In computer programming, a usage message or help message refers to a brief message displayed by a program that utilizes a command-line interface for execution. This message usually consists of the correct command line usage for the program and includes a list of the correct command-line arguments or options acceptable to said program.
Contents
Usage messages are utilized as a quick way for a program to inform the user of proper command syntax, and should not be substituted for detailed documentation, such as a man page.
Pattern
On Unix-like platforms, usage messages usually follow the same common pattern:
Examples
Here is an example based on the NetBSD source code style guide:
This would indicate that "program" should be called with:
Implementation
For example, if a shell script called "myscript" required at least two parameter to be run, a programmer could create a usage message using something similar to the following:
Explanation of the code:
- $# is number of parameter passed on the command line to the script
- `basename $0` is the output of basename, to strip any path away from the script's filename
- 1>&2 is used to redirect the output of echo to stderr