For some time I have been annoyed with how slow my Terminal (in my case iTerm2) starts up. It would take 5-10 seconds before I was presented a prompt. Being in the console for the better part of the day, this was unacceptable.
The first thing I did was upgrade Bash to Zsh. I’d heard great things about Zsh, so I thought I’d give it a try. Zsh is really awesome, but it did not fix the start-up delay I was experiencing previously with Bash.
Doing a little digging around I found a working solution. Apparently Apple keeps system logs in /private/var/log/asl/*.asl. Removing these files made my shell fast again.
Do not remove all files in /private/var/log/asl as there are other files there that are not related to the shell. Leave them in there.
With the above warning in the back of your mind, open your terminal (slowly) and issue the following command:
sudo rm /private/var/log/asl/*.asl
Now quit and restart Terminal or iTerm2 and your prompt should present itself quickly again.