Entry
Linux: Permission: Get: How check current read/write/copy permissions? [device / chmod / file]
Feb 26th, 2004 20:30
Knud van Eeden,
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--- Knud van Eeden --- 18 September 2003 - 00:36 pm ------------------
Linux: Permission: Get: How check current read/write/copy permissions?
[device / chmod / file]
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In general:
---
in case of a file, you can check the currently permission settings, by
typing the command:
ls -l <your filename>
---
in case of a directory, you can check the currently permission
settings, by
typing the command:
ls -l <your directory>
---
in case of a device (which is by design also represented as a file),
you can check the currently permission settings, by typing the command:
ls -l <your device>
---
---
e.g.
To check the current permission settings of the file 'ddd.c', type the
command on the console command line:
ls -l ddd.c
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a typical result from this is showing the current
permissions for this file
-rw-r--r-- 1 root root 11, 57 Dec 3 10:19 ddd.c
---
---
e.g.
To check the current permission settings of the (executable) file
'a.out', type the command on the console command line:
ls -l a.out
---
a typical result from this is showing the current
permissions for this file
-rwxr-xr-x 1 root root 11540 Dec 3 11.50 a.out
---
---
e.g.
To check the current permission settings of the directory
'/home', type the command on the console command line:
ls -l /home
---
a typical result from this is showing the current
permissions for this directory
drwx------ 13 john john 4096 Dec 3 14.29 a.out
---
---
e.g.
To check the current permission settings of the SCSI diskdrive 'scd0',
type the command on the console command line:
ls -l /dev/scd0
---
a typical result from this is showing the current
permissions for this SCSI disk:
brw------ 1 root disk 11, 0 Jan 30 2003 scd0
---
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How could this be interpreted?
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If you look at the general scheme below, it shows
that:
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1. The first bit is 'b', or thus 'B'inary or thus
a device
---
2. The second bit is 'r', or thus 'R'ead.
Thus you have 'r', or thus read permission to the
directory where this file 'scd0' is stored
(by default the '/dev' directory).
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2. The third bit is 'w', or thus 'W'rite.
Thus you have write permission.
---
3. There exists 1 link for this file
---
4. The login name is 'root'
---
---
+-> total amount of links for this file
| +-> login name of the owner / creator
| | +-> total amount of bytes
| | | for this file
| | | +-> creation date
| | | | +-> creation time
| | | | | +-> name for it
| | | | | |
1 2 3 4 5 6 7 8 9 10 | | | | | |
- r w - r - - r - - 1 myself 182 Nov 11 15:25 myfile.dok
bit1 = directory (file is directory or not)
---
bit2 = read permission owner
bit3 = write permission owner
bit4 = execute (or copy) permission owner
bit5 = read permission for the other members in same group
bit6 = write permission for the other members in same group
bit7 = execute (or copy) permission for the other members in same group
bit8 = read permission for the other members in all other groups
bit9 = write permission for the other members in all other groups
bit10 = execute (or copy) permission for the other members in all
other groups
---
d = directory
b = device
---
r = read permission
w = write permission
x = execute permission
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[book: see also: Brown, P. J. - begin with Unix - ISBN: 90-6789-026-X -
p. 64]
---
---
Note:
Conversion to the chmod value:
As you might want to know quickly what the chmod 3 digit value is, you
can add the 4, 2 and 1 values of the three corresponding groups.
---
e.g.
1 2 3 4 5 6 7 8 9 10
- r w - r - - r - -
or thus replacing by zeros and ones:
0 1 1 0 1 0 0 1 0 0
with corresponding values:
4 2 1 4 2 1 4 2 1
so looking only at the values with a '1',
and adding these for each group, this becomes:
4+2+0 4+0+0 4+0+0
or thus:
6 4 4
So the chmod value of this file is 644.
So if you should have typed:
chmod 644 yourfilename
it should show the same values, after doing
a
ls -l yourfilename
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Tested in Linux Red Hat v9
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Internet: see also:
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Linux: Permission: View: How to view your read/write/copy permissions?
[scd0 / chmod]
http://www.faqts.com/knowledge_base/view.phtml/aid/24428/fid/107
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Linux: File: Permission: Set: How to set your read/write/execute
permissions? [chmod / run]
http://www.faqts.com/knowledge_base/view.phtml/aid/24443/fid/107
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C++: Compile: Operating system: Linux: How to compile C or C++ program
on Linux? [run / hello world]
http://www.faqts.com/knowledge_base/view.phtml/aid/26744/fid/107
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