With proper syntax explain the use of chmod command.

File and directory permissions can only be modified by their owners, or by the superuser (root),by using the chmod system utility.
chmod (change [file or directory] mode) 
$ chmod options files
 
chmod accepts options in two forms. Firstly, permissions may be specified as a sequence of 3 octal digits (octal is like decimal except that the digit range is 0 to 7 instead of 0 to 9). Each octal digit represents the access permissions for the user/owner, group and others respectively. The mappings of permissions onto their corresponding octal digits is as follows:
 
For example the command: 
                                                                 $ chmod 600 private.txt 
 
sets the permissions on private.txt to rw------- (i.e. only the owner can read and write to the file). Permissions may be specified symbolically, using the symbols u (user), g (group), o (other), a (all), r (read), w (write), x (execute), + (add permission), – (take away permission) and = (assign permission). 
For example, the command: 
                                                      $ chmod ug=rw,o-rw,a-x *.txt
 
 sets the permissions on all files ending in *.txt to rw-rw---- (i.e. the owner and users in the file's group can read and write to the file, while the general public do not have any sort of access).chmod also supports a -R option which can be used to recursively modify file permissions, e.g.
                                          $ chmod -R go+r play 

will grant group and other read rights to the directory play and all of the files and directories within play.
chgrp (change group) 
$ chgrp group files 
can be used to change the group that a file or directory belongs to. It also supports a -R option.

 
With proper syntax explain the use of chmod command. With proper syntax explain the use of chmod command. Reviewed by enakta13 on November 11, 2012 Rating: 5

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