Advanced Programming in the UNIX Environment: Week 03, Segment 5 - umask(2)

In this video lecture, we'll take a look at what file ownership and permissions are applied when we create a new file. In the process, we'll learn about the concept of a process's "umask", and look at how the 'umask' shell built-in is implemented.

Outline:
00:00 Introduction
00:20 Ownership of files
03:58 umask(2)
04:36 umask(2) example
07:08 Recap

[SamWhitlock]

I haven't seen this in the wild, but I imagine it would be very useful to support some POSIX-compliant legacy system (that assumes this BSD behavior) that used to run on a BSD variant and is moved to Linux.

[hts]

I have spent several days writing the ls command with c but find it very hard to implement, i also have a look at the ls src code and find it has more 4000 lines of code.. so can i ask how i can start to write ls code in a right way?