[Griffter]

A decker has entered a host and needs to find a certain file--let's say it's Joe Wageslave's HR file.  He doesn't know its contents (which is why he's looking for, natch), but he knows the guy's name and the type of file it is.  The file isn't silent.  Would he roll perception or search to find it?

[Whiskeyjack]

I'd say Matrix Search.

Search is like Googling - you're trying to find information (even hidden or obscure information on a fortified host). Matrix Search is, in part, how you do legwork on the Matrix as well.

Matrix Perception is for spotting or analyzing specific icons.

So you'd use Matrix Search to find the file in the host, and then Matrix Perception to analyze and see if it has a Data Bomb on it.

[ZeConster]

Huh - you're the second person from the Shadowrun Universe forums to discuss something both here and there in as many days. Noblejohn hadn't gotten an answer yet when he posted here, so I can understand that, but were you unsatisfied with the discussion there?

Anyway, I'm going through the matrix chapter right now: I'll edit my post once I'm done.

• The page 224 example mentions a hacker "flipping through her music collection in a little virtual window" and "seeing an album he likes", which implies locating files works the same way as with, say, Windows Explorer - this might just be a Matrix Perception thing, though.
• The page 232 example says "The target isn’t running silent, so he can see the file he wants" - however, this may just mean he'd have to do a Matrix Perception check on the commlink to notice it and any files on it if the commlink were running silent.
• The page 235 sidebar mentions that Matrix Perception can tell you "the most recent edit date of a file", "the presence of a data bomb on a file", "the type of icon", "whether a file is protected" - however, none of these things are "the file's contents" - however however, the page 224 example shows the hacker recognizing a specific album, so chances are there's text or something - however however however, the page 224 example doesn't actually mention him doing a Matrix Perception check - however however however however, page 235 does mention Matrix Perception can be used to "spot a target icon you're looking for".
• Matrix Search just says it allows you to find "information about a topic", and if a file is Protected, Matrix Search doesn't actually help you find the contents.

So all in all, I guess my answer is "either, I guess, or both?". Matrix Perception could help you notice the file if you know exactly what to look for (there'll probably be a lot of files, though, so you'll have to have pretty specific knowledge), while Matrix Search could either find the file location or give you the information you need to make said Matrix Perception test. Since the page 235 sidebar says you need Matrix Perception to tell what type of icon you're dealing with, we at least know you can't just scroll through all the files without Matrix Perception, which means the page 224 example probably involved making Matrix Perception checks on all the icons.
EDIT preemptive EDIT: I guess Xenon's found the exact rule.

[Xenon]

Matrix Search with a base time of 1 minute.

SR5 p. 241 Matrix Search
...Some information is protected and kept secret, stored in a host that is not publicly accessible. Finding this information usually requires you to find and enter the hosts in which the data is hidden. You can then make a Matrix Search within the host, using a base time of 1 minute (regardless of the kind of information you’re looking for). This only works if the information is at least occasionally accessed by the legitimate users of the host. If the information is archived, you’ll need to dig deeper into the host for that information, a dangerous process that is detailed in the forthcoming Matrix sourcebook.

[Griffter]

Matrix Search with a base time of 1 minute.

SR5 p. 241 Matrix Search
...Some information is protected and kept secret, stored in a host that is not publicly accessible. Finding this information usually requires you to find and enter the hosts in which the data is hidden. You can then make a Matrix Search within the host, using a base time of 1 minute (regardless of the kind of information you’re looking for). This only works if the information is at least occasionally accessed by the legitimate users of the host. If the information is archived, you’ll need to dig deeper into the host for that information, a dangerous process that is detailed in the forthcoming Matrix sourcebook.

Cool, thanks for the citation!