Hello I am new to shell script and I need to handle the error coming from a command being excuted inside echo like the following
echo -e "some internal command that I can't share \nq" | nc localhost 10000
I want to say
if [[ there's no error ]]
try
echo "YOUR SUPERSECRET COMMAND" | nc localhost 10000 | grep "Your expected error"
if [[ $? -eq 0 ]]; then
echo "Do something useful with error"
else
echo "Success"
fi
grep return 0 on matching and returns 1 when it doesn't find matching string.
The shell variable $? will give you the exit code. So, you could do:
echo -e "some internal command that I can't share \nq" | nc localhost 10000
rc=$?
if [[ $rc == 0 ]]; then
echo "success"
fi
Or simply,
if echo -e "some internal command that I can't share \nq" | nc localhost 10000; then
echo "success"
fi
Here is a concise way of doing it:
internalcommand &>/dev/null 2>&1 && echo OK || echo FAILED
If internalcommand succeeds OK will be printed to stdout, if it fails FAILED is printed.
Note tested on Bash v4
This question already has an answer here:
checking if grep command returns correct output
(1 answer)
Closed 7 years ago.
I have done a file named hosts.txt which includes some websites, to test the ping on each website with a script. What I want to do with my script is I want to loop through each line that includes different websites, and it should tell if the website is up or down (by measuring the ping command on each)
What my problem is that I don't really know how to get the return value of the ping command, so in case a website is up it should say "'website name' found" or not found. I have been researching, also tried out the ! command and different ways in the if-statement, but none of them seem to work.
My code:
#!/bin/bash
echo
echo "Monitoring hosts from file hosts.txt ..."
echo
echo
egrep -v '^(#|$)' hosts.txt | while read line; do #put the egrep value
#which is the lines in hosts.txt, and loop through each one of them
if [ ping $line ];then
echo "$line is up"
else
echo "$line is not up"
fi
done
echo
You need to use the $? special variable.
For example:
ping $line
pingResponse = $?
if [ $pingResponse -eq 0 ];then
echo "$line is up"
else
echo "$line is not up"
fi
you can test for boolean like:
[[ `ping $line` ]]
.
#!/bin/bash
echo
echo "Monitoring hosts from file hosts.txt ..."
echo
echo
egrep -v '^(#|$)' hosts.txt | while read line; do #put the egrep value
#which is the lines in hosts.txt, and loop through each one of them
if [[ `ping $line` ]];then
echo "$line is up"
else
echo "$line is not up"
fi
done
All I want from this script is to ssh to the host, and check if the process is alive, and if it is not, I want the littel script to die.
Does not die though. It stops, and then starts up again on the ssh is successful again.
I want death though.
#!/bin/bash
iterate=0
while [ $iterate -le 20000 ]
do
rc=$?
ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper "
if [[ $rc -eq 0 ]] ; then
sleep 2
iterate=$((iterate+1 ))
else
break
exit 1
fi
done
It will iterate to 2000, however if the remote process breaks, it will not die. It will not break and exit.
this will work - but won't sleep - if I put a sleep the rc goes to 0 and is never dies.
so this works but is too basic.
#!/bin/bash
set -e
while : ; do
ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper" > /dev/null 2>&1
done
You set rc=$? before the ssh command, and the last command was the test ([) command, which just succeeded, so when you test if [[ $rc -eq 0 ]] the answer is always 'yes, it does'.
It's best to test the status of ssh directly:
#!/bin/bash
iterate=0
while [ $iterate -le 20000 ]
do
if ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper"; then
sleep 2
((iterate++))
else
break # or exit 1
fi
done
I need help with replacing the following script with a different format where a configuration file, and a loop is used.
[FedoraC]$ cat script.sh
#!/bin/bash
grep -q /tmp /etc/fstab
if [ $? -eq 0 ]; then
echo "True"
else
echo "False"
fi
mount | grep ' /tmp' | grep nodev
if [ $? -eq 0 ]; then
echo "True"
else
echo "False"
fi
mount | grep /tmp | grep nosuid
if [ $? -eq 0 ]; then
echo "True"
else
echo "False"
fi
So far I have the following script which should take the values from a source/conf file and run each command found in the conf file one by one. After the command is executed the output would be "True" or "False"
conf file is formed by Unix commands: /opt/conf1
[FedoraC]$ cat conf1
grep -q /tmp /etc/fstab
mount | grep /tmp | grep nodev
mount | grep /tmp | grep nosuid
mount | grep /tmp | grep noexec
[FedoraC]$ cat new_script.sh
#!/bin/bash
. conf1
for i in $#;
do $i
if [ $i -eq 0 ]; then
echo "Passed"
else
echo "Failed"
fi
done
Instead of displaying the output based on the conditional statement, the script runs each line one by one from conf1, and not echo messages are seen.
