In a Bash script how can I exit the entire script if a certain condition occurs

Question

I m writing a script in Bash to test some code  However  it seems silly to run the tests if compiling the code fails in the first place  in which case I ll just abort the tests   Is there a way I can do this without wrapping the entire script inside of a while loop and using breaks  Something like a dun dun dun goto

User · Answer

I have the same question but cannot ask it because it would be a duplicate.

The accepted answer, using exit, does not work when the script is a bit more complicated. If you use a background process to check for the condition, exit only exits that process, as it runs in a sub-shell. To kill the script, you have to explicitly kill it (at least that is the only way I know).

Here is a little script on how to do it:

#!/bin/bash

boom() {
    while true; do sleep 1.2; echo boom; done
}

f() {
    echo Hello
    N=0
    while
        ((N++ <10))
    do
        sleep 1
        echo $N
        #        ((N > 5)) && exit 4 # does not work
        ((N > 5)) && { kill -9 $$; exit 5; } # works 
    done
}

boom &
f &

while true; do sleep 0.5; echo beep; done

This is a better answer but still incomplete a I really don't know how to get rid of the boom part.

User · Answer

If you will invoke the script with source  you can use return  lt x gt  where  lt x gt  will be the script exit status  use a non-zero value for error or false   But if you invoke an executable script  i e   directly with its filename   the return statement will result in a complain  error message  return  can only  return  from a function or sourced script     If exit  lt x gt  is used instead  when the script is invoked with source  it will result in exiting the shell that started the script  but an executable script will just terminate  as expected   To handle either case in the same script  you can use  return  lt x gt  2 gt   dev null    exit  lt x gt    This will handle whichever invocation may be suitable  That is assuming you will use this statement at the script s top level  I would advise against directly exiting the script from within a function   Note   lt x gt  is supposed to be just a number

User · Answer

A SysOps guy once taught me the Three-Fingered Claw technique   yell     echo   0       gt  amp 2    die     yell       exit 111    try             die  cannot          These functions are  NIX OS and shell flavor-robust  Put them at the beginning of your script  bash or otherwise   try   your statement and code on   Explanation   based on  flying sheep comment     yell  print the script name and all arguments to stderr     0 is the path to the script      are all arguments    gt  amp 2 means  gt  redirect stdout to  amp  pipe 2  pipe 1 would be stdout itself    die does the same as yell  but exits with a non-0 exit status  which means    fail      try uses the     boolean OR   which only evaluates the right side if the left one failed        is all arguments again  but different

User · Answer

Use set -e     bin bash  set -e   bin command-that-fails  bin command-that-fails2   The script will terminate after the first line that fails  returns nonzero exit code    In this case  command-that-fails2 will not run   If you were to check the return status of every single command  your script would look like this      bin bash    I m assuming you re using make  cd  project-dir make if       -ne 0      then     exit 1 fi  cd  project-dir2 make if       -ne 0      then     exit 1 fi   With set -e it would look like      bin bash  set -e  cd  project-dir make  cd  project-dir2 make   Any command that fails will cause the entire script to fail and return an exit status you can check with      If your script is very long or you re building a lot of stuff it s going to get pretty ugly if you add return status checks everywhere

User · Answer

Instead of if construct  you can leverage the short-circuit evaluation      usr bin env bash  echo   1 1  echo   2 0                 division by 0 but execution of script proceeds echo   3 1   echo   4 0      exit      script halted with code 1 returned from  echo  echo   5 1    Note the pair of parentheses which is necessary because of priority of alternation operator     is a special variable set to exit code of most recently called command

User · Answer

I often include a function called run   to handle errors   Every call I want to make is passed to this function so the entire script exits when a failure is hit    The advantage of this over the set -e solution is that the script doesn t exit silently when a line fails  and can tell you what the problem is   In the following example  the 3rd line is not executed because the script exits at the call to false   function run       cmd output   eval  1    return value      if    return value    0    then     echo  Command  1 failed      exit -1   else     echo  output   cmd output      echo  Command succeeded     fi   return  return value   run  date  run  false  run  date

User · Answer

Try this statement   exit 1   Replace 1 with appropriate error codes  See also Exit Codes With Special Meanings

[bash] In a Bash script, how can I exit the entire script if a certain condition occurs?

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