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chmod: |-
chmod: a Unix utility for managing file permissions
Modes can be expressed in octal or human-readable:
Description | Octal | Human-readable
Set user write | 200 | u=w
Set user rwx, group and others rx | 755 | u=rwx,go=rx
Add group read | - | g+w
Remove all execute | 111 | a-x
Set user rws, everyone else none | 4700 | u=rwxs,go-rwx
Add user sticky | - | u+s
Add group sticky | - | g+s
With three-digit octal notation, each numeral represents a different component of the permission set: user class, group class, and "others" class respectively.
Each of these digits is the sum of its component bits. As a result, specific bits add to the sum as it is represented by a numeral:
* The read bit adds 4 to its total,
* The write bit adds 2 to its total,
* The execute bit adds 1 to its total.
"-rwxr-xr-x" would be represented as 755 in three-digit octal.
"-rw-rw-r--" would be represented as 664 in three-digit octal.
"-r-x------" would be represented as 500 in three-digit octal.
Example: Make foo u=rwx and go=rx:
$ chmod u=rwx,go=rx foo
Example: Make foo u=rwx and go=rx (in octal):
$ chmod 755 foo
Example: Find all subdirectories, put them in 'mygroup', make them group sticky:
$ find . -type d -exec chgrp mygroup \{\} \;
$ find . -type d -exec chmod g+s \{\} \;
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