dirname - Linux

Overview

The dirname command in Linux extracts the directory path from a given file path. It strips the non-directory suffix from the file name and returns the directory portion. This command is particularly useful in scripting and programming where you need to manipulate file path information dynamically.

Syntax

The basic syntax of the dirname command is:

dirname [OPTION] NAME...

NAME…: This parameter is the full file path from which you want to extract the directory portion. You can specify multiple paths.

Options/Flags

dirname comes with the following options:

-z, --zero: End each output line with a zero byte (ASCII NUL) instead of a newline. This option is useful when dealing with filenames that contain newlines.
--help: Display a help message and exit.
--version: Output version information and exit.

Examples

Here are some examples of using dirname:

Basic Usage:
Extract the directory path from a full file path:
```
dirname /usr/bin/sort
```
Output:
```
/usr/bin
```
Multiple Paths:
Get directory names for multiple paths:
```
dirname /etc/passwd /usr/bin/sort
```
Output:
```
/etc
/usr/bin
```
Using with Zero Byte Separator:
When handling filenames that might contain newlines:
```
dirname -z /a/b/c/newline_character_file
```
This outputs /a/b/c followed by a NUL character.

Common Issues

Relative Paths:
Users might expect dirname to return a dot (.) for names without slashes. Instead, it returns the path as is:
```
dirname filename
```
Output:
```
.
```
Note: This is actually the expected behavior by POSIX standard.

Integration

dirname can be integrated with other commands to form powerful command chains:

Scripting Example:
A script to copy a file to the same directory as another file:

#!/bin/bash
file1="/path/to/source/file"
file2="/another/path/target"
cp "$file1" "$(dirname "$file2")"

Combining with xargs:
To find the directory names of all .sh files and process them:
```
find . -name "*.sh" -print | xargs dirname | uniq
```

basename: Extracts the filename from a path.
cd: Changes the directory.
pwd: Prints the current directory.

For more information, refer to the dirname(1) and dirname(3) man pages, or the GNU Core Utilities documentation online.