If i copy and paste all the commands into the terminal..
some do not even go through.
so the solution is perhaps to turn the file into an executable file
and then execute it.
but what if some commands fail.
the script keeps on executing the other commands.
obviously there is no solution to this right ?
The easiest way to do this is to use the -e option in your shell. For example:
#!/bin/sh -e
command1
command2
In this script, if command1 fails, then the script as a whole will fail at that point without running any further commands.
You can check the error code from commands you run
#!/bin/bash
function test {
"$#"
status=$?
if [ $status -ne 0 ]; then
echo "error with $1"
exit 255
fi
return $status
}
test ls
test ps -ef
test not_a_command
taken from here for more information Checking Bash exit status of several commands efficiently
#Terminal, you were almost there.
If you just stick && on the end of each command, then execution will stop with the first failure (ie. the first command that returns a non-zero exit code).
Example:
#!/bin/sh
true &&
echo 'got here' &&
echo 'got here too' &&
false &&
echo 'also got here'
produces the output
got here
got here too
(Actually, I thought it would also require line-continuation markers too: && \, but a quick test showed otherwise.)
Note: All of the above assumes that your shell is bash; I can't speak for other shells.
Related
I have a folder of executable scripts, and some of them have Python shebangs, while others have Bash shebangs, etc. We have a cron job that runs this folder of scripts nightly, and the hope is that any error in any script will exit the job.
The scripts are run with something like: for FILE in $FILES; do ./$FILE; done
The scripts are provided by various people, and while the Python scripts always exit after an error, sometimes developers forget to add set -e in their Bash scripts.
I could have the for-loop use bash -e, but then I need to detect whether the current script is Bash/Python/etc.
I could set -e from the parent script, and then source scripts, but I still need to know which language each script is in, and I'd prefer them to run as subshells so script contributors don't have to worry about messing up the parent.
greping the shebangs is a short tweak, but knowing the flexibility of Bash, I'd be surprised if there weren't a way to "export" an option that affected all child scripts, in the same way you can export a variable. And, there have been many cases in general where I've forgotten "set -e", so it could be nice to know more options for fool-proofing things.
I see some options for inheriting -e for subshells involved in command substitution, but not in general.
Disclaimer: Never, ever do this! It's a huge disservice to everyone involved. You will introduce failures both in scripts with meticulous error handling, and in scripts without it.
Anyways, no one likes being told "don't do that" on StackOverflow, so my suggestion would be to identify scripts and invoke them with their shebang string plus -e:
for f in ./*
do
# Determine if the script is a shell script
if [[ $(file -i "$f") == *text/x-shellscript* ]]
then
# Read the first line
read -r shebang < "$f"
# The script shouldn't have been identified as a shell script without
# a shebang, but check anyways
if [[ $shebang != "#!"* ]]
then
echo "No idea what $f is" >&2
continue
fi
# Strip off the #! and run it with -e and the file
shebang=${shebang#??}
$shebang -e "$f"
else
# It's some other kind of executable, just run it directly
"$f"
fi
done
Here's a script with correct error handling that now stops working:
#!/bin/bash
my-service start
ret=$?
if [ $ret -eq 127 ]
then
# Use legacy invocation instead
start-my-service
ret=$?
fi
exit "$ret"
Here's a script without error handling that now stops working:
#!/bin/sh
err=$(grep "ERROR" file.log)
if [ -z "$err" ]
then
echo "Run was successful"
exit 0
else
echo "Run failed: $err"
exit 1
fi
I run a Jenkins pipeline job with Groovy. The Groovy calls bash scripts for each step.
I want to fail the whole job when something in the way has errors.
For Groovy I use the returnStatus: true.
For Bash I use set -e.
But a bash script with set -e, does not exit if, for example, a while statement has errors. This is what should actually happen, according to the Linux manual page for 'set'.
I would like to know how to exit immediately in that scenario.
The script:
[jenkins-user#jenkins ~]$ cat script.sh
#!/bin/bash
set -xe
FILE=commands.txt
echo "echos before while"
# Run the commands in the commands file
while read COMMAND
do
$COMMAND
done < $FILE
echo $?
echo "echos after faulty while"
Let's say 'commands.txt' doesn't exist.
Running script:
[jenkins-user#jenkins ~]$ sh script.sh
echos before while
script.sh: line 13: commands.txt: No such file or directory
1
echos after faulty while
[jenkins-user#jenkins ~]$ echo $?
0
Although the while statement returns exit code 1, the script continues and ends successfully, as checked right after, with echo $?.
This is how I force the Groovy to fail, after a step with bash/python/etc command/script returns a none-zero exit code:
pipeline {
agent any
stages {
stage("A") {
steps {
script {
def rc = sh(script: "sh A.sh", returnStatus: true)
if (rc != 0) {
error "Failed, exiting now..."
}
}
}
}
}
}
First question, how can I make the SHELL script to fail when the while/if/etc statements have errors? I know I can use command || exit 1 but it doesn't seem elegant if I have dozens of statements like this in the script.
