I want to get output of a command/script to a variable but the process is triggered to run in background. I tried as below and few servers ran it correctly and I got the response. But in few I am getting i_res as empty.
I am trying to run it in background as the command has chance to get in hang state and I don't want to hung the parent script.
Hope I will get a response soon.
#!/bin/ksh
x_cmd="ls -l"
i_res=$(eval $x_cmd 2>&1 &)
k_pid=$(pgrep -P $$ | head -1)
sleep 5
c_errm="$(kill -0 $k_pid 2>&1 )"; c_prs=$?
if [ $c_prs -eq 0 ]; then
c_errm=$(kill -9 $k_pid)
fi
wait $k_pid
echo "Result : $i_res"
Try something like this:
#!/bin/ksh
pid=$$ # parent process
(sleep 5 && kill $pid) & # this will sleep and wake up after 5 seconds
# and kill off the parent.
termpid=$! # remember the timebomb pid
# put the command that can hang here
result=$( ls -l )
# if we got here in less than 5 five seconds:
kill $termpid # kill off the timebomb
echo "$result" # disply result
exit 0
Add whatever messages you need to the code. On average this will complete much faster than always having a sleep statement. You can see what it does by making the command sleep 6 instead of ls -l
Related
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[ $(( i = ++i % 4 )) ]}"
done
}
} 3>&1
I have a bash script that launches a child process that crashes (actually, hangs) from time to time and with no apparent reason (closed source, so there isn't much I can do about it). As a result, I would like to be able to launch this process for a given amount of time, and kill it if it did not return successfully after a given amount of time.
Is there a simple and robust way to achieve that using bash?
P.S.: tell me if this question is better suited to serverfault or superuser.
(As seen in:
BASH FAQ entry #68: "How do I run a command, and have it abort (timeout) after N seconds?")
If you don't mind downloading something, use timeout (sudo apt-get install timeout) and use it like: (most Systems have it already installed otherwise use sudo apt-get install coreutils)
timeout 10 ping www.goooooogle.com
If you don't want to download something, do what timeout does internally:
( cmdpid=$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'
The following script works as expected when executed from an Applescript do shell script command.
#!/bin/sh
sleep 10 &
#echo "hello world" > /tmp/apipe &
cpid=$!
sleep 1
if ps -ef | grep $cpid | grep sleep | grep -qv grep ; then
echo "killing blocking cmd..."
kill -KILL $cpid
# non zero status to inform launch script of problem...
exit 1
fi
But, if the sleep command (line 2) is swaped to the echo command in (line 3) together with the if statement, the script blocks when run from Applescript but runs fine from the terminal command line.
Any ideas?
EDIT: I should have mentioned that the script works properly when a consumer/reader is connected to the pipe. It only block when nothing is reading from the pipe...
OK, the following will do the trick. It basically kills the job using its jobid. Since there is only one, it's the current job %%.
I was lucky that I came across the this answer or it would have driven me crazy :)
#!/bin/sh
echo $1 > $2 &
sleep 1
# Following is necessary. Seems to need it or
# job will not complete! Also seen at
# https://stackoverflow.com/a/10736613/348694
echo "Checking for running jobs..."
jobs
kill %% >/dev/null 2>&1
if [ $? -eq 0 ] ; then
echo "Taking too long. Killed..."
exit 1
fi
exit 0
I have a python script called hdsr_writer.py. I can launch this script in shell by calling
"python hdsr_writer.py 1234"
where 1234 is a parameter.
I made a shell script to increase the number and execute the python script with the number every 1 second
for param from 1 to 100000
python hdsr_writer.py $param &
sleep (1)
Usually, the python script executes its task within 0.5 second. However, there are times at which the python script gets stuck and resides in the system for longer than 30 seconds. I don't want that. So I would like to monitor life time of each python process executed. If it has stayed for longer than 2 second it would be killed and re-executed 2 times at most.
Note: I would like do this in the shell script not python script because I could not change the python script.
Update: More explainations about my question
Please note that: launching a new python process and monitoring python processes are independent jobs. Launching job doesn't care how many python processes are running and how "old" they are, just calls "python hdsr_writer.py $param &" every 1 second after increasing param. On the other hand, monitoring job periodically checks life time of all hdsr_writer python processes. If one has resided more than 2 second in memory, kills it, and re-runs it at most of 2 times.
