I'm creating a bash script in which whenever my apache exceeds a fixed amount of numbers then it restart itself on next cronjob. I've created something but it is not running properly.
#!/bin/bash
RESTART="systemctl restart httpd"
COUNT="ps aux | grep httpd | wc -l"
SERVICE="httpd"
LOGFILE="/opt/httpd/autostart-apache2.log"
if COUNT > 45
then
echo "starting apache at $(date)" >> $LOGFILE
$RESTART >> $LOGFILE
else
echo "apache is running at $(date)"
fi
The error it is throwing is
line 10: COUNT: command not found
apache is running at Sat Sep 10 23:34:30 IST 2022
Can anyone help me on how to store the value of the output of ps aux | grep httpd | wc -l as a number and compare it with another number.
RESTART="systemctl restart httpd" is a variable assignment, although it might work for your use case, you should really use a function instead. See the Complex page for more info.
COUNT="ps aux | grep httpd | wc -l" is a variable assignment as well use Command Substitution, like what you did with $(date), on a side note grep has the -c option, there is no need for wc.
COUNT > 45 You're executing the COUNT word/string but since there is nothing in your script/path/function/executable with the same name (COUNT is a variable name in your script), thus you get the error: line 10: COUNT: command not found
> is a form of redirection if not used in Arithmetic Expression., it truncates a file or create it if it does not exists. Like in your code > 45 created a file named 45. Open the file for writing is the proper term word for it according to the bash manual.
Here is how I would write it.
#!/usr/bin/env bash
service="httpd"
count="$(ps aux | grep -c "$service")"
logfile="/opt/httpd/autostart-apache2.log"
restart(){ systemctl restart "$service" ; }
if (( count > 45 )); then
echo "starting apache at $(date)" >> "$logfile"
restart >> "$logfile" 2>&1
else
echo "apache is running at $(date)"
fi
(( count > 45 )) is a form of test in bash for comparing/testing numbers. The $ can be omitted inside it.
Related
I can't find how to structure my while loop properly to log to a text file all crashes of a given Linux application. I would like to get a prompt so I can input the application name and then a loop to watch the pid of the application. If the pid is null I wanted to log the timestamp in a text file and continue the loop. If still in null at the second iteration, don't log anything, keep monitoring until there are other crashes and other logs... and so on until the script stops with CTRL+C.
I've tried multiple variations of this script without luck. I think I need tips on how to think of a "loop structure" to achieve whatever goals...
read -p "What is the name of the application you want to monitor?" appname
pidofapp=`ps -elf | grep "$appname" | grep -v grep | awk '{print $4}'`
pidofappcheck=`ps -elf | grep "$appname" | grep -v grep | awk '{print $4}'`
while :
do
if [[ ! -z "$pidofappcheck" ]] ; then
pidwasnull=true
pidofappcheck=`ps -elf | grep "$appname" | grep -v grep | awk '{print $4}'`
if [[ "$pidofapp" == "$pidofappcheck" ]] ; then
printf "Still monitoring...\n"
sleep 5
elif [[ "$pidwasnull" == true ]] ; then
continue
fi
echo "FAILURE: Crash occurred at: "$(date)" - Crashes will be logged in the monitoring tool directory under results.txt"
date >> ./results.txt
fi
done
As it is right now, the script will echo:
What is the name of the application you want to monitor?running
Still monitoring...
FAILURE: Crash occurred at: Wed May 22 01:44:53 EDT 2019 - Crashes will be logged in the monitoring tool directory under results.txt
Still monitoring...
FAILURE: Crash occurred at: Wed May 22 01:44:58 EDT 2019 - Crashes will be logged in the monitoring tool directory under results.txt
Thanks in advance for any help.
