TL:DR
Check if a given PID is running, if yes kill the process.
count=0
while [[ "$count" -le 3 && ps -p $pid > /dev/null ]];
do
kill -9 $pid
count=$(( $count + 1 )):
done
To this I am getting an error as:
line 8: [: -p: binary operator expected
I am aware there are several similar questions, I already tried their solutions but it doesn't seem to work.
The while loop is logically incorrect, as #kvantour mentioned. Here is the script. Note that it will let you know if it could not kill the process, so you can investigate the root cause. The script gets PID as its first argument (e.g. $./kill-pid.sh 1234) Note that this works for bash ver. 4.1+:
#!/usr/bin/env bash
if ps -p $1 > /dev/null
then
output=$(kill -9 $1 2>&1)
if [ $? -ne 0 ]
then
echo "Process $1 cannot be killed. Reason:"
echo "$output"
# This line is added per OP request, to try to re-run the kill command if it failed for the first time.
# kill -9 $1
fi
fi
Related
I'm basically trying to make debugging easier for other scripts of mine.
(Centos 7.6)
What I need is a script doing :
tail -f the last file entry in a directory
if a new file appears in this directory, it logs this new file, smoothly
if I send a SIGINT (Ctrl+C), it doesn't leave orphans
with the less possible add-ons for the maximum portability
This is my non working solution :
CURRENT_FILE=`ls -1t | head -n1`
tail -n 100 -f "$CURRENT_FILE" &
PID=$!
while [ true ];
do
#is there a new file in the directory ?
NEW_FILE=`ls -1t | head -n1`
if [[ "$CURRENT_FILE" != "$NEW_FILE" ]]; then
#yes, so kill last tail
kill -9 $PID
clear
#tail on the new file
CURRENT_FILE=$NEW_FILE
tail -n 100 -f "$CURRENT_FILE"
PID=$!
fi
sleep 1s
done
The problem with this solution is that when I'm sending SIGINT (Ctrl+C), what I normally do when exiting a "tail -f", it leaves an orphan child in the background.
I've searched solution with "trap" but I don't get it well, and it doesn't seem to work with an eternal process like "tail -f".
I'll be glad to here your thoughts about that and get into advanced bash programming.
You can trap whenever the script exits and kill the process then. You don't need -9 to kill your tail though, that's overkill.
You can also use inotify to tell you when something happens in the directory instead of sleeping and rechecking. Here's a basic building block. inotify has a lot of events you can wait for. You can add detection if the file was moved/renamed so you don't have to restart the tail in those cases etc.
#!/bin/bash
killpid() {
if [[ -n $PID ]]; then
kill $PID
PID=""
fi
}
trap killpid EXIT
DIR="."
CURRENT_FILE="$(ls -1t "$DIR" | head -n1)"
tailit() {
echo "::: $CURRENT_FILE :::"
tail -n 100 -f "$CURRENT_FILE" &
PID=$!
}
tailit
# wait for any file to be created, modified or deleted
while EVENT=$(inotifywait -q -e create,modify,delete "$DIR"); do
# extract event
ev=$(sed -E "s/^${DIR}\/ (\S+) .+$/\1/" <<< "$EVENT")
# extract the affected file
NEW_FILE=${EVENT#${DIR}/ $ev }
case $ev in
MODIFY)
# start tailing the file if we aren't tailing it already
if [[ $NEW_FILE != $CURRENT_FILE ]]; then
killpid
CURRENT_FILE="$NEW_FILE"
tailit
fi
;;
CREATE)
# a new file, tail it
killpid
CURRENT_FILE="$NEW_FILE"
tailit
;;
DELETE)
# stop tailing if the file we are tailing was deleted
if [[ $NEW_FILE == $CURRENT_FILE ]]; then
echo "::: $CURRENT_FILE removed :::"
CURRENT_FILE=""
killpid
fi
;;
esac
done
You can use trap solution at the beginning of your shell.
#! /bin/bash
trap ctrl_c INT
function ctrl_c() {
if [[ -n "$PID" ]]; then
kill -9 $PID
fi
exit 0
}
CURRENT_FILE=`ls -1t | head -n1`
tail -n 100 -f "$CURRENT_FILE" &
PID=$!
while [ true ];
do
#is there a new file in the directory ?
