xsh_kill.c

Go to the documentation of this file.

/* xsh_kill.c - xsh_kill */

#include <xinu.h>
#include <string.h>
#include <stdio.h>

/*------------------------------------------------------------------------
 * xsh_kill - obtain and print the current month, day, year, and time
 *------------------------------------------------------------------------
 */
shellcmd xsh_kill(int nargs, char *args[]) {

    int32   retval;         /* return value         */
    pid32   pid;            /* ID of process to kill    */
    char    ch;         /* next character of argument   */
    char    *chptr;         /* walks along argument string  */

    /* Output info for '--help' argument */

    if (nargs == 2 && strncmp(args[1], "--help", 7) == 0) {
        printf("Usage: %s PID\n\n", args[0]);
        printf("Description:\n");
        printf("\tterminates a process\n");
        printf("Options:\n");
        printf("\tPID \tthe ID of a process to terminate\n");
        printf("\t--help\tdisplay this help and exit\n");
        return OK;
    }

    /* Check argument count */

    if (nargs != 2) {
        fprintf(stderr, "%s: incorrect argument\n", args[0]);
        fprintf(stderr, "Try '%s --help' for more information\n",
            args[0]);
        return SYSERR;
    }

    /* compute process ID from argument string */

    chptr = args[1];
    ch = *chptr++;
    pid = 0;
    while(ch != NULLCH) {
        if ( (ch < '0') || (ch > '9') ) {
            fprintf(stderr, "%s: non-digit in process ID\n",
                args[0]);
            return 1;
        }
        pid = 10*pid + (ch - '0');
        ch = *chptr++;
    }
    if (pid == 0) {
        fprintf(stderr, "%s: cannot kill the null process\n",
            args[0]);
        return 1;
    }

    retval = kill(pid);
    if (retval == SYSERR) {
        fprintf(stderr, "%s: cannot kill process %d\n",
            args[0], pid);
        return 1;
    }
    return 0;
}