bash script started through cron (root) not ending as expected
1
I have a script as follows, and I am trying to run it as a root cron job. The script starts mycommand, which in turn starts another process. When a condition is met, I would like the script to kill mycommand and its child process before exiting. Now, this seems to work at the terminal, the child processes end when the condition is met. But when the script is started as a root cron job, mycommand continues to run until I kill it manually. What am I doing wrong?
#!/bin/bash
# function to trap and clean exit
function clean_exit
{
PGID=`ps xao pgid,command,pid | grep 'mycommand'| sed 's/ .*//'`
kill -9 -$PGID
echo "process group killed: "$PGID
}
trap clean_exit SIGINT SIGTERM EXIT
sudo mycommand $1 > output.txt &
while sleep 1; do
# check output.txt every second
if [ condition met]; then
exit 1;
fi;
done
crontab line is as follows:
30 10 * * * bash path/to/myscript.sh
bash cron root
asked Jan 19 at 15:08
sraosrao
1062
add a comment |
1
I have a script as follows, and I am trying to run it as a root cron job. The script starts mycommand, which in turn starts another process. When a condition is met, I would like the script to kill mycommand and its child process before exiting. Now, this seems to work at the terminal, the child processes end when the condition is met. But when the script is started as a root cron job, mycommand continues to run until I kill it manually. What am I doing wrong?
#!/bin/bash
# function to trap and clean exit
function clean_exit
{
PGID=`ps xao pgid,command,pid | grep 'mycommand'| sed 's/ .*//'`
kill -9 -$PGID
echo "process group killed: "$PGID
}
trap clean_exit SIGINT SIGTERM EXIT
sudo mycommand $1 > output.txt &
while sleep 1; do
# check output.txt every second
if [ condition met]; then
exit 1;
fi;
done
crontab line is as follows:
30 10 * * * bash path/to/myscript.sh
bash cron root
asked Jan 19 at 15:08
sraosrao
1062
Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by usingexec, oreval $variable; and the test condition isif [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...
– pa4080
Jan 19 at 15:30
3
I'm curious how yourclean_exitfunction works at all - on my 16.04 system, all the lines fromps xao pgid,command,pidstart with a space - sosed 's/ .*//'returns a bunch of empty lines
– steeldriver
Jan 19 at 17:16
@steeldriver That's a good catch! It looks like pgids are right-aligned byps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed thatsedtoawk '{print $1}'and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.
– srao
Jan 19 at 20:44
1
Changegrep 'mycommand'togrep '[m]ycommand'to exclude thegrepprocess from the results.
– dessert
Jan 20 at 8:30
add a comment |
1
1
1
I have a script as follows, and I am trying to run it as a root cron job. The script starts mycommand, which in turn starts another process. When a condition is met, I would like the script to kill mycommand and its child process before exiting. Now, this seems to work at the terminal, the child processes end when the condition is met. But when the script is started as a root cron job, mycommand continues to run until I kill it manually. What am I doing wrong?
#!/bin/bash
# function to trap and clean exit
function clean_exit
{
PGID=`ps xao pgid,command,pid | grep 'mycommand'| sed 's/ .*//'`
kill -9 -$PGID
echo "process group killed: "$PGID
}
trap clean_exit SIGINT SIGTERM EXIT
sudo mycommand $1 > output.txt &
while sleep 1; do
# check output.txt every second
if [ condition met]; then
exit 1;
fi;
done
crontab line is as follows:
30 10 * * * bash path/to/myscript.sh
bash cron root
asked Jan 19 at 15:08
sraosrao
1062
I have a script as follows, and I am trying to run it as a root cron job. The script starts mycommand, which in turn starts another process. When a condition is met, I would like the script to kill mycommand and its child process before exiting. Now, this seems to work at the terminal, the child processes end when the condition is met. But when the script is started as a root cron job, mycommand continues to run until I kill it manually. What am I doing wrong?
