get command line from input */
fputs (prompt, stdout); // write prompt
if (fgets (buf, MAX_BUFFER, stdin )) { // read a line
/* tokenize the input into args array */
arg = args;
*arg++ = strtok(buf,SEPARATORS); // tokenize input
while ((*arg++ = strtok(NULL,SEPARATORS)));
// last entry will be NULL
if (args[0]) { // if there's anything there
/* check for internal/external command */
if (!strcmp(args[0],"clear")) { // "clear" command
system("clear");
continue;
}
if (!strcmp(args[0],"quit")) // "quit" command
break; // break out of 'while' loop
/* else pass command onto OS (or in this instance, print them out) */
arg = args;
while (*arg) fprintf(stdout,"%s ",*arg++);
fputs ("\n", stdout);
}
}
}
return 0;
}
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For use only by students and instructors using the supplementary material available with the text book: "Operating Systems - Internals and Design Principles", William Stallings, Prentice Hall, 5th Edition, 2004. Not to be printed out or copied by any other persons or used for any other purpose without written permission of the author(s).
©