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 //config:config WATCH
  11 //config:       bool "watch (4.4 kb)"
  12 //config:       default y
  13 //config:       help
  14 //config:       watch is used to execute a program periodically, showing
  15 //config:       output to the screen.
  16
  17 //applet:IF_WATCH(APPLET(watch, BB_DIR_BIN, BB_SUID_DROP))
  18
  19 //kbuild:lib-$(CONFIG_WATCH) += watch.o
  20
  21 //usage:#define watch_trivial_usage
  22 //usage:       "[-n SEC] [-t] PROG ARGS"
  23 //usage:#define watch_full_usage "\n\n"
  24 //usage:       "Run PROG periodically\n"
  25 //usage:     "\n        -n      Loop period in seconds (default 2)"
  26 //usage:     "\n        -t      Don't print header"
  27 //usage:
  28 //usage:#define watch_example_usage
  29 //usage:       "$ watch date\n"
  30 //usage:       "Mon Dec 17 10:31:40 GMT 2000\n"
  31 //usage:       "Mon Dec 17 10:31:42 GMT 2000\n"
  32 //usage:       "Mon Dec 17 10:31:44 GMT 2000"
  33
  34 /* BB_AUDIT SUSv3 N/A */
  35 /* BB_AUDIT GNU defects -- only option -n is supported. */
  36
  37 #include "libbb.h"
  38
  39 #define ESC "\033"
  40
  41 // procps 2.0.18:
  42 // watch [-d] [-n seconds]
  43 //   [--differences[=cumulative]] [--interval=seconds] command
  44 //
  45 // procps-3.2.3:
  46 // watch [-dt] [-n seconds]
  47 //   [--differences[=cumulative]] [--interval=seconds] [--no-title] command
  48 //
  49 // (procps 3.x and procps 2.x are forks, not newer/older versions of the same)
  50
  51 int watch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  52 int watch_main(int argc UNUSED_PARAM, char **argv)
  53 {
  54         unsigned opt;
  55         unsigned period = 2;
  56         unsigned width, new_width;
  57         char *header;
  58         char *cmd;
  59
  60 #if 0 // maybe ENABLE_DESKTOP?
  61         // procps3 compat - "echo TEST | watch cat" doesn't show TEST:
  62         close(STDIN_FILENO);
  63         xopen("/dev/null", O_RDONLY);
  64 #endif
  65
  66         // "+": stop at first non-option (procps 3.x only); -n NUM
  67         // at least one param
  68         opt = getopt32(argv, "^+" "dtn:+" "\0" "-1", &period);
  69         argv += optind;
  70
  71         // watch from both procps 2.x and 3.x does concatenation. Example:
  72         // watch ls -l "a /tmp" "2>&1" - ls won't see "a /tmp" as one param
  73         cmd = *argv;
  74         while (*++argv)
  75                 cmd = xasprintf("%s %s", cmd, *argv); // leaks cmd
  76
  77         width = (unsigned)-1; // make sure first time new_width != width
  78         header = NULL;
  79         while (1) {
  80                 /* home; clear to the end of screen */
  81                 printf(ESC"[H" ESC"[J");
  82                 if (!(opt & 0x2)) { // no -t
  83                         const unsigned time_len = sizeof("1234-67-90 23:56:89");
  84
  85                         // STDERR_FILENO is procps3 compat:
  86                         // "watch ls 2>/dev/null" does not detect tty size
  87                         new_width = get_terminal_width(STDERR_FILENO);
  88                         if (new_width != width) {
  89                                 width = new_width;
  90                                 free(header);
  91                                 header = xasprintf("Every %us: %-*s", period, (int)width, cmd);
  92                         }
  93                         if (time_len < width) {
  94                                 strftime_YYYYMMDDHHMMSS(
  95                                         header + width - time_len,
  96                                         time_len,
  97                                         /*time_t*:*/ NULL
  98                                 );
  99                         }
 100
 101                         // compat: empty line between header and cmd output
 102                         printf("%s\n\n", header);
 103                 }
 104                 fflush_all();
 105                 // TODO: 'real' watch pipes cmd's output to itself
 106                 // and does not allow it to overflow the screen
 107                 // (taking into account linewrap!)
 108                 system(cmd);
 109                 sleep(period);
 110         }
 111         return 0; // gcc thinks we can reach this :)
 112 }