chapter15.txt

# OBSOLETE SYNTAX

## Shebang

Use `#!/usr/bin/env bash` instead of `#!/bin/bash`.

- The former searches the user's `PATH` to find the `bash` binary.
- The latter assumes it is always installed to `/bin/` which can cause issues.

```shell
# Right:

    #!/usr/bin/env bash

# Wrong:

    #!/bin/bash
```

## Command Substitution

Use `$()` instead of `` ` ` ``.

```shell
# Right.
var="$(command)"

# Wrong.
var=`command`

# $() can easily be nested whereas `` cannot.
var="$(command "$(command)")"
```

## Function Declaration

Do not use the `function` keyword, it reduces compatibility with older versions of `bash`.

```shell
# Right.
do_something() {
    # ...
}

# Wrong.
function do_something() {
    # ...
}
```

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