Second question, is my Groovy error handling correct? Can anyone suggest an event better way? Or maybe there is a Jenkins plugin/official way to do so?
First question this link may be helpful Aborting a shell script if any command returns a non-zero value
Second question: You can improve your error handling using try and catch for exception handling.
try{
def rc = sh(script: "sh A.sh", returnStatus: true)
if (rc != 0) {
error "Failed, exiting now..."
}
}
catch (Exception er){
errorMessage = er.getMessage();
}
About the Bash script.
Your issue is that the fail redirection does not abort the bash script, despite the use of set -e. I was surprised my-self. But it's my first disappointment about set -e, so now I consider to not trust it and I abuse of stuff like $command || exit 1 ...
Here you can do the following:
set -xe -o pipefail
cat $FILE | while read command; do $command ; done
But the whole loop should be simplified into:
bash $FILE
Why don't you just use the while exit code and return it? (See this modified version of your script, the last lines)
[jenkins-user#jenkins ~]$ cat script.sh
#!/bin/bash
set -xe
FILE=commands.txt
echo "echos before while"
# Run the commands in the commands file
while read COMMAND
do
$COMMAND
done < $FILE
status=$?
echo "echos after faulty while"
exit $status
[jenkins-user#jenkins ~]$ cat script.sh
#!/bin/bash
set -xe
FILE=commands.txt
echo "echos before while"
# Run the commands in the commands file
while read COMMAND
do
$COMMAND
done < $FILE
echo $?
echo "echos after faulty while"
When yor perform a echo $? after this script it will always be 0, because the last command was echo "echos after faulty while" you can ad an exit 1 at the end of your script. In exit 1 the number 1 will be the error code, you can use other. So the script will be
[jenkins-user#jenkins ~]$ cat script.sh
#!/bin/bash
set -xe
FILE=commands.txt
echo "echos before while"
# Run the commands in the commands file
while read COMMAND
do
$COMMAND
done < $FILE
echo $?
exit 1
Is there a way to execute bash script when I click a program like NetBeans or DropBox on Ubuntu
and execute a bash script when exit it
My idea create bash script on cronjob #reboot check every second if the program exist in the current processes
#!/bin/bash
NameOfprogram="NetBeans"
while [[ true ]]; do
countOfprocess=$(ps -ef |grep $NameOfprogram | wc -l)
if [[ $countOfprocess -gt 1 ]]; then
#execute bash
fi
sleep 1
done
But I think this idea not the best ,Is there a better way to achieve it?
A better approach is to wrap the executable in a script. That means you put a script with the name of the program in your path (probably $HOME/bin) and Linux will use that instead of the real executable.
Now you can execute the real program using:
/usr/bin/NetBeans "$#"
So to execute the real executable, you just put the absolute path in front of the name. The odd "$#" too pass on any arguments someone might have given the script.
Put a loop around this:
while [[ true ]]; do
/usr/bin/NetBeans "$#"
done
But there is a problem: You can't exit this program anymore. As soon as you try, it restarts. So if you just want a restart when it crashes:
while [[ true ]]; do
/usr/bin/NetBeans "$#" && exit 0
done
As long as the program exits because of an error, it will be restarted. If you quit it, the script will stop.
Since cruise control is full of bugs that have wasted my entire week, I have decided the existing shell scripts I have are simpler and thus better.
Here is what I have so far
svn update /var/www/k12/
#svn log --revision "HEAD" /var/www/code/ | head -2 | tail -1 | awk '{print $1}' > /var/www/path/version.txt
# upload the files
rsync -ar --verbose --stats --progress --delete --exclude=*.svn /var/www/code/ example.com:/home/path
# bring database up to date
ssh example.com 'php /path/tasks/dbrefactor.php'
# notify me
ssh example.com 'php /path/tasks/build.php'
Only thing is the other day I changed the paths and forgot to update the rsync call. As a result the "notify me" step ran several times while I was figuring stuff out.
I know in linux you can do command1 && command2 and if command 1 "fails" command2 will not run, but how can I observe the "failure/success" exit codes for debugging purposes. Some of the scripts I wrote myself and I'm sure I will need to do something special.
The best option, especially for unattended scripts, is to set the -e shell option:
#!/bin/sh -e
or
set -e
This will cause the shell to stop executing if any (untested) command exits with a nonzero error code.
-e Exit immediately if a simple command (see SHELL GRAMMAR
above) exits with a non-zero status. The shell does not
exit if the command that fails is part of an until or
while loop, part of an if statement, part of a && or ||
list, or if the command's return value is being inverted
via !. A trap on ERR, if set, is executed before the
shell exits.
The exit code of a previous process happens to be in $? variable right after its execution. Usually (that's not required, but it's the convention everyone follows) the exit code of a successful command will be equal to 0, and any other value means an error.
