src/timeout.c

   1 /* timeout -- run a command with bounded time
   2    Copyright (C) 2008-2009 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17
  18 /* timeout - Start a command, and kill it if the specified timeout expires
  19
  20    We try to behave like a shell starting a single (foreground) job,
  21    and will kill the job if we receive the alarm signal we setup.
  22    The exit status of the job is returned, or one of these errors:
  23      EXIT_TIMEDOUT      124      job timed out
  24      EXIT_CANCELED      125      internal error
  25      EXIT_CANNOT_INVOKE 126      error executing job
  26      EXIT_ENOENT        127      couldn't find job to exec
  27
  28    Caveats:
  29      If user specifies the KILL (9) signal is to be sent on timeout,
  30      the monitor is killed and so exits with 128+9 rather than 124.
  31
  32      If you start a command in the background, which reads from the tty
  33      and so is immediately sent SIGTTIN to stop, then the timeout
  34      process will ignore this so it can timeout the command as expected.
  35      This can be seen with `timeout 10 dd&` for example.
  36      However if one brings this group to the foreground with the `fg`
  37      command before the timer expires, the command will remain
  38      in the sTop state as the shell doesn't send a SIGCONT
  39      because the timeout process (group leader) is already running.
  40      To get the command running again one can Ctrl-Z, and do fg again.
  41      Note one can Ctrl-C the whole job when in this state.
  42      I think this could be fixed but I'm not sure the extra
  43      complication is justified for this scenario.
  44
  45    Written by Pádraig Brady.  */
  46
  47 #include <config.h>
  48 #include <getopt.h>
  49 #include <stdio.h>
  50 #include <sys/types.h>
  51 #include <signal.h>
  52
  53 #if HAVE_SYS_WAIT_H
  54 # include <sys/wait.h>
  55 #endif
  56 #ifndef WIFSIGNALED
  57 # define WIFSIGNALED(s) (((s) & 0xFFFF) - 1 < (unsigned int) 0xFF)
  58 #endif
  59 #ifndef WTERMSIG
  60 # define WTERMSIG(s) ((s) & 0x7F)
  61 #endif
  62
  63 #include "system.h"
  64 #include "xstrtol.h"
  65 #include "sig2str.h"
  66 #include "operand2sig.h"
  67 #include "cloexec.h"
  68 #include "error.h"
  69 #include "long-options.h"
  70 #include "quote.h"
  71
  72 #define PROGRAM_NAME "timeout"
  73
  74 #define AUTHORS proper_name_utf8 ("Padraig Brady", "P\303\241draig Brady")
  75
  76 /* Note ETIMEDOUT is 110 on GNU/Linux systems but this is non standard */
  77 #define EXIT_TIMEDOUT 124
  78
  79 /* Internal failure.  */
  80 #define EXIT_CANCELED 125
  81
  82 static int timed_out;
  83 static int term_signal = SIGTERM;  /* same default as kill command.  */
  84 static int monitored_pid;
  85 static int sigs_to_ignore[NSIG];   /* so monitor can ignore sigs it resends.  */
  86
  87 static struct option const long_options[] =
  88 {
  89   {"signal", required_argument, NULL, 's'},
  90   {NULL, 0, NULL, 0}
  91 };
  92
  93 /* send sig to group but not ourselves.
