I'm running a shell test program that I can view a progress bar but when I run it I keep getting a unary error . Is kill -0 a way to kill a subprocess in shell ?
Or is there another method to test if my process has died?
heres my code to run a progress bar until my command ends:
#!/bin/sh
# test my progress bar
spin[0]="-"
spin[1]="\\"
spin[2]="|"
spin[3]="/"
sleep 10 2>/dev/null & # run as background process
pid=$! # grab process id
echo -n "[sleeping] ${spin[0]}"
while [ kill -0 $pid ] # wait for process to end
do
for i in "${spin[#]}"
do
echo -ne "\b$i"
sleep 0.1
done
done
enter code here
1. Is kill -0 a way to kill a subprocess in shell ?
On Linux OS, kill -0 is just a way to try to kill a process and see what happens, '0' is not a POSIX signal, it does nothing at all.
If the process is running, kill will return 0, if not, it will return 1.
ps $pid >/dev/null 2>&1 could do the same job.
To kill a process, one generally use the SIGQUIT/3 (quit program) or SIGKILL/9 (terminate program) ; the process could trap the signal and make a clean exit, or it could ignore the signal so the OS has to terminate it 'quick and dirty'.
2. test and '['
The square bracket '[' is an utility ( /bin/[ ), and expect something you didn't provide correctly.
The syntax of while is while list; do list; done where list will return an exit code, so you don't have to use something else.
3. how do I watch for a process to have died in shell script?
Like you did, the code below will do the job:
#!/bin/bash
spin[0]="-"
spin[1]="\\"
spin[2]="|"
spin[3]="/"
sleep 10 2>/dev/null & # run as background process
pid=$! # grab process id
echo -n "[sleeping] ${spin[0]}"
#while ps -p $pid >/dev/null 2>&1 # using ps
while kill -0 $pid >/dev/null 2>&1 # using kill
do
for i in "${spin[#]}"
do
echo -ne "\b$i"
sleep 0.5
done
done
CAVEATS
I use /bin/bash as interpreter, as some of the Bourne Shell (sh) could not support the use of an array (ie spin[n]).
It's probably cleaner to run the spinner in the background and kill it when the process (running in the foreground) terminates. Or, you could open another file descriptor and write something into it after the background process terminates, and have the main process block on a read. eg:
#!/bin/bash
# test my progress bar
spin[0]='-'
spin[1]='\'
spin[2]='|'
spin[3]='/'
{ { { sleep 10 2>/dev/null; echo >&5; } & # run as background process
} 5>&1 1>&3 | { # wait for process to end
while ! read -t 1; do
printf "\r[sleeping] ${spin[ $(( i = ++i % 4 )) ]}"
done
}
} 3>&1
I need to know an another process pid which is executed as a command in the bash script like a nmap scan etc as an when the process is created I can display a bar or a spinner
#!/bin/sh
G='\033[0;32m'
B='\033[0m'
${G}Enter IP TAIL LIKE 0.1 OR 1.1${B}"
read v
${G}ENTER Device NAME ${B}"
read k
nmap -A -Pn -sV 192.168.$v -oN /tmp/op
//here i want a while loop for displaying a spinner
edit code is updated Thts the code in case tht was not visible properly ^^
As the pid dies when its completed I can use it as a count or a flag or something similar to end the spinner.
I'm working on Kali nethunter.
P.S This is my first time on stack overflow pls forgive me if its too stupid or tell me if I missed something.
A starting point:
#!/bin/bash
echo "Enter IP:"
read -r ip
# `&` runs in parallel
# always quote variables
nmap "$ip" &
# `$!` get's the background process PID
pid=$!
...
# you can see if a pid is running by checking exit status of `kill -0`
while kill -0 "$pid" 2>&1 >/dev/null; do
printf ...
...
done
nmap -A -Pn -sV 192.168.0.1 -p -oN /tmp/op >/dev/null & pid=$!
i=1
sp="/-\|"
echo -n ' '
while kill -0 "$pid" 2>&1 >/dev/null;
do
printf "\b${sp:i++%${#sp}:1}"
done
*Problem solved thanks to * kamil cuk
I have a bash script that launches a child process that crashes (actually, hangs) from time to time and with no apparent reason (closed source, so there isn't much I can do about it). As a result, I would like to be able to launch this process for a given amount of time, and kill it if it did not return successfully after a given amount of time.
Is there a simple and robust way to achieve that using bash?
P.S.: tell me if this question is better suited to serverfault or superuser.
(As seen in:
BASH FAQ entry #68: "How do I run a command, and have it abort (timeout) after N seconds?")