Not so short answer
#/bin/bash
param=1
while [[ $param -lt 100000 ]]; do
echo "param=$param"
chances=3
while [[ $chances -gt 0 ]]; do
python tst.py $param &
sleep 2
if [[ "$(jobs | grep 'Running')" == "" ]]; then
chances=0
else
kill -9 $(jobs -l | awk '{print $2}')
chances=$(($chances-1))
if [[ $chances -gt 0 ]]; then
echo "one more chance for parameter $param"
fi
fi
done
param=$(($param+1))
done
UPD
This is another answer as requested by OP.
Here is still 2 scripts in one. But they can be spitted in two files.
Please pay attention that $() & is used to run sub-shells in background
#!/bin/bash
# Script launcher
pscript='rand.py'
for param in {1..10}
do
# start background sub-shell, where python with $param is started
echo $(
left=3
error_on_exit=1
# go if any chances left and previous run exits not with code 0
while [[ ( ( $left -gt 0 ) && ( $error_on_exit -ne 0 ) ) ]]; do
left=$(($left-1))
echo "param=$param; chances left $left "
# run python and grab python exit code (=0 if ok)
python $pscript $param
error_on_exit=$?
done
) &
done
# Script controller
# just kills python processes older than 2 seconds
# exits after no python left
# $(...) & can be removed if this code goes to separate script
$(while [[ $(ps | grep -v 'grep' | grep -c python ) != "0" ]]
do
sleep 0.5
killall -9 -q --older-than 2s python
done) &
Use a combination of sleep and nohup commands. After sleep time use kill to finish the execution of python script. You can check if the process is running with ps command.
#!/usr/bin/ksh
for param from {1..100000}
nohup python hdsr_writer.py $param &
pid=$!
sleep(2)
if [ ps -p $pid ]
then
kill -9 $pid
fi
done
Re-answer:
I'd use two scripts, the first one (script1.ksh):
#!/usr/bin/ksh
for param from {1..1000000}
nohup script2.sh $param &
done
And the second (script2.ksh):
#!/usr/bin/ksh
for i from {1..3}
python hsdr_write.py $1 &
pid=$!
sleep(2)
if [ ps -p $pid ]
then
kill -9 $pid
else
echo 'Finalizado'$1 >> log.txt
return
fi
done
The first script will launch all yours processes one after the other. The second one will check his own python process.
I have a main script which run all the scripts in a folder.
#!/bin/bash
for each in /some_folder/*.sh
do
bash $each
done;
I want to know if execution of one of them lasts too long (more than N seconds). For example execution of script such as:
#!/bin/bash
ping -c 10000 google.com
will lasts very long, and I want my main script to e-mail me after N second.
All I can do now is to run all scripts with #timeout N option but it stops them!
Is it possible to E-mail me and not to stop execution of script?
Try this :
#!/bin/bash
# max seconds before mail alert
MAX_SECONDS=3600
# running the command in the background and get the pid
command_that_takes_a_long_time & _pid=$!
sleep $MAX_SECONDS
# if the pid is alive...
if kill &>/dev/null -0 $_pid; then
mail -s "script $0 takes more than $MAX_SECONDS" user#domain.tld < /dev/null
fi
We run the command in the background, then sleep for MAX_SECONDS in // and alert by email if the process takes more than what is permitted.
Finally, with your specific requirements :
#!/bin/bash
MAX_SECONDS=3600
alerter(){
bash "$1" & _pid=$!
sleep $MAX_SECONDS
if kill &>/dev/null -0 $_pid; then
mail -s "$2 takes more than $MAX_SECONDS" user#domain.tld < /dev/null
fi
}
for each in /some_folder/*.sh; do
alerter "$each" &
wait $_pid # remove this line if you wou'd like to run all scripts in //
done
You can do something like this:
( sleep 10 ; echo 'Takes a while' | sendmail myself#example.com ) &
email_pid=$!
bash $each
kill $email_pid
The first command is run in a subshell in the background. It first sleeps a while, then sends email. If the script $each finishes before the sleep expires, the subshell is killed without sending email.