  94  * FIXME: Is there a better way to achieve this?  */
  95 static int
  96 send_sig (int where, int sig)
  97 {
  98   sigs_to_ignore[sig] = 1;
  99   return kill (where, sig);
 100 }
 101
 102 static void
 103 cleanup (int sig)
 104 {
 105   if (sig == SIGALRM)
 106     {
 107       timed_out = 1;
 108       sig = term_signal;
 109     }
 110   if (monitored_pid)
 111     {
 112       if (sigs_to_ignore[sig])
 113         {
 114           sigs_to_ignore[sig] = 0;
 115           return;
 116         }
 117       send_sig (0, sig);
 118       if (sig != SIGKILL && sig != SIGCONT)
 119         send_sig (0, SIGCONT);
 120     }
 121   else /* we're the child or the child is not exec'd yet.  */
 122     _exit (128 + sig);
 123 }
 124
 125 void
 126 usage (int status)
 127 {
 128   if (status != EXIT_SUCCESS)
 129     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 130              program_name);
 131   else
 132     {
 133       printf (_("\
 134 Usage: %s [OPTION] NUMBER[SUFFIX] COMMAND [ARG]...\n\
 135   or:  %s [OPTION]\n"), program_name, program_name);
 136
 137       fputs (_("\
 138 Start COMMAND, and kill it if still running after NUMBER seconds.\n\
 139 SUFFIX may be `s' for seconds (the default), `m' for minutes,\n\
 140 `h' for hours or `d' for days.\n\
 141 \n\
 142 "), stdout);
 143
 144       fputs (_("\
 145 Mandatory arguments to long options are mandatory for short options too.\n\
 146 "), stdout);
 147       fputs (_("\
 148   -s, --signal=SIGNAL\n\
 149                    specify the signal to be sent on timeout.\n\
 150                    SIGNAL may be a name like `HUP' or a number.\n\
 151                    See `kill -l` for a list of signals\n"), stdout);
 152
 153       fputs (HELP_OPTION_DESCRIPTION, stdout);
 154       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 155       fputs (_("\n\
 156 If the command times out, then we exit with status 124,\n\
 157 otherwise the normal exit status of the command is returned.\n\
 158 If no signal is specified, the TERM signal is sent. The TERM signal\n\
 159 will kill processes which do not catch this signal. For other processes,\n\
 160 it may be necessary to use the KILL (9) signal, since this signal cannot\n\
 161 be caught.\n"), stdout);
 162       emit_bug_reporting_address ();
 163     }
 164   exit (status);
 165 }
 166
 167 /* Given a long integer value *X, and a suffix character, SUFFIX_CHAR,
 168    scale *X by the multiplier implied by SUFFIX_CHAR.  SUFFIX_CHAR may
 169    be the NUL byte or `s' to denote seconds, `m' for minutes, `h' for
 170    hours, or `d' for days.  If SUFFIX_CHAR is invalid, don't modify *X
 171    and return false.  If *X would overflow an integer, don't modify *X
 172    and return false. Otherwise return true.  */
 173
 174 static bool
 175 apply_time_suffix (unsigned long *x, char suffix_char)
 176 {
 177   unsigned int multiplier = 1;
 178
 179   switch (suffix_char)
 180     {
 181     case 0:
 182     case 's':
 183       return true;
 184     case 'd':
 185       multiplier *= 24;
 186     case 'h':
 187       multiplier *= 60;
 188     case 'm':
 189       if (multiplier > UINT_MAX / 60) /* 16 bit overflow */
 190         return false;
 191       multiplier *= 60;
 192       break;
 193     default:
 194       return false;
 195     }
 196
 197   if (*x > UINT_MAX / multiplier)
 198     return false;
 199
 200   *x *= multiplier;
 201
 202   return true;
 203 }
 204
 205 static void
 206 install_signal_handlers (void)
 207 {
 208   struct sigaction sa;
 209   sigemptyset(&sa.sa_mask);  /* Allow concurrent calls to handler */
 210   sa.sa_handler = cleanup;
 211   sa.sa_flags = SA_RESTART;  /* restart syscalls (like wait() below) */
 212
 213   sigaction (SIGALRM, &sa, NULL); /* our timeout.  */
 214   sigaction (SIGINT, &sa, NULL);  /* Ctrl-C at terminal for example.  */
 215   sigaction (SIGQUIT, &sa, NULL); /* Ctrl-\ at terminal for example.  */
 216   sigaction (SIGTERM, &sa, NULL); /* if we're killed, stop monitored proc.  */
 217   sigaction (SIGHUP, &sa, NULL);  /* terminal closed for example.  */
