Title: Fixing a Slow Bash Prompt

Date: 2021-02-01 16:49

Modified: 2021-02-01 16:49

Category: Posts

tags: bash,git,osx,homebrew

cover: static/imgs/default_page_imagev2.jpg

summary: My bash prompt seemed to be slow. Here's how I fixed it

I recently got a new machine for my new job, and so I'm going through all the

"new machine setup" gotchas. Since getting it, I've been finding the

shell/terminal has felt really sluggish. Like I’d hit enter in a terminal and

it’d be 1-2 seconds before the prompt came back allowing me to type anything

again, which makes someone who likes to type a lot of commands in quick

succession get angry. 😠

After a bunch of troubleshooting & reverse engineering I found it came down to

the `__git_ps1` function that displays your current branch in your bash prompt.

How slow was it? Really slow:

``` shell

λ time __git_ps1

(mainline)

real 0m1.746s

user 0m0.044s

sys 0m0.079s

That’s 1.7 seconds every time I hit enter in a terminal because it gets

evaluated as part of producing my bash prompt.

I thought this was weird, so I did a `git --version` and noticed that I was

running `git version 2.24.3 (Apple Git-128)`. That is the special “Apple has

built this version for you and installed as part of Xcode command-line tools”

version.

So, I installed git from Homebrew (`brew install git`), which gave be the same

normal version that anyone on any platform would get (just compiled for OSX),

and also gave me a much newer version (2.30.0). Much faster. How much faster?

Check it out:

λ time __git_ps1

(mainline)

real 0m0.060s

user 0m0.016s

sys 0m0.026s

From 1.7 seconds to 0.06 seconds. Crazy. Now my command prompt is nice and

snappy.