Umask in linux

Umask in linux-general Linux technology-Linux programming and kernel information. For details, refer to the following section. During the linux lab this week, many people asked me how to use umask. Here I will explain it.

A permission mask umask
Umask is supported by chmod. It has a total of four bits (gid/uid, owner, group permission, and permissions of other users), but the last three are usually used, for example, if you use chmod 755 file (the permission for this file is Master read (4) + write (2) + execute (1), the same group and other users have read and write permissions)

Role of binary umask
By default, the umask value is 022 (which can be viewed using the umask command). The default permission for the created file is 644 (6---2 ), the default permission for the Created directory is 755 (7---2). You can use ls-l to verify it. Now you should know the usage of umask, it is used to control the default permissions. Do not assign full permissions to the default files and directories.

3. Modify umask value
After learning about the role of umask, you can modify the value of umask. For example, umask 024 will grant the default permission to files and directories created later to 642,753.

Iv. Save the umask value to the Environment File
To change the umask value for a long time, you can write it into/etc/profile or ~ /. Profile or ~ /. Bash_profile, you should know what these files are.