Timeout a command in bash without unnecessary delay

Question

This answer to Command line command to auto-kill a command after a certain amount of time proposes a 1-line method to timeout a long-running command from the bash command line     path to slow command with options    amp  sleep 5   kill     But it s possible that a given  quot long-running quot  command may finish earlier than the timeout   Let s call it a  quot typically-long-running-but-sometimes-fast quot  command  or tlrbsf for fun   So this nifty 1-liner approach has a couple of problems  First  the sleep isn t conditional  so that sets an undesirable lower bound on the time taken for the sequence to finish  Consider 30s or 2m or even 5m for the sleep  when the tlrbsf command finishes in 2 seconds     highly undesirable  Second  the kill is unconditional  so this sequence will attempt to kill a non-running process and whine about it  So    Is there a way to timeout a typically-long-running-but-sometimes-fast   quot tlrbsf quot   command that  has a bash implementation  the other question already has Perl and C answers  will terminate at the earlier of the two  tlrbsf program termination  or timeout elapsed will not kill non-existing non-running processes  or  optionally  will not complain about a bad kill  doesn t have to be a 1-liner can run under Cygwin or Linux      and  for bonus points  runs the tlrbsf command in the foreground any  sleep  or extra process in the background  such that the stdin stdout stderr of the tlrbsf command can be redirected  same as if it had been run directly  If so  please share your code  If not  please explain why  I have spent awhile trying to hack the aforementioned example but I m hitting the limit of my bash skills

User · Answer

This solution works regardless of bash monitor mode. You can use the proper signal to terminate your_command

#!/bin/sh
( your_command ) & pid=$!
( sleep $TIMEOUT && kill -HUP $pid ) 2>/dev/null & watcher=$!
wait $pid 2>/dev/null && pkill -HUP -P $watcher

The watcher kills your_command after given timeout; the script waits for the slow task and terminates the watcher. Note that wait does not work with processes which are children of a different shell.

Examples:

your_command runs more than 2 seconds and was terminated

your_command interrupted

( sleep 20 ) & pid=$!
( sleep 2 && kill -HUP $pid ) 2>/dev/null & watcher=$!
if wait $pid 2>/dev/null; then
    echo "your_command finished"
    pkill -HUP -P $watcher
    wait $watcher
else
    echo "your_command interrupted"
fi

your_command finished before the timeout (20 seconds)

your_command finished

( sleep 2 ) & pid=$!
( sleep 20 && kill -HUP $pid ) 2>/dev/null & watcher=$!
if wait $pid 2>/dev/null; then
    echo "your_command finished"
    pkill -HUP -P $watcher
    wait $watcher
else
    echo "your_command interrupted"
fi

User · Answer

You can do this entirely with bash 4 3 and above    timeout       set  b  sleep   1   amp       2    amp  wait -n  r     kill -9  jobs -p   exit  r         Example   timeout 5 longrunning command args Example     timeout 5 producer    echo KABOOM         consumer Example  producer      timeout 5 consumer1  consumer2    Example    while date  do sleep  3  done       timeout 5 cat   less Needs Bash 4 3 for wait -n Gives 137 if the command was killed  else the return value of the command  Works for pipes    You do not need to go foreground here   Works with internal shell commands or functions  too  Runs in a subshell  so no variable export into the current shell  sorry    If you do not need the return code  this can be made even simpler    timeout       set  b  sleep   1   amp       2    amp  wait -n  kill -9  jobs -p         Notes    Strictly speaking you do not need the   in      however it makes thing more consistent to the    -case   And the set  b probably can be left away  too  but better safe than sorry  Except for --forground  probably  you can implement all variants timeout supports   --preserve-status is a bit difficult  though   This is left as an exercise for the reader      This recipe can be used  naturally  in the shell  as natural as for flock fd      set  b sleep 20  amp    YOUR SHELL CODE HERE    amp  wait -n kill  jobs -p      However  as explained above  you cannot re-export environment variables into the enclosing shell this way naturally   Edit   Real world example  Time out   git ps1 in case it takes too long  for things like slow SSHFS-Links    eval    orig  declare -f   git ps1    amp  amp    git ps1       git      timeout 0 3  usr bin git           timeout 0 3   orig  git ps1             Edit2  Bugfix   I noticed that exit 137 is not needed and makes  timeout unreliable at the same time   Edit3  git is a die-hard  so it needs a double-trick to work satisfyingly   Edit4  Forgot a   in the first  timeout for the real world GIT example

