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Quick links About
chmod
Syntax
Examples
Additional information
Related commands
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...
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-c, --changes |
like verbose but report only
when a change is made |
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--no-preserve-root |
do not treat `/' specially (the
default) |
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--preserve-root |
fail to operate recursively on
`/' |
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-f, --silent, --quiet |
suppress most error messages |
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-v, verbose |
output a diagnostic for every
file processed |
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--reference=RFILE |
use RFILE's mode instead of MODE
values |
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-R, --recursive |
change files and directories
recursively |
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--help |
display this help and exit |
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--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+020+100+010+001 = 775 where
you are giving all the rights but the capability for anyone to edit your file.cgi
(-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 |
Related commands
chown
getfacl
ls
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