What is /bin/true?

Question

On a Linux system, what is /bin/true? What is it used for?

/foo/bar || true (works if /bin/true) is in the path. While not labeled as such, this question does explain something that is useful in shell scripts, makefiles, etc.. thus not voting to close. — Tim Post, Feb 01 '10 at 14:16
You may want to have a look at [the source code of them](https://askubuntu.com/questions/454117/why-is-bin-true-such-a-large-file-how-would-i-find-the-source-code); since I was curious. — Константин Ван, Jun 07 '17 at 05:42

camh · Accepted Answer · 2016-07-30T21:35:19.420

86

/bin/true is a command that returns 0 (a truth value in the shell).

Its purpose is to use in places in a shell script where you would normally use a literal such as "true" in a programming language, but where the shell will only take a command to run.

/bin/false is the opposite that returns non-zero (a false value in the shell).

edited Jul 30 '16 at 21:35

answered Feb 01 '10 at 08:24

camh

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score 28 · Answer 2 · edited Dec 16 '13 at 10:23

28

From the man page:

true - do nothing, successfully

true returns a status 0.

edited Dec 16 '13 at 10:23

devnull

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answered Feb 01 '10 at 08:23

user231967

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SyaZ: You may also be amused by the description of `false(1)`: "do nothing, unsuccessfully". – camh Feb 02 '12 at 10:49

score 9 · Answer 3 · answered Dec 06 '13 at 00:42

Note, it's not just silly or visually nice. It helps for example to exit a program without activating the end handlers which might mess up when doing multi threading or forked programs. Like in perl:

#!/usr/bin/env perl

exec "/bin/true";

END {
  print "This wont get printed .. would have if I just 'exit' or 'die'\n";
}

score 2 · Answer 4 · answered Sep 20 '16 at 22:25

I've seen it used to fool a system operation into thinking a command has run when it hasn't. If a command is faulty eg looping, you can replace it with a symlink to 'true' to get the master job to run. Only a good idea if the job replaced isn't essential.

Marcus Thornton · Answer 5 · 2020-07-12T21:41:16.813

1

Simply saying its a program returning 0. Sometimes we need to get this value to let the script more readable. It is usually used when you need to use a command for a true value.

edited Jul 12 '20 at 21:41

answered Jun 13 '13 at 10:21

Marcus Thornton

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How about adding an example? – codeforester May 19 '20 at 00:00

score 0 · Answer 6 · answered Oct 22 '20 at 01:09

0

In the UNIX shells, it's used for the same purposes as boolean constants true and false in any other language.

while true; do
    something
done

flag=true
...
if $flag; then
    something
done

answered Oct 22 '20 at 01:09

Jordan Brown

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What is /bin/true?

6 Answers6

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