true: The Always Successful Command

Overview

true is a fundamental utility used in Unix and Unix-like operating systems. This command always returns a successful exit status (0), which can be utilized in shell scripting for purposes such as satisfying logical conditions or creating infinite loops.

Primary Uses

Provides an always-true condition in shell scripts
Creates infinite loops (e.g., while true)
Serves as a successful starting point in command chains (e.g., true && command)
For testing and debugging purposes

Key Options

The true command does not have functional options and does not process any arguments. As a standard utility, it only supports the `--help` and `--version` options.

Information

Generated command:

Try combining the commands.

Description:

`true` Executes the command.

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Usage Examples

Examples demonstrating how the true command can be utilized in shell scripts and the terminal.

Basic Usage

true
echo $?

The true command always returns an exit code of 0. You can check the exit code with echo $?.

Usage in a while loop

while true; do
  echo "This message will be printed continuously."
  sleep 1
done

Useful for creating infinite loops. You need to terminate it with Ctrl+C.

Usage in conditional statements

if true; then
  echo "This message will always be printed."
fi

Used to create a condition that is always true.

Usage with logical operators

true && echo "Since true always succeeds, this message will be printed."

Used to ensure the execution of another command, or to indicate that a certain condition is always met.

Tips & Notes

The true command is simple yet can be very useful when writing scripts.

Comparison with the false command

true always returns success (exit code 0), while false always returns failure (exit code 1). These two commands are used complementarily for controlling the logical flow of shell scripts.

true: Exit code 0 (Success)
false: Exit code 1 (Failure)

Performance

The true command is very lightweight and executes quickly. It consumes minimal system resources, so its impact on performance is negligible even when called frequently within scripts.

Built-in vs. External Command

In most shells (like bash, zsh, etc.), true is provided as a shell built-in command, allowing for faster execution. However, it also exists as an external executable file, such as /bin/true.