How to break out of a loop in Bash?

Question

I want to write a Bash script to process text, which might require a while loop.

For example, a while loop in C:

int done = 0;
while(1) {
  ...
  if(done) break;
}

I want to write a Bash script equivalent to that. But what I usually used and as all the classic examples I read have showed, is this:

while read something;
do
...
done

It offers no help about how to do while(1){} and break;, which is well defined and widely used in C, and I do not have to read data for stdin.

Could anyone help me with a Bash equivalent of the above C code?

vvvvv · Accepted Answer · 2020-11-06 12:42:49Z

361

It's not that different in bash.

workdone=0
while : ; do
  ...
  if [ "$workdone" -ne 0 ]; then
      break
  fi
done

: is the no-op command; its exit status is always 0, so the loop runs until workdone is given a non-zero value.

There are many ways you could set and test the value of workdone in order to exit the loop; the one I show above should work in any POSIX-compatible shell.

edited Nov 6, 2020 at 12:42

vvvvv

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answered Aug 28, 2013 at 13:02

chepner

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1 Comment

micsthepick Over a year ago

also note: depending on how complex the work that is done, you may also use && break or || break depending on the expected return value

lurker · Accepted Answer · 2013-08-28 13:02:35Z

99

while true ; do
    ...
    if [ something ]; then
        break
    fi
done

answered Aug 28, 2013 at 13:02

lurker

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1 Comment

Thend Feb 27 at 7:02

I think this is the most straight forward way to do it, to only difference that I would do is to use double brackets like [[ something if complex ]] thats all.

DevSolar · Accepted Answer · 2025-02-28 13:29:06Z

-3

read -p "Hey dear user, let's play a game, : " answer
int done = 0
while [[ $answer != "yes" ]]; do

    read -p "guess a number from 10 to 100 : " answer

    if [[  $answer == 70 ]]; then

        echo "Congratulations! You guessed the number."

    elif [[  $answern -lt 70 ]]; then

        echo " dear user, u too close"

    elif [[  $answer -gt 70 ]]; then

        echo " u are to far, dear user"

    if (done); break

    fi
 
done

edited Feb 28 at 13:29

DevSolar

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answered Feb 28 at 11:33

Said Bourhabi

1

1 Comment

DevSolar Feb 28 at 13:30

You might want to give this another try, because neither the logic nor the syntax of that last if checks out. (done is never set, if (done) is a weird way to check for it being set, and the if is inside the last elif.) Also, I don't feel it adds anything to the answers already given.

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