why do I need .zshrc?

On my MacBook Air, I needed a .zshrc file to convince the machine to use my selected terminal prompt (e.g. export PS1="prompt"). On my iMac, I didn't need that. The terminal prompt was somehow already correct. But I have .bashrc files on both machines, and they do a fine job with maintaining system aliases. Both machines are on Sequoia 15.3.2. I am told that Macs REALLY want to use .zshrc. Why? Do I just move all my .bashrc commands over to .zshrc and kill off .bashrc? Are my .bashrc files eventually just going to stop working?

iMac 24″, macOS 15.3

Posted on Mar 30, 2025 7:53 AM

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g_wolfman

Level 4

3,472 points

Posted on Mar 30, 2025 9:34 AM

One machine (iMac) was older and using Bash originally - it would have to be manually switched to Zsh. The other (Air) is newer and had Zsh as the default shell out of the box.

But no, do not simply use mv to change the .bashrc file to .zshrc. The two don't use the same syntax for everything and if you do that you may have lines in .bashrc that will cause Zsh to experience a fatal error and crash. And if you use third party apps like iTerm instead of Terminal - and installed the Shell Integrations - then there will be non fatal but incompatible lines and it'll be errors everywhere.

I recommend that you review your .bashrc file and copy the right lines into a new .zshrc file.

Or...wild thought...there's also an opportunity here for you to really dig into shell customization with Oh My Zsh and its many themes: https://ohmyz.sh/

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19 replies

Dannymac22 Author

Level 2

206 points

Mar 30, 2025 4:52 PM in response to MrHoffman

OK, so then if the default is account-specific, that's why Migration Assistant preserved it. To the extent that bash and zsh are not wholly compatible, I guess that makes sense that Apple would leave it up to the user to make the change. In my case, they were wholly compatible.

g_wolfman

Level 4

3,472 points

Mar 30, 2025 9:52 AM in response to Dannymac22

Oh, in that case why not just edit the .zshrc file and insert the "export PS" command you want - are you familiar enough with vim, nano or pico to do that?

Dannymac22 Author

Level 2

206 points

Mar 30, 2025 3:58 PM in response to g_wolfman

Wrong. As I've said repeatedly, I have PRECISELY the same OS on two machines, and on one bash is default, and on the other zsh is default. Read harder.

g_wolfman

Level 4

3,472 points

Mar 31, 2025 4:00 PM in response to Dannymac22

Yes, an older computer that had its contents migrated by Migration Assistant would have the same effect, as MrHoffman expanded upon.

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why do I need .zshrc?