Try something like this
#!/bin/bash
getpidofapp() {
# pid=$(ps -elf | grep "$1" | grep -v grep | awk '{print $4}' | head -1)
pid=$(pgrep "$1" | head -1)
test -n "${pid}" || { echo "Is ${appname} running?"; exit 1; }
}
read -rp "What is the name of the application you want to monitor?" appname
app_pid=$(getpidofapp "${appname}")
while : ; do
lastpid=$(getpidofapp "${appname}")
if [[ "${app_pid}" == "${lastpid}" ]] ; then
printf "Still monitoring...\n"
else
crashtxt="Crashes will be logged in the monitoring tool directory under results.txt"
echo "FAILURE: Crash occurred at: $(date) ${crashtxt}"
date >> ./results.txt
fi
sleep 5
done
So I have been able to find a solution based on what #Walter A wrote. Here is what I've used. It's working as expected so far.
#!/bin/bash
read -rp "What is the name of the application you want to monitor?" appname
app_pid=$(pidof "$appname")
#echo "First PID of "$appname" is "$app_pid""
while : ; do
lastpid=$(pidof "$appname")
if [[ "${app_pid}" == "${lastpid}" ]] ; then
printf "Still monitoring...\n"
else
crashtxt="Crashes will be logged in the monitoring tool directory under results.txt"
echo "FAILURE: Crash occurred at: $(date) ${crashtxt}"
date >> ./results.txt
app_pid="$lastpid"
fi
sleep 5
done
So this script will basically check the PID of the given app until you CTRL+C. If the PID of the app changes while the script is running. It will output the timestamps of when it occurred in a "results.txt" file and it will keep checking it until you press CTRL+C. Therefore I am going to use this to log all crash occurrences of my apps. Thanks a lot #Walter A
I am trying to write a small shell script, make it go to sleep for some amount of time like 20 seconds and then run it. Now if i open another terminal and try to run the same script, it shouldn't run as the process is running else where. How do I do it?
I know i should write something, make it go to sleep captures its pid and write a condition that if this pis is running somewhere then don't let it run anywhere. but how do i do it? Please give a code.
echo "this is a process"
sleep 60
testfilepid = `ps ax | grep test1.sh | grep -v grep | tr -s " " | cut -f1 -d " "| tail -1`
echo $testfilepid
if [[ $tesfilepid = " " ]]
sh test1.sh
else
echo "this process is already running"
fi
This is what I tried. when i execute this in 2 windows, both the windows give me the output this is a process.
You could use pgrep to check that your script/process is running, and negate the output, this is a very basic example that could give you an idea:
if ! pgrep -f sleep >/dev/null; then echo "will sleep" && sleep 3; fi
Notice the !, pgrep -f sleep will search for a process matching against full argument lists. (you could customize this to your needs). so if nothing matches your pattern then your script will be called.
I wanted to write a shell script for the following:
I want to check if a service is running, if it is running then exit 1, or else after 5 min of it not running, exit -1.
something like:
while(for 5 minutes) {
if service running, exit 1
}
exit -1 //service is not running even after 5 minutes, so exit -1.
I am able to check the condition that if service is running or not, but not able to add the time constraint part.
This is what i attempted
if (( $(ps -ef | grep -v grep | grep tomcat7 | wc -l) > 0 ));
then
echo "running"
else
echo "NOT running"
fi
You should use the bash sleep command. An excerpt from the man page:-
You could provide sleep 5m in your script to wait for 5 minutes and do an action.
NAME
sleep - delay for a specified amount of time
DESCRIPTION
Pause for NUMBER seconds. SUFFIX may be 's' for seconds (the default), 'm' for minutes, 'h' for hours or 'd' for days. Unlike most implementations that require NUMBER be an
integer, here NUMBER may be an arbitrary floating point number. Given two or more arguments, pause for the amount of time specified by the sum of their values.
A proper way to your solution would be:-
#!/bin/bash
maxAttempts=0
maxCounter=2 # Number of attempts can be controlled by this variable
while [ "$maxAttempts" -lt "$maxCounter" ]; do
if ps -ef | grep -v grep | grep "tomcat7" > /dev/null
then
echo "tomcat7 service running, "
exit 1
else
maxAttempts=$((maxAttempts+1))
sleep 5m # The script waits for 5 minutes before exiting with error code '-1'
fi
done
exit -1
The if condition works when the ps -ef | grep -v grep | grep "tomcat7" returns a command success error code for which the condition passes. > /dev/null to suppress all standard outpur(stdout, stderr) to /dev/null so that we can work only with the exit codes of the command provided.
