procps/watch.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini watch implementation for busybox
   4  *
   5  * Copyright (C) 2001 by Michael Habermann <mhabermann@gmx.de>
   6  * Copyrigjt (C) Mar 16, 2003 Manuel Novoa III   (mjn3@codepoet.org)
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9  */
  10
  11 /* BB_AUDIT SUSv3 N/A */
  12 /* BB_AUDIT GNU defects -- only option -n is supported. */
  13
  14 //usage:#define watch_trivial_usage
  15 //usage:       "[-n SEC] [-t] PROG ARGS"
  16 //usage:#define watch_full_usage "\n\n"
  17 //usage:       "Run PROG periodically\n"
  18 //usage:     "\n        -n      Loop period in seconds (default 2)"
  19 //usage:     "\n        -t      Don't print header"
  20 //usage:
  21 //usage:#define watch_example_usage
  22 //usage:       "$ watch date\n"
  23 //usage:       "Mon Dec 17 10:31:40 GMT 2000\n"
  24 //usage:       "Mon Dec 17 10:31:42 GMT 2000\n"
  25 //usage:       "Mon Dec 17 10:31:44 GMT 2000"
  26
  27 #include "libbb.h"
  28
  29 // procps 2.0.18:
  30 // watch [-d] [-n seconds]
  31 //   [--differences[=cumulative]] [--interval=seconds] command
  32 //
  33 // procps-3.2.3:
  34 // watch [-dt] [-n seconds]
  35 //   [--differences[=cumulative]] [--interval=seconds] [--no-title] command
  36 //
  37 // (procps 3.x and procps 2.x are forks, not newer/older versions of the same)
  38
  39 int watch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  40 int watch_main(int argc UNUSED_PARAM, char **argv)
  41 {
  42         unsigned opt;
  43         unsigned period = 2;
  44         unsigned width, new_width;
  45         char *header;
  46         char *cmd;
  47
  48 #if 0 // maybe ENABLE_DESKTOP?
  49         // procps3 compat - "echo TEST | watch cat" doesn't show TEST:
  50         close(STDIN_FILENO);
  51         xopen("/dev/null", O_RDONLY);
  52 #endif
  53
  54         opt_complementary = "-1:n+"; // at least one param; -n NUM
  55         // "+": stop at first non-option (procps 3.x only)
  56         opt = getopt32(argv, "+dtn:", &period);
  57         argv += optind;
  58
  59         // watch from both procps 2.x and 3.x does concatenation. Example:
  60         // watch ls -l "a /tmp" "2>&1" - ls won't see "a /tmp" as one param
  61         cmd = *argv;
  62         while (*++argv)
  63                 cmd = xasprintf("%s %s", cmd, *argv); // leaks cmd
  64
  65         width = (unsigned)-1; // make sure first time new_width != width
  66         header = NULL;
  67         while (1) {
  68                 /* home; clear to the end of screen */
  69                 printf("\033[H""\033[J");
  70                 if (!(opt & 0x2)) { // no -t
  71                         const unsigned time_len = sizeof("1234-67-90 23:56:89");
  72
  73                         // STDERR_FILENO is procps3 compat:
  74                         // "watch ls 2>/dev/null" does not detect tty size
  75                         get_terminal_width_height(STDERR_FILENO, &new_width, NULL);
  76                         if (new_width != width) {
  77                                 width = new_width;
  78                                 free(header);
  79                                 header = xasprintf("Every %us: %-*s", period, (int)width, cmd);
  80                         }
  81                         if (time_len < width) {
  82                                 strftime_YYYYMMDDHHMMSS(
  83                                         header + width - time_len,
  84                                         time_len,
  85                                         /*time_t*:*/ NULL
  86                                 );
  87                         }
  88
  89                         // compat: empty line between header and cmd output
  90                         printf("%s\n\n", header);
  91                 }
  92                 fflush_all();
  93                 // TODO: 'real' watch pipes cmd's output to itself
  94                 // and does not allow it to overflow the screen
  95                 // (taking into account linewrap!)
  96                 system(cmd);
  97                 sleep(period);
  98         }
  99         return 0; // gcc thinks we can reach this :)
 100 }