liunx chmod command

Linux / Unix chmod command Quick links About chmod Syntax Examples Additional information Related commands Linux / Unix main page About chmod Changes the permission of a file. Syntax chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... -c, --changes like verbose but report only when a change is made --no-preserve-root do not treat `/' specially (the default) --preserve-root fail to operate recursively on `/' -f, --silent, --quiet suppress most error messages -v, verbose output a diagnostic for every file processed --reference=RFILE use RFILE's mode instead of MODE values -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Permissions u - User who owns the file. g - Group that owns the file. o - Other. a - All. r - Read the file. w - Write or edit the file. x - Execute or run the file as a program. Numeric Permissions: CHMOD can also to attributed by using Numeric Permissions: 400 read by owner 040 read by group 004 read by anybody (other) 200 write by owner 020 write by group 002 write by anybody 100 execute by owner 010 execute by group 001 execute by anybody Examples The above numeric permissions can be added to set a certain permission, for example, a common HTML file on a Unix server to be only viewed over the Internet would be: chmod 644 file.htm This gives the file read/write by the owner and only read by everyone else (-rw-r--r--). Files such as scripts that need to be executed need more permissions. Below is another example of a common permission given to scripts. chmod 755 file.cgi This would be the following 400+040+004+200+100+010+001 = 755 where you are giving all the rights except the capability for anyone to write to the file.cgi file(-rwxr-xr-x). Finally, another common CHMOD permission is 666, as shown below, which is read and write by everyone. chmod 666 file.txt Additional information Below is an example of how a file may be listed when typing ( ls -l ) at the prompt as well as information on how to interpret it. -rw-rw-r-- 1   hope  123   Feb 03 15:36   file.txt - rw rw- r-- 1 hope 123 Feb 03 15:36 file.txt File owner group everyone else links owner size mod date file name