#!/bin/bash
# function to trap and clean exit
function clean_exit
{
PGID=`ps xao pgid,command,pid | grep 'mycommand'| sed 's/ .*//'`
kill -9 -$PGID
echo "process group killed: "$PGID
}
trap clean_exit SIGINT SIGTERM EXIT
sudo mycommand $1 > output.txt &
while sleep 1; do
# check output.txt every second
if [ condition met]; then
exit 1;
fi;
done
crontab line is as follows:
30 10 * * * bash path/to/myscript.sh
bash cron root
bash cron root
asked Jan 19 at 15:08
sraosrao
1062
asked Jan 19 at 15:08
sraosrao
1062
asked Jan 19 at 15:08
sraosrao
1062
asked Jan 19 at 15:08
sraosrao
1062
asked Jan 19 at 15:08
sraosrao
1062
1062
Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by usingexec, oreval $variable; and the test condition isif [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...
– pa4080
Jan 19 at 15:30
3
I'm curious how yourclean_exitfunction works at all - on my 16.04 system, all the lines fromps xao pgid,command,pidstart with a space - sosed 's/ .*//'returns a bunch of empty lines
– steeldriver
Jan 19 at 17:16
@steeldriver That's a good catch! It looks like pgids are right-aligned byps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed thatsedtoawk '{print $1}'and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.
– srao
Jan 19 at 20:44
1
Changegrep 'mycommand'togrep '[m]ycommand'to exclude thegrepprocess from the results.
– dessert
Jan 20 at 8:30
add a comment |
Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by usingexec, oreval $variable; and the test condition isif [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...
– pa4080
Jan 19 at 15:30
3
I'm curious how yourclean_exitfunction works at all - on my 16.04 system, all the lines fromps xao pgid,command,pidstart with a space - sosed 's/ .*//'returns a bunch of empty lines
– steeldriver
Jan 19 at 17:16
@steeldriver That's a good catch! It looks like pgids are right-aligned byps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed thatsedtoawk '{print $1}'and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.
– srao
Jan 19 at 20:44
1
Changegrep 'mycommand'togrep '[m]ycommand'to exclude thegrepprocess from the results.
– dessert
Jan 20 at 8:30
Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by using
exec, or eval $variable; and the test condition is if [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...– pa4080
Jan 19 at 15:30
Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by using
exec, or eval $variable; and the test condition is if [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...– pa4080
Jan 19 at 15:30
3
3
I'm curious how your
clean_exit function works at all - on my 16.04 system, all the lines from ps xao pgid,command,pid start with a space - so sed 's/ .*//' returns a bunch of empty lines– steeldriver
Jan 19 at 17:16
I'm curious how your
clean_exit function works at all - on my 16.04 system, all the lines from ps xao pgid,command,pid start with a space - so sed 's/ .*//' returns a bunch of empty lines– steeldriver
Jan 19 at 17:16
@steeldriver That's a good catch! It looks like pgids are right-aligned by
ps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed that sed to awk '{print $1}' and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.– srao
Jan 19 at 20:44
@steeldriver That's a good catch! It looks like pgids are right-aligned by
ps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed that sed to awk '{print $1}' and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.– srao
Jan 19 at 20:44
1
1
Change
grep 'mycommand' to grep '[m]ycommand' to exclude the grep process from the results.– dessert
Jan 20 at 8:30
Change
grep 'mycommand' to grep '[m]ycommand' to exclude the grep process from the results.– dessert
Jan 20 at 8:30
add a comment |
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Hello, in this answer I've used similar approach, but the whole command is stored as value of variable and then it is executed by using
exec, oreval $variable; and the test condition isif [[ -z $(ps -aux | grep "$variable" | sed '$ d') ]]...– pa4080
Jan 19 at 15:30
3
I'm curious how your
clean_exitfunction works at all - on my 16.04 system, all the lines fromps xao pgid,command,pidstart with a space - sosed 's/ .*//'returns a bunch of empty lines– steeldriver
Jan 19 at 17:16
@steeldriver That's a good catch! It looks like pgids are right-aligned by
ps xao, so i didn't realise that pgids with fewer digits (e.g. 5000) than the higher pgids (e.g. 12345) have leading space(s). I have now changed thatsedtoawk '{print $1}'and it works as it should in crontab too. I didn't catch it at the terminal because the pgids didn't have leading spaces during testing. Could you post your comment as an answer please, so that I can accept it? Thanks.– srao
Jan 19 at 20:44
1
Change
grep 'mycommand'togrep '[m]ycommand'to exclude thegrepprocess from the results.– dessert
Jan 20 at 8:30