Can I get some help please.
try this:
#! bin/bash
while read L; do
echo $L'; exit $?'|sh
if [ $? -eq 0 ]; then
echo Pass
else
echo Failed
fi
done < conf1
The more robust and canonical way to do this would be to have a directory /opt/conf1.d/, and put each of your lines as an executable script in this directory. You can then do
for file in /opt/conf1.d/*
do
[[ -x $file ]] || continue
if "$file"
then
echo "Passed"
else
echo "Failed"
fi
done
This has the advantages of supporting multi-line scripts, or scripts with more complex logic. It also lets you write the check script in any language, and lets scripts and packages add and remove contents easily and non-interactively.
If you really want to stick with your design, you can do it with:
while IFS= read -r line
do
if ( eval "$line" )
then
echo "Passed"
else
echo "Failed"
fi
done < /opt/conf1
The parentheses in the if statement runs eval in a subshell, so that lines can't interfere with each other by setting variables or exiting your entire loop.
This question already has answers here:
Linux Script to check if process is running and act on the result
(8 answers)
Closed 5 years ago.
I wrote a bash-script to check if a process is running. It doesn't work since the ps command always returns exit code 1. When I run the ps command from the command-line, the $? is correctly set, but within the script it is always 1. Any idea?
#!/bin/bash
SERVICE=$1
ps -a | grep -v grep | grep $1 > /dev/null
result=$?
echo "exit code: ${result}"
if [ "${result}" -eq "0" ] ; then
echo "`date`: $SERVICE service running, everything is fine"
else
echo "`date`: $SERVICE is not running"
fi
Bash version: GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
There are a few really simple methods:
pgrep procname && echo Running
pgrep procname || echo Not running
killall -q -0 procname && echo Running
pidof procname && echo Running
This trick works for me. Hope this could help you. Let's save the followings as checkRunningProcess.sh
#!/bin/bash
ps_out=`ps -ef | grep $1 | grep -v 'grep' | grep -v $0`
result=$(echo $ps_out | grep "$1")
if [[ "$result" != "" ]];then
echo "Running"
else
echo "Not Running"
fi
Make the checkRunningProcess.sh executable.And then use it.
Example to use.
20:10 $ checkRunningProcess.sh proxy.py
Running
20:12 $ checkRunningProcess.sh abcdef
Not Running
I tried your version on BASH version 3.2.29, worked fine. However, you could do something like the above suggested, an example here:
#!/bin/sh
SERVICE="$1"
RESULT=`ps -ef | grep $1 | grep -v 'grep' | grep -v $0`
result=$(echo $ps_out | grep "$1")
if [[ "$result" != "" ]];then
echo "Running"
else
echo "Not Running"
fi
I use this one to check every 10 seconds process is running and start if not and allows multiple arguments:
#!/bin/sh
PROCESS="$1"
PROCANDARGS=$*
while :
do
RESULT=`pgrep ${PROCESS}`
if [ "${RESULT:-null}" = null ]; then
echo "${PROCESS} not running, starting "$PROCANDARGS
$PROCANDARGS &
else
echo "running"
fi
sleep 10
done
Check if your scripts name doesn't contain $SERVICE. If it does, it will be shown in ps results, causing script to always think that service is running. You can grep it against current filename like this:
#!/bin/sh
SERVICE=$1
if ps ax | grep -v grep | grep -v $0 | grep $SERVICE > /dev/null
then
echo "$SERVICE service running, everything is fine"
else
echo "$SERVICE is not running"
fi
Working one.
!/bin/bash
CHECK=$0
SERVICE=$1
DATE=`date`
OUTPUT=$(ps aux | grep -v grep | grep -v $CHECK |grep $1)
echo $OUTPUT
if [ "${#OUTPUT}" -gt 0 ] ;
then echo "$DATE: $SERVICE service running, everything is fine"
else echo "$DATE: $SERVICE is not running"
fi
Despite some success with the /dev/null approach in bash. When I pushed the solution to cron it failed. Checking the size of a returned command worked perfectly though. The ampersrand allows bash to exit.
#!/bin/bash
SERVICE=/path/to/my/service
result=$(ps ax|grep -v grep|grep $SERVICE)
echo ${#result}
if ${#result}> 0
then
echo " Working!"
else
echo "Not Working.....Restarting"
/usr/bin/xvfb-run -a /opt/python27/bin/python2.7 SERVICE &
fi
#!/bin/bash
ps axho comm| grep $1 > /dev/null
result=$?
echo "exit code: ${result}"
if [ "${result}" -eq "0" ] ; then
echo "`date`: $SERVICE service running, everything is fine"
else
echo "`date`: $SERVICE is not running"
/etc/init.d/$1 restart
fi
Something like this
Those are helpful hints. I just needed to know if a service was running when I started the script, so I could leave the service in the same state when I left. I ended up using this:
HTTPDSERVICE=$(ps -A | grep httpd | head -1)
[ -z "$HTTPDSERVICE" ] && echo "No apache service running."
I found the problem. ps -ae instead ps -a works.
I guess it has to do with my rights in the shared hosting environment. There's apparently a difference between executing "ps -a" from the command line and executing it from within a bash-script.
