What is Linux true Command?
In this tutorial we learn how to use true command in Linux. true command in Linux will do nothing, successfully. This command is the opposite of false command.
true [ignored command line arguments] true OPTION
Using true command in Linux
To use true we can invoke the command without any options or parameters.
true command will gives us no output or anything at all. But we can check the exit status of the true command using the command below right after invoking true command.
echo $? 0
The exit status 0 above shows that the command executed successfully.
Using true Command To Force Exit Status 0 in Linux Script
You might be wondering what is the use case of Linux true command? You will usually this command being found in a shell script to make sure the command that we have provides exit status 0.
The next question will be, why we want to make sure we get exit status 0? In a shell script if we don’t get exit status 0 the script will be terminated and exit. For non critical command we can make sure that the command will still continue to run even though the command is not successfully run.
The format of the command will be similar to
COMMAND || true
The double pipe
|| above means OR. If the first command (command on the left) successfully run, the second command will not be invoked, but if the first command failed. The second command will be invoked.
Since the second command is true, then the exit status will always be 0. For this tutorial, let’s create a new directory named private directory.
If we tried to remove the directory it will be failed since it is a directory.
$ rm -f privatedir/ rm: cannot remove 'privatedir/': Is a directory
If we check the exit status of the command above. The exit status will be 1
echo $? 1
Now if we run the command to remove privatedir directory above but with true command. The exit status will be 0.
rm -f privatedir/ || true rm: cannot remove 'privatedir/': Is a directory
It will still show error message that the removal failed but if we check the exit status, the exit status will be 0
echo $? 0
The sample above is the most common usage of true command in Linux.
true Command Manual / Help
We can use
info command to see the manual page of true command.
true command also have code
man page of the true command can be opened using the command below. To exit man or info page you can press
Info page for the true command can be opened using command below.
To open help page from true command we can run command below.
Linux true Command Source Code
You can find true command source code from the folowing repositories:
- [GitHub] GNU Coreutils true command source code
- true source code on GNU Savannah cgit
- [GNU Savannah gitweb] true source code on
Related Linux Commands
You can read tutorials of related Linux commands below:
In this tutorial we learn how to use true in Linux with practical examples. Visit our Linux Commands guide to learn more about using command line interface in Linux.