User · Answer

Kinda hacky  but it works   Doesn t work if you have other foreground processes  please help me fix this    sleep TIMEOUT  amp  SPID        YOUR COMMAND HERE  kill   SPID    amp  CPID       fg 1  kill   CPID    Actually  I think you can reverse it  meeting your  bonus  criteria    YOUR COMMAND HERE  amp  SPID        sleep TIMEOUT  kill   SPID    amp  CPID       fg 1  kill   CPID    lt  asdf  gt  fdsa

User · Answer

The timeout command itself has a --foreground option  This lets the command interact with the user  quot when not running timeout directly from a shell prompt quot   timeout --foreground the command its options  I think the questioner must have been aware of the very obvious solution of the timeout command  but asked for an alternate solution for this reason  timeout did not work for me when I called it using popen  i e   not directly from the shell   However  let me not assume that this may have been the reason in the questioner s case  Take a look at its man page

User · Answer

I think this is precisely what you are asking for   http   www bashcookbook com bashinfo source bash-4 0 examples scripts timeout3     bin bash     The Bash shell script executes a command with a time-out    Upon time-out expiration SIGTERM  15  is sent to the process  If the signal   is blocked  then the subsequent SIGKILL  9  terminates it      Based on the Bash documentation example     Hello Chet    please find attached a  little easier    -   to comprehend   time-out example   If you find it suitable  feel free to include   anywhere  the very same logic as in the original examples scripts  a   little more transparent implementation to my taste      Dmitry V Golovashkin  lt Dmitry Golovashkin sas com gt   scriptName    0        declare -i DEFAULT TIMEOUT 9 declare -i DEFAULT INTERVAL 1 declare -i DEFAULT DELAY 1    Timeout  declare -i timeout DEFAULT TIMEOUT   Interval between checks if the process is still alive  declare -i interval DEFAULT INTERVAL   Delay between posting the SIGTERM signal and destroying the process by SIGKILL  declare -i delay DEFAULT DELAY  function printUsage         cat  lt  lt EOF  Synopsis      scriptName  -t timeout   -i interval   -d delay  command     Execute a command with a time-out      Upon time-out expiration SIGTERM  15  is sent to the process  If SIGTERM     signal is blocked  then the subsequent SIGKILL  9  terminates it       -t timeout         Number of seconds to wait for command completion          Default value   DEFAULT TIMEOUT seconds       -i interval         Interval between checks if the process is still alive          Positive integer  default value   DEFAULT INTERVAL seconds       -d delay         Delay between posting the SIGTERM signal and destroying the         process by SIGKILL  Default value   DEFAULT DELAY seconds   As of today  Bash does not support floating point arithmetic  sleep does   therefore all delay time values must be integers  EOF      Options  while getopts   t i d   option  do     case   option  in         t  timeout  OPTARG            i  interval  OPTARG            d  delay  OPTARG               printUsage  exit 1        esac done shift    OPTIND - 1         should be at least 1  the command to execute   however it may be strictly   greater than 1 if the command itself has options  if         0    interval  lt   0    then     printUsage     exit 1 fi    kill -0 pid   Exit code indicates if a signal may be sent to  pid process          t   timeout        while   t  gt  0    do         sleep  interval         kill -0       exit 0           t -  interval       done        Be nice  post SIGTERM first        The  exit 0  below will be executed if any preceeding command fails      kill -s SIGTERM     amp  amp  kill -0       exit 0     sleep  delay     kill -s SIGKILL      2 gt   dev null  amp   exec

User · Answer

You are probably looking for the timeout command in coreutils  Since it s a part of coreutils  it is technically a C solution  but it s still coreutils  info timeout for more details  Here s an example   timeout 5  path to slow command with options

