How do I edit a plist file in Terminal

is this the file /system/library/coreservices/SystemVersion.plist?
why do you want to change it? be very careful with this file. it may seem innocuous to change it but it can also may make your system unbootable. this happened to a lot of people with this file a while back after 10.5.2 update. apple released another update (airport I think) that change the build number and made it impossible to reinstall 10.5.2 combo update without tinkering with this file. this was only really resolved when 10.5.3 came out.

Message was edited by: V.K.

Airsculpture wrote:
Oh I see.

The reason is I have a firmware update for the DVD drive but it won't work on my current OS version. I saw on a forum that someone had altered this file so the two numbers in it were 10.4.9, installed the firmware update and altered them back.

hmm. this all sounds pretty strange. firmware update should be applicable no matter what the OS if it's really needed. you can try it if you wish but back up first.
Király gave you the correct instructions but you need to do it with sudo. so enter

sudo nano /system/library/coreservices/SystemVersion.plist

in terminal. authenticate with your admin password. edit the file and save.

You might find it easier to use TextEdit.

1. Use Finder to go to /System/Library/CoreServices.
2. Drag the SystemVersion.plist file to the Desktop to make a copy of it.
3. Repeat step two to make a second copy of the file.
4. Edit the first copy you made with TextEdit. Save it back to the Desktop.
5. Drag the edited file back to /System/Library/CoreServices.
6. Answer "yes" when it asks you if you want to overwrite.
7. Repair permissions with Disk Utility.

When you want to put everything back, replace the edited copy with the second copy you made in step 3. Repair permissions with Disk Utility.

Unix forum:
http://discussions.apple.com/forum.jspa?forumID=735

I like the nano editor. Open Terminal, type:

nano (hit spacebar, drag the .plist file into the Terminal window, press return)

Press control-X when done.

after you edit the file enter control+X and confirm that you are saving to the correct file. is this what you are doing?