Aborting a shell script if any command returns a non-zero value

Question

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

User · Answer

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

User · Answer

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   gt  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

User · Answer

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

User · Answer

An expression like  dosomething1  amp  amp  dosomething2  amp  amp  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  amp  amp  echo  done  echo    1

User · Answer

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   gt  amp 2 else   ret      echo  command failed with exit code  ret   gt  amp 2   exit  ret fi

User · Answer

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  amp  amp  or    list   See the bash 1  man page on the  set  internal command for more details   I personally start almost all shell scripts with  set -e    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

User · Answer

Run it with -e or set -e at the top   Also look at set -u

User · Answer

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

User · Answer

bin bash -e   should suffice

[linux] Aborting a shell script if any command returns a non-zero value

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