I am using a bash script that calls multiple processes which have to start up in a particular order, and certain actions have to be completed (they then print out certain messages to the logs) before the next one can be started. The bash script has the following code which works really well for most cases:
tail -Fn +1 "$log_file" | while read line; do
if echo "$line" | grep -qEi "$search_text"; then
echo "[INFO] $process_name process started up successfully"
pkill -9 -P $$ tail
return 0
elif echo "$line" | grep -qEi '^error\b'; then
echo "[INFO] ERROR or Exception is thrown listed below. $process_name process startup aborted"
echo " ($line) "
echo "[INFO] Please check $process_name process log file=$log_file for problems"
pkill -9 -P $$ tail
return 1
fi
done
However, when we set the processes to print logging in DEBUG mode, they print so much logging that this script cannot keep up, and it takes about 15 minutes after the process is complete for the bash script to catch up. Is there a way of optimizing this, like changing 'while read line' to 'while read 100 lines', or something like that?
How about not forking up to two grep processes per log line?
tail -Fn +1 "$log_file" | grep -Ei "$search_text|^error\b" | while read line; do
So one long running grep process shall do preprocessing if you will.
Edit: As noted in the comments, it is safer to add --line-buffered to the grep invocation.
Some tips relevant for this script:
Checking that the service is doing its job is a much better check for daemon startup than looking at the log output
You can use grep ... <<<"$line" to execute fewer echos.
You can use tail -f | grep -q ... to avoid the while loop by stopping as soon as there's a matching line.
If you can avoid -i on grep it might be significantly faster to process the input.
Thou shalt not kill -9.
I'm trying to have a lightweight memory profiler for the matlab jobs that are run on my machine. There is either one or zero matlab job instance, but its process id changes frequently (since it is actually called by another script).
So here is the bash script that I put together to log memory usage:
#!/bin/bash
pid=`ps aux | grep '[M]ATLAB' | awk '{print $2}'`
if [[ -n $pid ]]
then
\grep VmSize /proc/$pid/status
else
echo "no pid"
fi
when I run this script in bash like this:
./script.sh
it works fine, giving me the following result:
VmSize: 1289004 kB
which is exactly what I want.
Now, I want to run this periodically. So I run it with watch, like this:
watch ./script.sh
But in this case I only receive:
no pid
Please note that I know the matlab job is still running, because I can see it with the same pid on top, and besides, I know each matlab job take several hours to finish.
I'm pretty sure that something is wrong with the quotes I have when setting pid. I just can't figure out how to fix it. Anyone knows what I'm doing wrong?
PS.
In the man page of watch, it says that commands are executed by sh -c. I did run my script like sh -c ./script and it works just fine, but watch doesn't.
Why don't you use a loop with sleep command instead?
For example:
#!/bin/bash
pid=`ps aux | grep '[M]ATLAB' | awk '{print $2}'`
while [ "1" ]
do
if [[ -n $pid ]]
then
\grep VmSize /proc/$pid/status
else
echo "no pid"
fi
sleep 10
done
Here the script sleeps(waits) for 10 seconds. You can set the interval you need changing the sleep command. For example to make the script sleep for an hour use sleep 1h.
To exit the script press Ctrl - C
This
pid=`ps aux | grep '[M]ATLAB' | awk '{print $2}'`
could be changed to:
pid=$(pidof MATLAB)
I have no idea why it's not working in watch but you could use a cron job and make the script log to a file like so:
#!/bin/bash
pid=$(pidof MATLAB) # Just to follow previously given advice :)
if [[ -n $pid ]]
then
echo "$(date): $(\grep VmSize /proc/$pid/status)" >> logfile
else
echo "$(date): no pid" >> logfile
fi
You'd of course have to create logfile with touch.
You might try just running ps command in watch. I have had issues in the past with watch chopping lines and such when they get too long.
It can be fixed by making the terminal you are running the command from wider or changing the column like this (may need to adjust the 160 to your liking):
export COLUMNS=160;