NEW_FILE=`ls -1t | head -n1`
if [[ "$CURRENT_FILE" != "$NEW_FILE" ]]; then
#yes, so kill last tail
kill -9 $PID
clear
#tail on the new file
CURRENT_FILE=$NEW_FILE
tail -n 100 -f "$CURRENT_FILE" &
PID=$!
fi
sleep 1s
done
I need to have a .sh file that will echo 0 if my python service is not running. I know that pgrep is the command I want to use, but I am getting errors using it.
if [ [ ! $(pgrep -f service.py) ] ]; then
echo 0
fi
Is what I found online, and I keep getting the error
./test_if_running.sh: line 3: syntax error near unexpected token `fi'
./test_if_running.sh: line 3: `fi;'
When I type
./test_if_running.sh
The issue in your code is the nested [ ... ]. Also, as #agc has noted, what we need to check here is the exit code of pgrep and not its output. So, the right way to write the if is:
if ! pgrep -f service.py &> /dev/null 2>&1; then
# service.py is not running
fi
This is a bit simple, but why not just print a NOT'd exit code, like so:
! pgrep -f service.py &> /dev/null ; echo $?
As a bonus it'll print 1 if the service is running.
I have a shell script that does a backup. I set this script in a cron but the problem is that the backup is heavy so it is possible to execute a second rsync before the first ends up.
I thought to launch rsync in a script and then get PID and write a file that script checks if the process exist or not (if this file exist or not).
If I put rsync in background I get the PID but I don't know how to know when rsync ends up but, if I set rsync (no background) I can't get PID before the process finish so I can't write a file whit PID.
I don't know what is the best way to "have rsync control" and know when it finish.
My script
#!/bin/bash
pidfile="/home/${USER}/.rsync_repository"
if [ -f $pidfile ];
then
echo "PID file exists " $(date +"%Y-%m-%d %H:%M:%S")
else
rsync -zrt --delete-before /repository/ /mnt/backup/repositorio/ < /dev/null &
echo $$ > $pidfile
# If I uncomment this 'rm' and rsync is running in background, the file is deleted so I can't "control" when rsync finish
# rm $pidfile
fi
Can anybody help me?!
Thanks in advance !! :)
# check to make sure script isn't still running
# if it's still running then exit this script
sScriptName="$(basename $0)"
if [ $(pidof -x ${sScriptName}| wc -w) -gt 2 ]; then
exit
fi
pidof finds the pid of a process
-x tells it to look for scripts too
${sScriptName} is just the name of the script...you can hardcode this
wc -w returns the word count by words
-gt 2 no more than one instance running (instance plus 1 for the pidof check)
if more than one instance running then exit script
Let me know if this works for you.
Test both for presence of pid file and status of the running process like this:
#!/bin/bash
pidfile="/home/${USER}/.rsync_repository"
is_running =0
if [ -f $pidfile ];
then
echo "PID file exists " $(date +"%Y-%m-%d %H:%M:%S")
previous_pid=`cat $pidfile`
is_running=`ps -ef | grep $previous_pid | wc -l`
fi
if [ $is_running -gt 0 ];
then
echo "Previous process didn't quit yet"
else
rsync -zrt --delete-before /repository/ /mnt/backup/repositorio/ < /dev/null &
echo $$ > $pidfile
fi
Hope this helps!!!
I have Linux centralize server – Linux 5.X.
In some cases on my Linux server the get_hosts.ksh script could be run from some other different hosts.
For example get_hosts.ksh could run on my Linux machine three or more times at the same time.
My question:
How to avoid running multiple instances of process/script?
A common solution for your problem on *nix systems is to check for a lock file existence.
Usually lock file contains current process PID.
This is an example ksh script:
#!/bin/ksh
pid="/var/run/get_hosts.pid"
trap "rm -f $pid" SIGSEGV
trap "rm -f $pid" SIGINT
if [ -e $pid ]; then
exit # pid file exists, another instance is running, so now we politely exit
else
echo $$ > $pid # pid file doesn't exit, create one and go on
fi
# your normal workflow here...
rm -f $pid # remove pid file just before exiting
exit
UPDATE: Answering to OP comment, I add handling program interruptions and segfaults with trap command.
