# Shell Functions

> Source: https://learn-bash.net/shell-functions/
> Part of Learn Bash, free to read.

Like other programming languages, the shell may have functions. A function is a subroutine that implements a set of commands and operations. It is useful for repeated tasks.

```bash
# basic construct
function_name {
  command...
}
```

Functions are called simply by writing their names. A function call is equivalent to a command. Parameters may be passed to a function, by specifying them after the function name. The first parameter is referred to in the function as $1, the second as $2 etc.

```bash
function function_B {
  echo "Function B."
}
function function_A {
  echo "$1"
}
function adder {
  echo "$(($1 + $2))"
}

# FUNCTION CALLS
# Pass parameter to function A
function_A "Function A."     # Function A.
function_B                   # Function B.
# Pass two parameters to function adder
adder 12 56                  # 68
```