Validate the user name in Unix/Solaris

Question

Is there any C API for validating user name ?

I am taking input of user_name which might not be present at that point in time. Since the user name needs to follow POSIX rules, is there any C API which can do the validation?

See also the following question: stackoverflow.com/questions/6949667/… — Rory Hunter
– Rory Hunter, Commented Apr 5, 2012 at 10:23

Perry · Accepted Answer · 2012-04-05 18:22:05Z

1

I presume you are trying to figure out whether a user name exists on the system you are running on. For that, you are looking for getwpent()/getpwnam() -- check the manual page for details.

Although these return more information than you want, getpwnam() will also (easily) tell you if there is or isn't a password file entry corresponding to a given user name.

(If you are simply looking to make sure a user name contains only valid characters, just make sure it only contains [A-Za-z0-9_]+)

answered Apr 5, 2012 at 18:22

Perry

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2 Comments

Jonathan Leffler Over a year ago

The user name should probably not be pure numeric; at the least, you can expect confusion if the user name looks like a number (doubly so if the UID is not the same number as the name — yes, you can do it; no, you should not do it!).

Perry Over a year ago

Yes, that's true. I suppose the right regexp is [A-Za-z_][A-Za-z_0-9]*

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