Code Reuse In Shell

In shell scripting, unlike some programming languages, there is no built-in module system that allows the use of import syntax as seen in JavaScript or Python. However, you can achieve code reuse through techniques like sourcing external scripts using source or .(dot) commands。

source xx.sh
#or
. xx.sh

Consider the following example where we reuse a varialbe from one script in another:

test3.sh

#!/bin/bash

name=2

echo "test3.sh: name=$name"

test.sh

#!/bin/bash

. ./test3.sh

# 2
echo $name

As demonstrated above, you can share variables between scripts using the source. This allows you to reuse not only variables but also functions and environment variables.

Let’s extend the example to include a function:

test3.sh

#!/bin/bash

name=2

function say {
  name=$1
  echo "say: name=$name"
}

test.sh

#!/bin/bash

. ./test3.sh

# Outputs: say: name=roc
say "roc"

In the above script, the say functions is defined in test3.sh and is then reused in test.sh, demonstrating the flexibility and simplicity of code reuse in shell scripting.

While shell scripting may lack some of the advanced modularity features found in other languages, leveraging sourcing and a consistent variable scope allows for effective code reuse, making you scripts more maintainable and modular.