 218 }
 219
 220 int
 221 main (int argc, char **argv)
 222 {
 223   unsigned long timeout;
 224   char signame[SIG2STR_MAX];
 225   int c;
 226   char *ep;
 227
 228   initialize_main (&argc, &argv);
 229   set_program_name (argv[0]);
 230   setlocale (LC_ALL, "");
 231   bindtextdomain (PACKAGE, LOCALEDIR);
 232   textdomain (PACKAGE);
 233
 234   initialize_exit_failure (EXIT_CANCELED);
 235   atexit (close_stdout);
 236
 237   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
 238                       usage, AUTHORS, (char const *) NULL);
 239
 240   while ((c = getopt_long (argc, argv, "+s:", long_options, NULL)) != -1)
 241     {
 242       switch (c)
 243         {
 244         case 's':
 245           term_signal = operand2sig (optarg, signame);
 246           if (term_signal == -1)
 247             usage (EXIT_CANCELED);
 248           break;
 249         default:
 250           usage (EXIT_CANCELED);
 251           break;
 252         }
 253     }
 254
 255   if (argc - optind < 2)
 256     usage (EXIT_CANCELED);
 257
 258   if (xstrtoul (argv[optind], &ep, 10, &timeout, NULL)
 259       /* Invalid interval. Note 0 disables timeout  */
 260       || (timeout > UINT_MAX)
 261       /* Extra chars after the number and an optional s,m,h,d char.  */
 262       || (*ep && *(ep + 1))
 263       /* Check any suffix char and update timeout based on the suffix.  */
 264       || !apply_time_suffix (&timeout, *ep))
 265     {
 266       error (0, 0, _("invalid time interval %s"), quote (argv[optind]));
 267       usage (EXIT_CANCELED);
 268     }
 269   optind++;
 270
 271   argc -= optind;
 272   argv += optind;
 273
 274   /* Ensure we're in our own group so all subprocesses can be killed.
 275      Note we don't just put the child in a separate group as
 276      then we would need to worry about foreground and background groups
 277      and propagating signals between them.  */
 278   setpgid (0, 0);
 279
 280   /* Setup handlers before fork() so that we
 281      handle any signals caused by child, without races.  */
 282   install_signal_handlers ();
 283   signal (SIGTTIN, SIG_IGN);    /* don't sTop if background child needs tty.  */
 284   signal (SIGTTOU, SIG_IGN);    /* don't sTop if background child needs tty.  */
 285
 286   monitored_pid = fork ();
 287   if (monitored_pid == -1)
 288     {
 289       error (0, errno, _("fork system call failed"));
 290       return EXIT_CANCELED;
 291     }
 292   else if (monitored_pid == 0)
 293     {                           /* child */
 294       int exit_status;
 295
 296       /* exec doesn't reset SIG_IGN -> SIG_DFL.  */
 297       signal (SIGTTIN, SIG_DFL);
 298       signal (SIGTTOU, SIG_DFL);
 299
 300       execvp (argv[0], argv);   /* FIXME: should we use "sh -c" ... here?  */
 301
 302       /* exit like sh, env, nohup, ...  */
 303       exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 304       error (0, errno, _("failed to run command %s"), quote (argv[0]));
 305       return exit_status;
 306     }
 307   else
 308     {
 309       int status;
 310
 311       alarm (timeout);
 312
 313       /* We're just waiting for a single process here, so wait() suffices.
 314          Note the signal() calls above on GNU/Linux and BSD at least,
 315          essentially call the lower level sigaction() with the SA_RESTART flag
 316          set, which ensures the following wait call will only return if the
 317          child exits, not on this process receiving a signal. Also we're not
 318          passing WUNTRACED | WCONTINUED to a waitpid() call and so will not get
 319          indication that the child has stopped or continued.  */
 320       wait (&status);
 321
 322       if (WIFEXITED (status))
 323         status = WEXITSTATUS (status);
 324       else if (WIFSIGNALED (status))
 325         status = WTERMSIG (status) + 128;     /* what sh does at least.  */
 326
 327       if (timed_out)
 328         return EXIT_TIMEDOUT;
 329       else
 330         return status;
 331     }
 332 }