source: MondoRescue/branches/stable/mindi-busybox/procps/watch.c

/* vi: set sw=4 ts=4: */
/*
 * Mini watch implementation for busybox
 *
 * Copyright (C) 2001 by Michael Habermann <mhabermann@gmx.de>
 * Copyrigjt (C) Mar 16, 2003 Manuel Novoa III   (mjn3@codepoet.org)
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* BB_AUDIT SUSv3 N/A */
/* BB_AUDIT GNU defects -- only option -n is supported. */

#include "libbb.h"

// procps 2.0.18:
// watch [-d] [-n seconds]
//   [--differences[=cumulative]] [--interval=seconds] command
//
// procps-3.2.3:
// watch [-dt] [-n seconds]
//   [--differences[=cumulative]] [--interval=seconds] [--no-title] command
//
// (procps 3.x and procps 2.x are forks, not newer/older versions of the same)

int watch_main(int argc, char **argv);
int watch_main(int argc, char **argv)
{
    unsigned opt;
    unsigned period = 2;
    unsigned cmdlen;
    char *header = NULL;
    char *cmd;
    char *tmp;
    char **p;

    opt_complementary = "-1"; // at least one param please
    opt = getopt32(argv, "+dtn:", &tmp);
    //if (opt & 0x1) // -d (ignore)
    //if (opt & 0x2) // -t
    if (opt & 0x4) period = xatou(tmp);
    argv += optind;

    p = argv;
    cmdlen = 1; // 1 for terminal NUL
    while (*p)
        cmdlen += strlen(*p++) + 1;
    tmp = cmd = xmalloc(cmdlen);
    while (*argv) {
        tmp += sprintf(tmp, " %s", *argv);
        argv++;
    }
    cmd++; // skip initial space

    while (1) {
        printf("\033[H\033[J");
        if (!(opt & 0x2)) { // no -t
            int width, len;
            char *thyme;
            time_t t;

            get_terminal_width_height(STDIN_FILENO, &width, 0);
            header = xrealloc(header, width--);
            // '%-*s' pads header with spaces to the full width
            snprintf(header, width, "Every %ds: %-*s", period, width, cmd);
            time(&t);
            thyme = ctime(&t);
            len = strlen(thyme);
            if (len < width)
                strcpy(header + width - len, thyme);
            puts(header);
        }
        fflush(stdout);
        // TODO: 'real' watch pipes cmd's output to itself
        // and does not allow it to overflow the screen
        // (taking into account linewrap!)
        system(cmd);
        sleep(period);
    }
    return 0; // gcc thinks we can reach this :)
}