Creating custom hook scripts in Git - Visual Walkthrough

Process Flow - Creating custom hook scripts

Start: Git event occurs

↓

Check for hook script in .git/hooks/

Yes↓

Execute hook script

↓

Hook script runs commands

↓

Hook script exits with status

↓

Git continues or aborts based on exit status

No↓

Git continues normal operation

When a Git event happens, Git looks for a hook script in the .git/hooks folder. If found, it runs the script and uses its exit status to decide whether to continue or stop.

Execution Sample

Git

#!/bin/sh
# pre-commit hook example

echo "Running pre-commit checks..."
exit 0

This simple pre-commit hook prints a message and allows the commit to proceed.

Process Table

Step	Git Event	Hook Script Found?	Action	Hook Output	Git Behavior
1	User runs git commit	Yes (.git/hooks/pre-commit exists)	Execute pre-commit hook	Running pre-commit checks...	Commit proceeds
2	Hook script exits with 0	N/A	Git continues commit	N/A	Commit successful
3	User runs git commit	No	No hook to run	N/A	Commit proceeds normally
4	User runs git commit	Yes (hook exists)	Execute hook	Error found, exiting 1	Commit aborted

💡 Execution stops after hook script exits; Git uses exit code to continue or abort.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 4
Hook Script Exists	Unknown	Yes	Yes	Yes
Hook Exit Status	N/A	Running	0 (success)	1 (failure)
Git Commit Status	Not started	Running hook	Commit proceeds	Commit aborted

Key Moments - 3 Insights

Why does Git abort the commit when the hook script exits with a non-zero status?

Git treats any non-zero exit code from a hook script as a failure signal, so it stops the commit to prevent unwanted changes. See execution_table row 4.

What happens if there is no hook script for a Git event?

Git simply continues the operation normally without running any script, as shown in execution_table row 3.

Can a hook script print messages during execution?

Yes, hook scripts can print messages to inform the user, like in execution_table row 1 where the message 'Running pre-commit checks...' is printed.

Visual Quiz - 3 Questions

Look at the execution_table, what is the Git behavior when the pre-commit hook exits with 0?

A Commit proceeds successfully

B Commit is aborted

C Git retries the hook

D Git ignores the hook

💡 Hint

Check execution_table row 2 for hook exit status 0 and Git behavior

At which step does Git abort the commit due to hook failure?

A Step 1

B Step 3

C Step 4

D Step 2

💡 Hint

Look at execution_table row 4 where hook exits with 1 and Git aborts

If the hook script is missing, what does Git do?

A Aborts the operation

B Continues normally

C Runs a default script

D Prompts the user

💡 Hint

See execution_table row 3 for no hook script scenario

Concept Snapshot

Git custom hooks are scripts placed in .git/hooks/ that run on Git events.
If the hook script exists, Git runs it and uses its exit code to decide to continue or stop.
Exit code 0 means success; non-zero aborts the Git operation.
Hooks can print messages to guide users.
No hook means Git proceeds normally.

Full Transcript

When you run a Git command like commit, Git checks if a hook script exists in the .git/hooks folder for that event. If it finds one, it runs the script. The script can do checks or tasks and then exits with a status code. If the exit code is zero, Git continues the operation. If it is non-zero, Git stops the operation to prevent problems. If no hook script is found, Git just continues as usual. Hook scripts can print messages to inform you about what they are doing.