A simple script version of one of Andor's above suggestions:
!/bin/bash
pgrep $1 && echo Running
If the above script is called test.sh then, in order to test, type:
test.sh NameOfProcessToCheck
e.g.
test.sh php
I was wondering if it would be a good idea to have progressive attempts at a process, so you pass this func a process name func_terminate_process "firefox" and it tires things more nicely first, then moves on to kill.
# -- NICE: try to use killall to stop process(s)
killall ${1} > /dev/null 2>&1 ;sleep 10
# -- if we do not see the process, just end the function
pgrep ${1} > /dev/null 2>&1 || return
# -- UGLY: Step trough every pid and use kill -9 on them individually
for PID in $(pidof ${1}) ;do
echo "Terminating Process: [${1}], PID [${PID}]"
kill -9 ${PID} ;sleep 10
# -- NASTY: If kill -9 fails, try SIGTERM on PID
if ps -p ${PID} > /dev/null ;then
echo "${PID} is still running, forcefully terminating with SIGTERM"
kill -SIGTERM ${PID} ;sleep 10
fi
done
# -- If after all that, we still see the process, report that to the screen.
pgrep ${1} > /dev/null 2>&1 && echo "Error, unable to terminate all or any of [${1}]" || echo "Terminate process [${1}] : SUCCESSFUL"
I need to do this from time to time and end up hacking the command line until it works.
For example, here I want to see if I have any SSH connections, (the 8th column returned by "ps" is the running "path-to-procname" and is filtered by "awk":
ps | awk -e '{ print $8 }' | grep ssh | sed -e 's/.*\///g'
Then I put it in a shell-script, ("eval"-ing the command line inside of backticks), like this:
#!/bin/bash
VNC_STRING=`ps | awk -e '{ print $8 }' | grep vnc | sed -e 's/.*\///g'`
if [ ! -z "$VNC_STRING" ]; then
echo "The VNC STRING is not empty, therefore your process is running."
fi
The "sed" part trims the path to the exact token and might not be necessary for your needs.
Here's my example I used to get your answer. I wrote it to automatically create 2 SSH tunnels and launch a VNC client for each.
I run it from my Cygwin shell to do admin to my backend from my windows workstation, so I can jump to UNIX/LINUX-land with one command, (this also assumes the client rsa keys have already been "ssh-copy-id"-ed and are known to the remote host).
It's idempotent in that each proc/command only fires when their $VAR eval's to an empty string.
It appends " | wc -l" to store the number of running procs that match, (i.e., number of lines found), instead of proc-name for each $VAR to suit my needs. I keep the "echo" statements so I can re-run and diagnose the state of both connections.
#!/bin/bash
SSH_COUNT=`eval ps | awk -e '{ print $8 }' | grep ssh | sed -e 's/.*\///g' | wc -l`
VNC_COUNT=`eval ps | awk -e '{ print $8 }' | grep vnc | sed -e 's/.*\///g' | wc -l`
if [ $SSH_COUNT = "2" ]; then
echo "There are already 2 SSH tunnels."
elif [ $SSH_COUNT = "1" ]; then
echo "There is only 1 SSH tunnel."
elif [ $SSH_COUNT = "0" ]; then
echo "connecting 2 SSH tunnels."
ssh -L 5901:localhost:5901 -f -l USER1 HOST1 sleep 10;
ssh -L 5904:localhost:5904 -f -l USER2 HOST2 sleep 10;
fi
if [ $VNC_COUNT = "2" ]; then
echo "There are already 2 VNC sessions."
elif [ $VNC_COUNT = "1" ]; then
echo "There is only 1 VNC session."
elif [ $VNC_COUNT = "0" ]; then
echo "launching 2 vnc sessions."
vncviewer.exe localhost:1 &
vncviewer.exe localhost:4 &
fi
This is very perl-like to me and possibly more unix utils than true shell scripting. I know there are lots of "MAGIC" numbers and cheezy hard-coded values but it works, (I think I'm also in poor taste for using so much UPPERCASE too). Flexibility can be added with some cmd-line args to make this more versatile but I wanted to share what worked for me. Please improve and share. Cheers.
A solution with service and awk that takes in a comma-delimited list of service names.
First it's probably a good bet you'll need root privileges to do what you want. If you don't need to check then you can remove that part.
#!/usr/bin/env bash
# First parameter is a comma-delimited string of service names i.e. service1,service2,service3
SERVICES=$1
ALL_SERVICES_STARTED=true
if [ $EUID -ne 0 ]; then
if [ "$(id -u)" != "0" ]; then
echo "root privileges are required" 1>&2
exit 1
fi
exit 1
fi
for service in ${SERVICES//,/ }
do
STATUS=$(service ${service} status | awk '{print $2}')
if [ "${STATUS}" != "started" ]; then
echo "${service} not started"
ALL_SERVICES_STARTED=false
fi
done
if ${ALL_SERVICES_STARTED} ; then
echo "All services started"
exit 0
else
echo "Check Failed"
exit 1
fi
The most simple check by process name :
bash -c 'checkproc ssh.exe ; while [ $? -eq 0 ] ; do echo "proc running";sleep 10; checkproc ssh.exe; done'