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meld: Visual File/Directory Comparison and Merging Tool

meld is a graphical user interface (GUI) tool used to visually compare and merge two or three files or directories. It is very useful for code reviews, checking changes before and after applying patches, and resolving version control conflicts.

Overview

Unlike terminal-based text comparison tools such as diff and sdiff, meld compares files in a graphical environment. It clearly highlights differences with various colors and provides interactive features that allow users to merge changes with a simple mouse click. When comparing directories, it also allows you to quickly identify which files have been added, deleted, or modified, enabling intuitive handling of complex code merging tasks.

Key Features

Key features of meld include:

  • Can compare two or three files simultaneously.
  • Visually highlights line-by-line differences with colors for easy identification.
  • Allows merging changes from one file to another with just a mouse click.
  • Recursively compares entire directories, showing the status of files (identical, different, unique).
  • Useful for resolving conflicts by integrating with various version control systems like Git, Mercurial, and Subversion.

Differences from Terminal Commands

meld focuses on visual interaction, unlike terminal commands such as diff.

  • meld: GUI-based, enabling visual difference checking and interactive merging. Primarily used for manual merging tasks.
  • diff / sdiff: Terminal-based, outputs differences in text files. Primarily used for script automation or quick change verification.

Key Options

While meld primarily operates as a GUI, there are several useful options when running it from the terminal.

1) Execution Options

Generated command:

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Description:

`meld` Executes the command.

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Usage Examples

Learn meld's functionality through examples of running it from the terminal.

Compare Two Files

meld file1.txt file2.txt

Compares file1.txt and file2.txt visually in the GUI.

Compare Two Directories

meld dir1 dir2

Recursively compares the contents of dir1 and dir2 directories.

Compare Three Files

meld file1.txt file2.txt file3.txt

Compares file1.txt, file2.txt, and file3.txt side-by-side in three panes. Useful for conflict resolution.

Using meld for Git Conflict Resolution

git mergetool

When a conflict occurs during a Git merge, you can use meld as the default tool for `git mergetool` to resolve the conflict.

Installation

meld is included in the repositories of most Linux distributions. You can easily install it using the commands below.

Debian/Ubuntu

sudo apt update
sudo apt install meld

RHEL/CentOS/Fedora

sudo dnf install meld

Arch Linux

sudo pacman -S meld

Tips & Considerations

Useful information to know when using meld.

Tips

  • meld is a visual tool and therefore only works in a graphical environment like X Window System. X11 forwarding (`ssh -X`) is required to use it on a remote server.
  • The left and right panes in meld represent file 1 and file 2, respectively. You can easily merge changes by clicking the arrow buttons in the middle.
  • You can set meld as the default merge tool for version control systems like Git using the command `git config --global merge.tool meld`.

Related commands

These are commands that are functionally similar or are commonly used together.

diff

diff: Guide to Comparing Files/Directories

git

Git Command Guide: The Core of Version Control Systems

patch

patch: Apply Changes (Patches) to Files

sdiff

sdiff: Compare Two Files Side-by-Side

Same category commands

awk

Mastering the AWK Command: The Magician of Text Processing

cat

cat Command Guide: View and Concatenate File Contents

cmp

cmp: Compare two files byte by byte

column

column: Format text into columns

comm

comm: Compare common and unique lines of two sorted files