UNIX for Dummies Questions & Answers

What characters can't be used with a mkdir? Any limits on length of name?

Thank you,

Randy M. Zeitman
http://www.StoneRoseDesign.com

All your answers are in the man pages.

I don't know what that means...what's "in the man"? if by chance you mean a book I have four and none list the answer. I've also tried numerous Yahoo searches.

that means that after you login,

give the following command on the shell prompt

man mkdir

Sorry flignar thought you knew what manual pages were.
Just do as asifraj says. Go to a console type in man mkdir, or anything else you may wish to have explained; typing man man, will give you a rundown on what manual pages are all about.

You might find man -k <keyword> useful too.
(where <keyword> is a word of your choosing )

This lets you put in a keyword like 'directory' and find what man pages are available for it. Handy if you don't know the command name you want to read about.

I did a "man mkdir" and I didn't find an answer to these questions.

The mkdir() system call code in the kernel does not directly impose a limit on the length of a filename. However it must talk to the code for filesystem and this will impose a limit. What that limit is depends on the file system. Posix will guarantee at least 14 characters. To be posix compliant, a unix system must allow at least that much. HP-UX still supports the "short filename" option. If you choose, you can make HP-UX enforce a 14 character limit. This is rarely done. The most common limit these days is 255 characters for a filename. And the most common limit for a full path name is 1023.

You probably will find that you have a pathconf() system call that can determine your exact limit. Note that you must give pathconf() a file name because the limits can vary from filesystem to filesystem.

Because a slash is used to separate the components of a pathname, a slash cannot be used inside a component. And binary zero is used to terminate a string. So no binary zeros either. Any other byte value is fair game as far as the kernel is concerned. A filename with an embedded carriage return will cause you nasty problems. And you really will be better off if you limit yourself to printable characters.