How to use the command 'git cat-file' (with examples)

Git is a distributed version control system that allows multiple people to work on the same project simultaneously. The ‘git cat-file’ command provides information about Git repository objects, such as the content, type, and size. This article will explain how to use the ‘git cat-file’ command in various scenarios.

Use case 1: Get the size of the HEAD commit in bytes

Code:

git cat-file -s HEAD

Motivation: Knowing the size of the HEAD commit can be useful for tracking changes or optimizing repository storage. By using the ‘git cat-file’ command with the ‘-s’ option followed by ‘HEAD’, you can retrieve the size of the latest commit in bytes.

Explanation:

• ‘cat-file’: the command used to provide content or type and size information for Git repository objects.
• ‘-s’: the option used to display the size of the Git object.
• ‘HEAD’: a reference to the latest commit in the current branch.

Example output:

174

Use case 2: Get the type of a given Git object

Code:

git cat-file -t 8c442dc3

Motivation: Identifying the type of a Git object is useful for understanding how it is used in the repository. By using the ‘git cat-file’ command with the ‘-t’ option followed by the object’s hash, you can retrieve its type (blob, tree, commit, tag).

Explanation:

• ‘-t’: the option used to display the type of the Git object.
• ‘8c442dc3’: the hash of the Git object to examine.

Example output:

commit

Use case 3: Pretty-print the contents of a given Git object based on its type

Code:

git cat-file -p HEAD~2

Motivation: Reviewing the contents of a Git object can provide a better understanding of changes made in the repository. By using the ‘git cat-file’ command with the ‘-p’ option followed by a reference to a Git object, you can display its contents in a human-readable format.

Explanation:

• ‘-p’: the option used to pretty-print the contents of the Git object.
• ‘HEAD~2’: a reference to the parent commit of the parent commit of the latest commit.

Example output:

tree 9dd3a77616490edf3d0feb7e0e34641258eab45f
author John Doe <johndoe@example.com> 1625947312 +0300
committer John Doe <johndoe@example.com> 1625947312 +0300

Initial commit

Conclusion:

The ‘git cat-file’ command is a versatile tool that provides information about Git repository objects. It can be used to retrieve the size, type, and contents of various Git objects. By understanding the different use cases of this command, you can effectively analyze and manipulate your Git repository.