User · Answer

There s also cratimeout by Martin Cracauer  written in C for Unix and Linux systems      cf  http   www cons org cracauer software html   usage  cratimeout timeout in msec cmd args cratimeout 5000 sleep 1 cratimeout 5000 sleep 600 cratimeout 5000 tail -f  dev null cratimeout 5000 sh -c  while sleep 1  do date  done

User · Answer

See also the http   www pixelbeat org scripts timeout script the functionality of which has been integrated into newer coreutils

User · Answer

timeout is probably the first approach to try  You may need notification or another command to execute if it times out  After quite a bit of searching and experimenting  I came up with this bash script   if      timeout 20s COMMAND YOU WANT TO EXECUTE      timeout 20s AS MANY COMMANDS AS YOU WANT  then     echo  OK    if you want a positive response else     echo  Not OK       AND ALTERNATIVE COMMANDS fi

User · Answer

Building on  loup s answer     If you want to timeout a process and silence the kill job pid output  run      sleep 1  amp  amp  killall program 2 gt  dev null   amp    amp  amp  program --version    This puts the backgrounded process into a subshell so you don t see the job output

User · Answer

OS X doesn t use bash 4 yet  nor does it have  usr bin timeout  so here s a function that works on OS X without home-brew or macports that is similar to  usr bin timeout  based on Tino s answer    Parameter validation  help  usage  and support for other signals are an exercise for reader     implement  usr bin timeout only if it doesn t exist   -n    type -p timeout 2 gt  amp 1        function timeout         set -m  b     sleep   1   amp      SPID                2    RETVAL     kill   SPID   exit  RETVAL   amp      CPID          wait  1     SLEEPRETVAL        if    SLEEPRETVAL -eq 0    amp  amp  kill   CPID   gt  dev null 2 gt  amp 1   then       RETVAL 124         When you need to make sure it dies         sleep 1  kill -9   CPID   gt  dev null 2 gt  amp 1  amp        wait  2     else       wait  2       RETVAL        fi     return  RETVAL

User · Answer

Here is a version that does not rely on spawning a child process - I needed a standalone script which embedded this functionality  It also does a fractional poll interval  so you can poll quicker  timeout would have been preferred - but I m stuck on an old server    wait on command  lt timeout gt   lt poll interval gt  command wait on command         local timeout  1  shift     local interval  1  shift         amp      local child         loops   bc  lt  lt  lt     timeout    1    interval     0 5    sed  s       g         t   loops       while   t  gt  0    do         sleep  interval         kill -0  child  amp  gt  dev null    return           t -  1       done      kill  child  amp  gt  dev null    kill -0  child  amp  gt  dev null    return     sleep  interval     kill -9  child  amp  gt  dev null     echo Timed out    slow command         sleep 2     echo Completed normally      wait 1 sec in 0 1 sec increments wait on command 1 0 1 slow command    or call an external command wait on command 1 0 1 sleep 10

User · Answer

I prefer  timelimit   which has a package at least in debian   http   devel ringlet net sysutils timelimit   It is a bit nicer than the coreutils  timeout  because it prints something when killing the process  and it also sends SIGKILL after some time by default

User · Answer

My problem was maybe a bit different   I start a command via ssh on a remote machine and want to kill the shell and childs if the command hangs   I now use the following    ssh server    sleep 60  amp  amp  kill -9 0   2 gt  dev null  amp  my command  RC      sleep 1   pkill -P      exit  RC    This way the command returns 255 when there was a timeout or the returncode of the command in case of success  Please note that killing processes from a ssh session is handled different from an interactive shell  But you can also use the -t option to ssh to allocate a pseudo terminal  so it acts like an interactive shell

User · Answer

If you already know the name of the program  let s assume program  to terminate after the timeout  as an example 3 seconds   I can contribute a simple and somewhat dirty alternative solution    sleep 3  amp  amp  killall program   amp    program   This works perfectly if I call benchmark processes with system calls

