Shell Script Interfaces

Usage Line

Explain the Interface

A usage line tells callers which command form the script accepts. It should match the names and options the script actually parses.

Program

Play the script to choose a command name and see the generated usage text.

script_name
usage_line.sh
Replay: real traced execution (multi-file project)
#!/usr/bin/env bash

script_name="deploy.sh"
usage="usage: $script_name [--dry-run] <target>"
echo "$usage"

#!/usr/bin/env bash

script_name="backup.sh"
usage="usage: $script_name [--dry-run] <target>"
echo "$usage"

  1. script_name ← deploy.sh

    3script_name="deploy.sh"4usage="usage: $script_name [--dry-run] <target>"
    values this stepdeploy.shscript_name

  2. usage ← usage: deploy.sh [--dry-run] <target>

    3script_name="deploy.sh"4usage="usage: $script_name [--dry-run] <target>"5echo "$usage"
    values this stepusage: deploy.sh [--dry-run] <target>usagedeploy.shscript_name

  3. echo "$usage"

    4usage="usage: $script_name [--dry-run] <target>"5echo "$usage"
    outputusage: deploy.sh [--dry-run] <target>
    values this stepusage: deploy.sh [--dry-run] <target>usage

  1. script_name ← backup.sh

    3script_name="backup.sh"4usage="usage: $script_name [--dry-run] <target>"
    values this stepbackup.shscript_name

  2. usage ← usage: backup.sh [--dry-run] <target>

    3script_name="backup.sh"4usage="usage: $script_name [--dry-run] <target>"5echo "$usage"
    values this stepusage: backup.sh [--dry-run] <target>usagebackup.shscript_name

  3. echo "$usage"

    4usage="usage: $script_name [--dry-run] <target>"5echo "$usage"
    outputusage: backup.sh [--dry-run] <target>
    values this stepusage: backup.sh [--dry-run] <target>usage
usage Usage text is the short contract shown when a caller needs help.
script name Using the script name variable keeps help text reusable.
argument contract `<target>` signals a required positional argument.