Change Mode

What Does Change Mode Mean?

Change mode (chmod) is a Unix operating system command used by administrators and programmers to set or change the access permissions of a file or directory. These settings determine the level of access to be granted to the given file or directory.

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The chmod command was first used in ATT Unix 1 and is still in use today by Unix-like operating systems. It is also available as a C language library function in Unix.

Techopedia Explains Change Mode

The syntax for change mode is as follows:

chmod [OPTIONS]… MODE[,MODE]… FILENAME1 [,FILENAME2]…
chmod [OPTION]… OCTAL-MODE FILENAME1 [,FILENAME2]…
chmod [OPTION]… [REFERENCE] [OPERATOR] [MODES] FILENAME1 [,FILENAME2]..

The chmod command has the following options:

-R, –recursive: Changes the directories and files recursively
-v, –verbose: Displays a diagnostic report for every processed file
-c, –changes: Like verbose but displays only when there are actual changes
-f, –silent:Suppress error messages
–reference=RFILE: Use RFILE’s mode instead of MODE values

Permissions are granted as follows: a: All
o: Other
g: Group
r: Read
u: User
w: Write
x: Execute or run as a program

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.