source: liacs/os/assignment1/simple-shell.c@ 144

/*
 * Rick van der Zwet
 * 0433373
 * OS Assigment 1 - Part B
 * Licence: BSD
 * $Id: simple-shell.c 487 2008-02-20 12:51:08Z rick $
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

int main (int argc, char * argv[]) {

    char **ap;                  /* Argument list pointer */
    char *argv_c[256];          /* argument input list */
    char *bp;                   /* Buffer pointer */
    char *commandsep = " \t";   /* Command seperation characters */
    char *pathsep = ":";        /* Path seperation character */
    char *pathv[256];           /* path list */
    char fullpath[1024] = "";   /* fullpath to binary */
    char inbuf[256];            /* input buffer */
    int argc_c;                 /* Argument list lengh */
    int i;                      /* tmp loop counter */
    int pathc = 0;              /* path list lengh */

    /* Input argument viewer */
    printf("Number of arguments %i\n", argc);
    for (i = 0; i < argc; i++) {
        printf("Command line argument %i: %s\n", i, argv[i]);
    }

    /* put ENV:PATH into path list */
    printf("Env PATH=%s\n", getenv("PATH"));
    bp = getenv("PATH");
    for (ap = pathv;
        (*ap = strsep(&bp, pathsep)) != NULL;) {
        pathc++;
        if (**ap != '\0')
            if (++ap >= &pathv[256])
                break;
    }



    /* Main shell */
    for (;;) {
        /* Get input */
        printf("$ ");
        fgets(inbuf, 256, stdin);
        inbuf[strlen(inbuf) - 1] = '\0';

        /* Convert input to arguments */
        bp = inbuf;
        argc_c = 0;
        for (ap = argv_c;
            (*ap = strsep(&bp, commandsep)) != NULL;) {
            printf("Argument %i : '%s'\n",argc_c, argv_c[argc_c]);
            argc_c++;
            if (**ap != '\0')
                if (++ap >= &argv_c[256])
                    break;
            }

        /* Catch special cases */
        if ( argv_c[0] == '\0' ) {
            printf("No input...\n");
            continue;
        }
        if (strcmp(argv_c[0], "exit") == 0) {
            printf("Goodbye...\n");
            break;
        }

        /* Find proper executable in path */
        for (i = 0; i < pathc; i++) {
            (void)strcpy(fullpath, pathv[i]);
            (void)strcat(fullpath, "/");
            (void)strcat(fullpath, argv_c[0]);
            printf("Searching at '%s': ", fullpath);

            if (access(fullpath, X_OK) == 0) {
                printf("OK\n");
                /* Execute command, using fork */
                int pid = fork();
                if (pid > 0) {
                    wait(NULL);
                    break;
                } else {
                    printf("Executing: %s ", fullpath);
                    for (i = 1; i < argc_c; i++) {
                        printf("%s ",argv_c[i]);
                    }
                    printf("\n");
                    execv(fullpath, argv_c);
                }
            } else {
                printf("FAILED\n");
            }
        }
    }
    return(0);
}