User · Answer

Simple script with code clarity  Save to  usr local bin run      bin bash    run   Run command with timeout  1 seconds     Timeout seconds timeout seconds   1  shift    PID pid       Start timeout     sleep   timeout seconds    echo  Timed out after  timeout seconds seconds    kill -- - pid  amp  gt  dev null    amp  timeout pid       Run         Stop timeout kill  timeout pid  amp  gt  dev null   Times out a command that runs too long     run 2 sleep 10 Timed out after 2 seconds Terminated     Ends immediately for a command that completes     run 10 sleep 2

User · Answer

There you go   timeout --signal SIGINT 10  path to slow command with options   you may change the SIGINT and 10 as you desire

User · Answer

bin bash timeout 10 interval 1 delay 3         t   timeout             while   t  gt  0    do         echo   t          sleep  interval           Check if the process still exists          kill -0    2 gt   dev null    exit 0           t -  interval            done        Be nice  post SIGTERM first        echo SIGTERM to      kill -s TERM      sleep  delay   kill -0    2 gt   dev null  amp  amp    echo SIGKILL to      kill -s KILL               amp   exec

User · Answer

I was presented with a problem to preserve the shell context and allow timeouts  the only problem with it is it will stop script execution on the timeout - but it s fine with the needs I was presented      usr bin env bash  safe kill       ps aux   grep -v grep   grep  1  gt  dev null  amp  amp  kill   2 -   1    my timeout       typeset  my timeout  waiter pid  return    my timeout  1   echo  Timeout   my timeout  running        shift         trap  return 0  USR1     sleep   my timeout     echo  Timeout   my timeout  reached for          safe kill         amp     waiter pid               return      safe kill   waiter pid -USR1   echo  Timeout   my timeout  ran        return    return -0     my timeout 3 cd scripts my timeout 3 pwd my timeout 3 true   amp  amp  echo true    echo false my timeout 3 false  amp  amp  echo true    echo false my timeout 3 sleep 10 my timeout 3 pwd   with the outputs   Timeout 3  running  3 cd scripts Timeout 3  ran  cd scripts Timeout 3  running  3 pwd  home mpapis projects rvm rvm scripts Timeout 3  ran  pwd Timeout 3  running  3 true Timeout 3  ran  true true Timeout 3  running  3 false Timeout 3  ran  false false Timeout 3  running  3 sleep 10 Timeout 3  reached for  sleep 10 Terminated   of course I assume there was a dir called scripts

User · Answer

To timeout the slowcommand after 1 second   timeout 1 slowcommand    echo  I failed  perhaps due to time out   To determine whether the command timed out or failed for its own reasons  check whether the status code is 124     ping for 3 seconds  but timeout after only 1 second timeout 1 ping 8 8 8 8 -w3 EXIT STATUS    if    EXIT STATUS -eq 124   then echo  Process Timed Out   else echo  Process did not timeout  Something else went wrong   fi exit  EXIT STATUS   Note that when the exit status is 124  you don t know whether it timed out due to your timeout command  or whether the command itself terminated due to some internal timeout logic of its own and then returned 124  You can safely assume in either case  though  that a timeout of some kind happened

User · Answer

A very simplistic way     command  amp  sleep 5  pkill -9 -x -f  command    with pkill  option -f  you can kill your specific command with arguments or specify -n to avoid kill old process

User · Answer

In 99  of the cases the answer is NOT to implement any timeout logic   Timeout logic is in nearly any situation a red warning sign that something else is wrong and should be fixed instead   Is your process hanging or breaking after n seconds sometimes   Then find out why and fix that instead   As an aside  to do strager s solution right  you need to use wait   SPID  instead of fg 1  since in scripts you don t have job control  and trying to turn it on is stupid    Moreover  fg 1 relies on the fact that you didn t start any other jobs previously in the script which is a bad assumption to make

User · Answer

I have a cron job that calls a php script and  some times  it get stuck on php script  This solution was perfect to me    I use    scripttimeout -t 60  script php

[bash] Timeout a command in bash without unnecessary delay

Examples:

Examples related to bash

Examples related to command-line

Examples related to timeout

Examples related to utilities