Programming Perl, 4th Edition

mkdir

mkdir FILENAME, MASK
mkdir FILENAME

This function creates the directory specified by FILENAME, giving it permissions specified by the numeric MASK as modified by the current umask. If the operation succeeds, it returns true; otherwise, it returns false.

If MASK is omitted, a mask of 0777 is assumed, which is almost always what you want anyway. In general, creating directories with permissive MASKs (like 0777) and letting the user modify that with her umask is better than supplying a restrictive MASK and giving the user no way to be more permissive. The exception to this rule is when the file or directory should be kept private (mail files, for instance). See umask.

If the mkdir(2) syscall is not built into your C library, Perl emulates it by calling the mkdir(1) program for each directory. If you are creating a long list of directories on such a system, it’ll be more efficient to call the mkdir program yourself with the list of directories than to start zillions of subprocesses.