xsh_help.c

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/* xsh_help.c - xsh_help */

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

/*------------------------------------------------------------------------
 * xhs_help - display help message that lists shell commands
 *------------------------------------------------------------------------
 */
shellcmd xsh_help(int nargs, char *args[])
{
    int32   i;
    char    *argv[2];       /* argument vector for call */
    char    *src, *cmp;     /* used for string compare  */
    int32   len;            /* length of a command name */
    int32   maxlen;         /* maximum length of all    */
                    /*   command names      */
    int32   cols;           /* number of columns in the */
                    /*   formatted command list */
    int32   spac;           /* space per column in the  */
                    /*   formatted command list */
    int32   lines;          /* total lines of output in the */
                    /*   formatted command list */
    int32   j;          /* index of commands across one */
                    /*   line of formatted output   */
    
    /* For argument '--help', emit help about the 'help' command    */

    if (nargs == 2 && strncmp(args[1], "--help", 7) == 0) {

        printf("Use:\n");
        printf("\t%s [command]\n", args[0]);
        printf("Description:\n");
        printf("\tProvides a list of shell commands or\n");
        printf("\thelp information for a specific command\n");
        printf("Options:\n");
        printf("\tcommand\tspecific command for which to\n");
        printf("\t\tdisplay help information\n");
        printf("\t--help\tdisplay this help and exit\n");
        return 0;
    }

    /* Check for valid number of arguments */

    if (nargs > 2) {
        fprintf(stderr, "%s: too many arguments\n", args[0]);
        fprintf(stderr, "Try '%s --help' for more information\n",
                args[0]);
        return 1;
    }

    /* Output help for specific command given as an argument */

    if (nargs == 2) {
        for (i = 0; i < ncmd; i++) {
            src = cmdtab[i].cname;
            cmp = args[1];
            while (*src != NULLCH) {
                if (*src != *cmp) {
                    break;
                }
                src++;
                cmp++;
            }
            if ( (*src != NULLCH) || (*cmp != NULLCH) ) {
                continue;
            }

            /* prepare args for shell command */

            argv[0] = args[1];
            argv[1] = "--help";
            (*cmdtab[i].cfunc) (2, argv);
            return 0;
        }
        printf("%s: no such command as '%s'\n", args[0], args[1]);
        return 1;
    }

    /* No arguments -- print a list of shell commands */

    printf("\nshell commands are:\n\n");

    /* Calculate the maximum length of a command name */

    maxlen = 0;
    for (i = 0; i < ncmd; i++) {
        len = strnlen(cmdtab[i].cname, 80);
        if (len > maxlen) {
            maxlen = len;
        }
    }

    /* Calculate the number of command names per line */

    cols = 80/(maxlen+1);
    if (cols > 6) {
        cols = 6;
    }

    /* Calculate the width of a column */

    spac = 80/cols;

    /* Calculate the number of lines of output */

    lines = (ncmd+(cols-1))/cols;

    /* print the lines of command names */

    for (i=0; i<lines; i++) {
        for (j=i; j<ncmd; j+=lines) {
            len = strnlen(cmdtab[j].cname,80);
            printf("%s", cmdtab[j].cname);
            while (len < spac) {
                printf(" ");
                len++;
            }
        }
        printf("\n");
    }
    return 0;
}