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 //config:config WATCH
  15 //config:       bool "watch (4.1 kb)"
  16 //config:       default y
  17 //config:       help
  18 //config:       watch is used to execute a program periodically, showing
  19 //config:       output to the screen.
  20
  21 //applet:IF_WATCH(APPLET(watch, BB_DIR_BIN, BB_SUID_DROP))
  22
  23 //kbuild:lib-$(CONFIG_WATCH) += watch.o
  24
  25 //usage:#define watch_trivial_usage
  26 //usage:       "[-n SEC] [-t] PROG ARGS"
  27 //usage:#define watch_full_usage "\n\n"
  28 //usage:       "Run PROG periodically\n"
  29 //usage:     "\n        -n      Loop period in seconds (default 2)"
  30 //usage:     "\n        -t      Don't print header"
  31 //usage:
  32 //usage:#define watch_example_usage
  33 //usage:       "$ watch date\n"
  34 //usage:       "Mon Dec 17 10:31:40 GMT 2000\n"
  35 //usage:       "Mon Dec 17 10:31:42 GMT 2000\n"
  36 //usage:       "Mon Dec 17 10:31:44 GMT 2000"
  37
  38 #include "libbb.h"
  39
  40 // procps 2.0.18:
  41 // watch [-d] [-n seconds]
  42 //   [--differences[=cumulative]] [--interval=seconds] command
  43 //
  44 // procps-3.2.3:
  45 // watch [-dt] [-n seconds]
  46 //   [--differences[=cumulative]] [--interval=seconds] [--no-title] command
  47 //
  48 // (procps 3.x and procps 2.x are forks, not newer/older versions of the same)
  49
  50 int watch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  51 int watch_main(int argc UNUSED_PARAM, char **argv)
  52 {
  53         unsigned opt;
  54         unsigned period = 2;
  55         unsigned width, new_width;
  56         char *header;
  57         char *cmd;
  58
  59 #if 0 // maybe ENABLE_DESKTOP?
  60         // procps3 compat - "echo TEST | watch cat" doesn't show TEST:
  61         close(STDIN_FILENO);
  62         xopen("/dev/null", O_RDONLY);
  63 #endif
  64
  65         opt_complementary = "-1"; // at least one param; -n NUM
  66         // "+": stop at first non-option (procps 3.x only)
  67         opt = getopt32(argv, "+dtn:+", &period);
  68         argv += optind;
  69
  70         // watch from both procps 2.x and 3.x does concatenation. Example:
  71         // watch ls -l "a /tmp" "2>&1" - ls won't see "a /tmp" as one param
  72         cmd = *argv;
  73         while (*++argv)
  74                 cmd = xasprintf("%s %s", cmd, *argv); // leaks cmd
  75
  76         width = (unsigned)-1; // make sure first time new_width != width
  77         header = NULL;
  78         while (1) {
  79                 /* home; clear to the end of screen */
  80                 printf("\033[H""\033[J");
  81                 if (!(opt & 0x2)) { // no -t
  82                         const unsigned time_len = sizeof("1234-67-90 23:56:89");
  83
  84                         // STDERR_FILENO is procps3 compat:
  85                         // "watch ls 2>/dev/null" does not detect tty size
  86                         new_width = get_terminal_width(STDERR_FILENO);
  87                         if (new_width != width) {
  88                                 width = new_width;
  89                                 free(header);
  90                                 header = xasprintf("Every %us: %-*s", period, (int)width, cmd);
  91                         }
  92                         if (time_len < width) {
  93                                 strftime_YYYYMMDDHHMMSS(
  94                                         header + width - time_len,
  95                                         time_len,
  96                                         /*time_t*:*/ NULL
  97                                 );
  98                         }
  99
 100                         // compat: empty line between header and cmd output
 101                         printf("%s\n\n", header);
 102                 }
 103                 fflush_all();
 104                 // TODO: 'real' watch pipes cmd's output to itself
 105                 // and does not allow it to overflow the screen
 106                 // (taking into account linewrap!)
 107                 system(cmd);
 108                 sleep(period);
 109         }
 110         return 0; // gcc thinks we can reach this :)
 111 }