Why does umask have 4 digits

Full permission for any directory is considered and for any file which acts as the base permission for calculation umask value for directory and file respectively. The first digit in 0 defines the special permission value. To understand the difference between. Save my name, email, and website in this browser for the next time I comment.

What is umask value? What is default umask value? From man 2 umask , i. The umask is not simply substracted, but is processed bitwise. Bits set in the umask are cleared in the resulting file mode. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more.

What is the first digit in umask value? Asked 4 years, 8 months ago. Active 4 years, 8 months ago. Viewed 11k times. Improve this question. Philip Kirkbride Philip Kirkbride 8, 19 19 gold badges 81 81 silver badges bronze badges. Maybe my understanding of how this works is completely off. Each of these three numbers is, in turn, formed as a 3-digit binary number where the first digit is the read permission, the second is the write permission, and the third digit is the execute permission.

Unlike the chmod command, however, in each binary digit of the umask, a 0 indicates that the permission is given, a 1 that the permission is denied. I the owner have permission to read, write and execute my own files. The group to which a file belongs has , permission to read, no permission to write, and permission to execute that file.

The rest of the world has , no permission to read, write or execute. Ask Question. Asked 9 years, 10 months ago. Active 19 days ago. Viewed 24k times. Improve this question. Steven T. Snyder Steven T. Snyder 2 2 gold badges 9 9 silver badges 19 19 bronze badges. Add a comment. Active Oldest Votes. From man chmod : A numeric mode is from one to four octal digits , derived by adding up the bits with values 4, 2, and 1. What are "set user ID", "set group ID", and "sticky", you ask?

And sticky : The most common use of the sticky bit today is on directories. Improve this answer. Handyman5 Handyman5 4, 23 23 silver badges 30 30 bronze badges. Setgid has another very important function that I rely on daily but which is not included in Handyman5's excerpt the quote is from the same page linked above : The setuid and setgid flags, when set on a directory, have an entirely different meaning.