Remember of the caveats! One of them is that after these commands:
svn log --revision "HEAD" /var/www/code/ | head -2 | tail -1 | awk '{print $1}'
echo "$?"
the zero result would most likely be returned, because in the $? the return code of awk is contained. To avoid it, set the pipefail option somewhere above the code:
set -o pipefail 1
The return value of the last-run command is stored in the variable $?. You can use that to determine which command to run next. Overview of special variables.
i think $? contains the last exit code
if [[ -z $? ]]
then
# notify me
ssh example.com 'php /path/tasks/build.php'
fi
I would suggest you can use the exit non zero at the points where the failure is expected and before processing step further you will check
if [ $? -neq 0 ]
then there is a failure.
The $? will always return a non zero number if the last process does not executed successfully.
I have a Bash shell script that invokes a number of commands.
I would like to have the shell script automatically exit with a return value of 1 if any of the commands return a non-zero value.
Is this possible without explicitly checking the result of each command?
For example,
dosomething1
if [[ $? -ne 0 ]]; then
exit 1
fi
dosomething2
if [[ $? -ne 0 ]]; then
exit 1
fi
Add this to the beginning of the script:
set -e
This will cause the shell to exit immediately if a simple command exits with a nonzero exit value. A simple command is any command not part of an if, while, or until test, or part of an && or || list.
See the bash manual on the "set" internal command for more details.
It's really annoying to have a script stubbornly continue when something fails in the middle and breaks assumptions for the rest of the script. I personally start almost all portable shell scripts with set -e.
If I'm working with bash specifically, I'll start with
set -Eeuo pipefail
This covers more error handling in a similar fashion. I consider these as sane defaults for new bash programs. Refer to the bash manual for more information on what these options do.
To add to the accepted answer:
Bear in mind that set -e sometimes is not enough, specially if you have pipes.
For example, suppose you have this script
#!/bin/bash
set -e
./configure > configure.log
make
... which works as expected: an error in configure aborts the execution.
Tomorrow you make a seemingly trivial change:
#!/bin/bash
set -e
./configure | tee configure.log
make
... and now it does not work. This is explained here, and a workaround (Bash only) is provided:
#!/bin/bash
set -e
set -o pipefail
./configure | tee configure.log
make
The if statements in your example are unnecessary. Just do it like this:
dosomething1 || exit 1
If you take Ville Laurikari's advice and use set -e then for some commands you may need to use this:
dosomething || true
The || true will make the command pipeline have a true return value even if the command fails so the the -e option will not kill the script.
If you have cleanup you need to do on exit, you can also use 'trap' with the pseudo-signal ERR. This works the same way as trapping INT or any other signal; bash throws ERR if any command exits with a nonzero value:
# Create the trap with
# trap COMMAND SIGNAME [SIGNAME2 SIGNAME3...]
trap "rm -f /tmp/$MYTMPFILE; exit 1" ERR INT TERM
command1
command2
command3
# Partially turn off the trap.
trap - ERR
# Now a control-C will still cause cleanup, but
# a nonzero exit code won't:
ps aux | grep blahblahblah
Or, especially if you're using "set -e", you could trap EXIT; your trap will then be executed when the script exits for any reason, including a normal end, interrupts, an exit caused by the -e option, etc.
The $? variable is rarely needed. The pseudo-idiom command; if [ $? -eq 0 ]; then X; fi should always be written as if command; then X; fi.
The cases where $? is required is when it needs to be checked against multiple values:
command
case $? in
(0) X;;
(1) Y;;
(2) Z;;
esac
or when $? needs to be reused or otherwise manipulated:
if command; then
echo "command successful" >&2
else
ret=$?
echo "command failed with exit code $ret" >&2
exit $ret
fi
Run it with -e or set -e at the top.
Also look at set -u.
On error, the below script will print a RED error message and exit.
Put this at the top of your bash script:
# BASH error handling:
# exit on command failure
set -e
# keep track of the last executed command
trap 'LAST_COMMAND=$CURRENT_COMMAND; CURRENT_COMMAND=$BASH_COMMAND' DEBUG
# on error: print the failed command
trap 'ERROR_CODE=$?; FAILED_COMMAND=$LAST_COMMAND; tput setaf 1; echo "ERROR: command \"$FAILED_COMMAND\" failed with exit code $ERROR_CODE"; put sgr0;' ERR INT TERM
An expression like
dosomething1 && dosomething2 && dosomething3
will stop processing when one of the commands returns with a non-zero value. For example, the following command will never print "done":
cat nosuchfile && echo "done"
echo $?
1
#!/bin/bash -e
should suffice.
I am just throwing in another one for reference since there was an additional question to Mark Edgars input and here is an additional example and touches on the topic overall:
[[ `cmd` ]] && echo success_else_silence
Which is the same as cmd || exit errcode as someone showed.
For example, I want to make sure a partition is unmounted if mounted:
[[ `mount | grep /dev/sda1` ]] && umount /dev/sda1