chmod [Command]

Command chmod

chmod – command changes the permissions of one or more files.


chmod [-cfvR] permissions files


-c displays only files with changed permissions.
-f suppress error messages.
-v displays detailed information about changes of access rights.
-R recursively changes the permissions of files in all subdirectories.


To effectively use chmod to know how to set permissions. One ways involves a concatenation of one letter from each of the following tables consecutively (Who / Action / Access):

Who Action Access
u user + add r read
g group delete w write
o others = assign x execute
a all s set user ID

To grant read access to all files in directory, type chmod a+r *. For permit the execution of the file to all users, type chmod + x filename.

Another way to specify permissions is to use sequence CONTRACT PERIOD three octal digits. In a detailed listing of the right to read, write and execute for user, group and others look like a sequence rwxrwxrwx (with a dash in place of letters for prohibited transactions). Row rwxrwxrwx can be regarded as a three-fold repetition of the line rwx. Now set the value r = 4, w = 2 and x = 1. To obtain the sequence rwx, add the values r, w and x. Thus, rwx = 7. Using this formula, you can assign three-digit value of any rights of access.

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