If you don't mind downloading something, use timeout (sudo apt-get install timeout) and use it like: (most Systems have it already installed otherwise use sudo apt-get install coreutils)
timeout 10 ping www.goooooogle.com
If you don't want to download something, do what timeout does internally:
( cmdpid=$BASHPID; (sleep 10; kill $cmdpid) & exec ping www.goooooogle.com )
In case that you want to do a timeout for longer bash code, use the second option as such:
( cmdpid=$BASHPID;
(sleep 10; kill $cmdpid) \
& while ! ping -w 1 www.goooooogle.com
do
echo crap;
done )
# Spawn a child process:
(dosmth) & pid=$!
# in the background, sleep for 10 secs then kill that process
(sleep 10 && kill -9 $pid) &
or to get the exit codes as well:
# Spawn a child process:
(dosmth) & pid=$!
# in the background, sleep for 10 secs then kill that process
(sleep 10 && kill -9 $pid) & waiter=$!
# wait on our worker process and return the exitcode
exitcode=$(wait $pid && echo $?)
# kill the waiter subshell, if it still runs
kill -9 $waiter 2>/dev/null
# 0 if we killed the waiter, cause that means the process finished before the waiter
finished_gracefully=$?
sleep 999&
t=$!
sleep 10
kill $t
I also had this question and found two more things very useful:
The SECONDS variable in bash.
The command "pgrep".
So I use something like this on the command line (OSX 10.9):
ping www.goooooogle.com & PING_PID=$(pgrep 'ping'); SECONDS=0; while pgrep -q 'ping'; do sleep 0.2; if [ $SECONDS = 10 ]; then kill $PING_PID; fi; done
As this is a loop I included a "sleep 0.2" to keep the CPU cool. ;-)
(BTW: ping is a bad example anyway, you just would use the built-in "-t" (timeout) option.)
Assuming you have (or can easily make) a pid file for tracking the child's pid, you could then create a script that checks the modtime of the pid file and kills/respawns the process as needed. Then just put the script in crontab to run at approximately the period you need.
Let me know if you need more details. If that doesn't sound like it'd suit your needs, what about upstart?
One way is to run the program in a subshell, and communicate with the subshell through a named pipe with the read command. This way you can check the exit status of the process being run and communicate this back through the pipe.
Here's an example of timing out the yes command after 3 seconds. It gets the PID of the process using pgrep (possibly only works on Linux). There is also some problem with using a pipe in that a process opening a pipe for read will hang until it is also opened for write, and vice versa. So to prevent the read command hanging, I've "wedged" open the pipe for read with a background subshell. (Another way to prevent a freeze to open the pipe read-write, i.e. read -t 5 <>finished.pipe - however, that also may not work except with Linux.)
rm -f finished.pipe
mkfifo finished.pipe
{ yes >/dev/null; echo finished >finished.pipe ; } &
SUBSHELL=$!
# Get command PID
while : ; do
PID=$( pgrep -P $SUBSHELL yes )
test "$PID" = "" || break
sleep 1
done
# Open pipe for writing
{ exec 4>finished.pipe ; while : ; do sleep 1000; done } &
read -t 3 FINISHED <finished.pipe
if [ "$FINISHED" = finished ] ; then
echo 'Subprocess finished'
else
echo 'Subprocess timed out'
kill $PID
fi
rm finished.pipe
Here's an attempt which tries to avoid killing a process after it has already exited, which reduces the chance of killing another process with the same process ID (although it's probably impossible to avoid this kind of error completely).
run_with_timeout ()
{
t=$1
shift
echo "running \"$*\" with timeout $t"
(
# first, run process in background
(exec sh -c "$*") &
pid=$!
echo $pid
# the timeout shell
(sleep $t ; echo timeout) &
waiter=$!
echo $waiter
# finally, allow process to end naturally
wait $pid
echo $?
) \
| (read pid
read waiter
if test $waiter != timeout ; then
read status
else
status=timeout
fi
# if we timed out, kill the process
if test $status = timeout ; then
kill $pid
exit 99
else
# if the program exited normally, kill the waiting shell
kill $waiter
exit $status
fi
)
}
Use like run_with_timeout 3 sleep 10000, which runs sleep 10000 but ends it after 3 seconds.
This is like other answers which use a background timeout process to kill the child process after a delay. I think this is almost the same as Dan's extended answer (https://stackoverflow.com/a/5161274/1351983), except the timeout shell will not be killed if it has already ended.
After this program has ended, there will still be a few lingering "sleep" processes running, but they should be harmless.
This may be a better solution than my other answer because it does not use the non-portable shell feature read -t and does not use pgrep.
Here's the third answer I've submitted here. This one handles signal interrupts and cleans up background processes when SIGINT is received. It uses the $BASHPID and exec trick used in the top answer to get the PID of a process (in this case $$ in a sh invocation). It uses a FIFO to communicate with a subshell that is responsible for killing and cleanup. (This is like the pipe in my second answer, but having a named pipe means that the signal handler can write into it too.)
run_with_timeout ()
{
t=$1 ; shift
trap cleanup 2
F=$$.fifo ; rm -f $F ; mkfifo $F
# first, run main process in background
"$#" & pid=$!