The normal way of doing this is to write the process id into a file. The first thing the script does is check for the existence of the file, read the pid, check if a process with that pid exists, and for extra paranoia points, if that process actually runs the script. If yes, the script exits.
Here's a simple example. The process in question is a binary, and this script makes sure the binary runs only once. This is not exactly what you need, but you should be able to adapt this:
RUNNING=0
PIDFILE=$PATH_TO/var/run/example.pid
if [ -f $PIDFILE ]
then
PID=`cat $PIDFILE`
ps -eo pid | grep $PID >/dev/null 2>&1
if [ $? -eq 0 ]
then
RUNNING=1
fi
fi
if [ $RUNNING -ne 1 ]
then
run_binary
PID=$!
echo $PID > $PIDFILE
fi
This is not very elaborate but should get you on the right track.
You can use a pid file to keep track of when the process is running. At the top of the script, check for the existence of the pid file and if it doesn't exist, create it and run the script, otherwise return.
Some sample code can be seen in this answer to a similar question.
You might consider using the (optional) lockfile(1) command (provided by procmail package on Debian).
I have a lot of scripts, and using this below code for prevent multiple/simulate run:
PID="/var/scripts/PID.txt" # Temp file
if [ ! -f "$PID" ]; then
echo $$ > "$PID" # Print actual PID into a file
else
ps -p $(cat "$PID") > /dev/null && exit || echo $$ > "$PID"
fi
Building on wallenborn's answer I also added a "staleness" check just in case the PID lock file is beyond a certain expected age in seconds.
# prevent simultaneous executions within an hourish
pid_file="$HOME/.harness.pid"
max_stale_seconds=3600
if [ -f $pid_file ]; then
pid="$(cat "$pid_file")"
let age_in_seconds="$(date +%s) - $(date -r "$pid_file" +%s)"
if ps $pid >/dev/null && [ $age_in_seconds -lt $max_stale_seconds ]; then
exit 1
fi
fi
echo $$>"$pid_file"
trap "rm -f \"$pid_file\"" SIGSEGV
trap "rm -f \"$pid_file\"" SIGINT
This could be made "smarter" to kill off the other executions should the PID be valid but this would be dangerous. Consider a sudden power failure and reset situation where the PID file contains a number that may now reference a completely different process.
I'm made the following code to determine if a process is running:
#!/bin/bash
ps cax | grep 'Nginx' > /dev/null
if [ $? -eq 0 ]; then
echo "Process is running."
else
echo "Process is not running."
fi
I would like to use my code to check multiple processes and use a list as input (see below), but getting stuck in the foreach loop.
CHECK_PROCESS=nginx, mysql, etc
What is the correct way to use a foreach loop to check multiple processes?
If your system has pgrep installed, you'd better use it instead of the greping of the output of ps.
Regarding you're question, how to loop through a list of processes, you'd better use an array. A working example might be something along these lines:
(Remark: avoid capitalized variables, this is an awfully bad bash practice):
#!/bin/bash
# Define an array of processes to be checked.
# If properly quoted, these may contain spaces
check_process=( "nginx" "mysql" "etc" )
for p in "${check_process[#]}"; do
if pgrep "$p" > /dev/null; then
echo "Process \`$p' is running"
else
echo "Process \`$p' is not running"
fi
done
Cheers!
Use a separated list of of processes:
#!/bin/bash
PROC="nginx mysql ..."
for p in $PROC
do
ps cax | grep $p > /dev/null
if [ $? -eq 0 ]; then
echo "Process $p is running."
else
echo "Process $p is not running."
fi
done
If you simply want to see if either one of them is running, then you don't need loo. Just give the list to grep:
ps cax | grep -E "Nginx|mysql|etc" > /dev/null
Create file chkproc.sh
#!/bin/bash
for name in $#; do
echo -n "$name: "
pgrep $name > /dev/null && echo "running" || echo "not running"
done
And then run:
$ ./chkproc.sh nginx mysql etc
nginx: not running
mysql: running
etc: not running
Unless you have some old or "weird" system you should have pgrep available.