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 · Accepted 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

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

bin bash -e   should suffice

User · Answer

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

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      amp  amp  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      amp  amp  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

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

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

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