# sleeper process to time out
( sh -c "echo \$\$ >$F ; exec sleep $t" ; echo timeout >$F ) &
read sleeper <$F
# control shell. read from fifo.
# final input is "finished". after that
# we clean up. we can get a timeout or a
# signal first.
( exec 0<$F
while : ; do
read input
case $input in
finished)
test $sleeper != 0 && kill $sleeper
rm -f $F
exit 0
;;
timeout)
test $pid != 0 && kill $pid
sleeper=0
;;
signal)
test $pid != 0 && kill $pid
;;
esac
done
) &
# wait for process to end
wait $pid
status=$?
echo finished >$F
return $status
}
cleanup ()
{
echo signal >$$.fifo
}
I've tried to avoid race conditions as far as I can. However, one source of error I couldn't remove is when the process ends near the same time as the timeout. For example, run_with_timeout 2 sleep 2 or run_with_timeout 0 sleep 0. For me, the latter gives an error:
timeout.sh: line 250: kill: (23248) - No such process
as it is trying to kill a process that has already exited by itself.
#Kill command after 10 seconds
timeout 10 command
#If you don't have timeout installed, this is almost the same:
sh -c '(sleep 10; kill "$$") & command'
#The same as above, with muted duplicate messages:
sh -c '(sleep 10; kill "$$" 2>/dev/null) & command'
I have a script which runs a long running process.
This process is currently stopped after a timeout.
#!/bin/bash
timeout 3600 ./longrunningprocess
My problem is now that this process does not return before the timeout is reached and sometimes I need to stop it earlier.
What do I need?
I want to start some other script in parallel which checks periodically if my longrunningprocess should stop. When this bash script returns, the timeout command should be killed.
Any idea how I could achieve that?
Is there anything like the timeout command? Not with a timespan but a script I could start and which is like the event trigger?
E.g.
#!/bin/bash
fancyCommandKillsSecondCommandIfFirstCommandReturns "./myPeriodicScript.sh" "timeout 3600 ./longrunningprocess"
Thanks!
Edit: Something like "Start 2 Processes in parallel and kill both if one returns" would also work...
Edit2: The answers gave me some ideas for a script:
#!/bin/bash
FirstProcess="${1}"
SecondProcess="${2}"
exec $FirstProcess &
PID1=$!
exec $SecondProcess &
PID2=$!
function killall {
if ps -p $PID1 > /dev/null
then
kill -9 $PID1
fi
if ps -p $PID2 > /dev/null
then
kill -9 $PID2
fi
}
trap killall EXIT
while true; do
if ! ps -p $PID1 > /dev/null
then
exit;
fi
if ! ps -p $PID2 > /dev/null
then
exit;
fi
sleep 5;
done
This kind of does what I want. Is there any native functionality or a better way to do this?
Start the longrunningprocess in the background and remember the pid.
#!/bin/bash
timeout 3600 ./longrunningprocess &
long_pid=$!
./myPeriodicScript.sh
kill -9 ${long_pid}
If you parse the output of the longrunningprocess to determine if the process needs to be killed, then you could do something like this:
#!/bin/bash
FIFO="tmpfifo"
TIMEOUT=10
mkfifo $FIFO
timeout 100 ./longrun &> $FIFO &
PID=$!
while read line; do
echo "Parsing $line see if $PID needs to be killed";
if [ "$line" = "5" ]; then
kill $PID
fi
done < $FIFO
exit
This will pipe all output into a FIFO and start reading from that fifo. In addition, it keeps the PID of the timeout process, so it can be killed.
I have wrote this script but when i run the job -ls and ps|grep i get no results here is my script:
#!/bin/bash
trap 'echo -e "kill Command given \n";exit 2'SIGINT SIGTERM
count=1
echo "start of the program"
while [ $count -le 10 ]
do
echo "Loop #${count}"
sleep 10
count=$[ count + 1 ]
done
echo "end of program"
This syntax is invalid:
trap 'echo -e "kill Command given \n";exit 2'SIGINT SIGTERM
because you don't have valid spacing. Use this instead:
trap 'echo -e "kill Command given \n"; exit 2' INT TERM
You're probably doing something else wrong, too, since this works fine for me:
# Start 10 sleep processes in the background.
for x in {1..10}; do
sleep 60 &
done
$ pgrep -c sleep
10
I'm getting the results I'm expecting, which is a count of the number of sleep processes currently running. If you're expecting something else, please update your question and provide some examples of your expected output.
I use this
ps | awk /$1/'{print $4; exit}'