Shell Script Interfaces

Argument Default

Name an Input

A script interface starts with the values callers can pass. Defaults keep the command predictable when an argument is omitted.

Program

Play the script to choose a modeled first argument and see the effective project name.

argument_default.sh 
#!/usr/bin/env bash

arg_project=
project="${arg_project:-demo}"
echo "project=$project"

#!/usr/bin/env bash

arg_project=
project="${arg_project:-demo}"
echo "project=$project"
argument A script argument is caller-provided input.
default `${name:-fallback}` supplies a fallback when the input is empty.
interface value Copying the effective value into a named variable makes later code easier to read.