Underscore

The special shell variable $_ holds the last argument of the previous command. It’s especially handy in interactive Bash sessions and scripts when you want to avoid retyping long or dynamic arguments.

Why Use `$_`?

Boosts productivity by reducing repetitive typing
Seamlessly reuses file names, directory paths, or any last argument
Works in interactive shells and within scripts

$_ refers strictly to the last argument of the previous command. If that command had no arguments, $_ will be empty.

Interactive Shell Examples

Listing and Copying a File

$ ls -l file.conf
total 16
-rw-r--r-- 1 root root 896 Jun 18 2020 file.conf
$ cp $_ /tmp

Here, $_ expands to file.conf, so you don’t have to type it twice.

Chaining Commands

$ ls -l file.conf; echo "Done"
total 16
-rw-r--r-- 1 root root 896 Jan 18 2020 file.conf
Done
$ echo $_
Done

Since the last command was echo "Done", $_ now contains Done.

Using `$_` in Scripts

#!/usr/bin/env bash

# Create a new directory
mkdir project_build

# Change into the new directory using $_
cd $_

# Show current path
pwd

Here, $_ saves you from typing project_build again.

Common Use Cases

Scenario	Last Command	`$_` Value
Copying a file	`cp large_archive.tar.gz /backup`	`/backup`
Editing a file	`vim /etc/nginx/nginx.conf`	`/etc/nginx/nginx.conf`
Moving a directory	`mv logs_old logs_archive`	`logs_archive`
Pipelining commands	`grep ERROR logfile.log`	`logfile.log`

Advanced Examples

# Remove a file, then verify its removal
rm temp_data.csv
echo "Removed" $_

# Using in a pipeline
find . -name '*.log' | xargs gzip
echo "Compressed" $_

Watch Video

Zero

Dash

Introduction

Conventions

Refresher

Streams

Expansions - Part One

Globs

Expansions - Part Two

Special Shell Variables

Arrays

Good Practices applied

awk

sed

Why Use `$_`?

Interactive Shell Examples

Listing and Copying a File

Chaining Commands

Using `$_` in Scripts

Common Use Cases

Advanced Examples

Further Reading

Watch Video

​Why Use $_?

​Interactive Shell Examples

​Listing and Copying a File

​Chaining Commands

​Using $_ in Scripts

​Common Use Cases

​Advanced Examples

​Further Reading

Watch Video

Why Use `$_`?

Interactive Shell Examples

Listing and Copying a File

Chaining Commands

Using `$_` in Scripts

Common Use Cases

Advanced Examples

Further Reading