Conditions (GNU Coreutils 9.0)
From Get docs
This section describes commands that are primarily useful for their exit status, rather than their output. Thus, they are often used as the condition of shell
if statements, or as the last command in a pipeline.
|• false invocation||Do nothing, unsuccessfully.|
|• true invocation||Do nothing, successfully.|
|• test invocation||Check file types and compare values.|
|• expr invocation||Evaluate expressions.|