Getting file permissions in 'NNN' mode

[Miguel Cuesta]

Hi!

I want to obtain a file's permission in 'NNN' mode, not
in '-rwxrwxrwx' mode.

I mean, I would like a script to get DIRECTLY '666' from
a file, not '-rw-rw-rw'.

Any help?

[linuxfan]

Hi Miquel,


I am not aware of any way to directly obtain the permissions in "octal format"

One of the ways you can do is put in a case statement in your script and convert the permissions to octal format.

Eg:
perm=`ls -al file | awk '{print $1}'

case $perm in
-rwxrwxrwx)
PERM=777 ;;
-rw-rw-rw-)
PERM=666 ;;
esac

Include all the permissions in the case statement. I am sure there is an easier way, just can't think of one right now.

-Ramesh

[Santosh Nair_1]

Miguel,

I assume you're trying to get these permissions so that you can set permissions on some other file via a script? If that's the case, you should be able to use the octal values directly, i.e. you should be able to do chmod u=rw,g=rw,o=rw file.
This could be done using cut and sed, i.e something like:

PERM="-rw-rw-rw-"
UPERM=$(echo $PERM|cut -c2-4|sed s/\-//g|sed s/s/xs/g)
GPERM=$(echo $PERM|cut -c5-7|sed s/\-//g|sed s/s/xs/g)
OPERM=$(echo $PERM|cut -c8-10|sed s/\-//g|sed s/s/xs/g)

chmod u=$UPERM,g=$GPERM,o=$OPERM file.

Hope this helps.

-Santosh

[A. Clay Stephenson]

Hi Miguel:

Here is a 30 second perl script to do what you want:

#!/usr/bin/perl

$i = 0;
while ($i <= $#ARGV)
{
($dev,$ino,$mode) = stat($ARGV[$i]);
printf("%s\t%03o\n",$ARGV[$i],$mode & 0777);
++$i;
}

After making it executable, run it like this:
omode.pl myfile1 myfile2 myfile3
to produce this output:
myfile1 750
myfile2 400
myfile3 664

That should do it, Clay

[Darrell Allen]

Nice script Clay. Can you show the mod for files with sticky or suid bits?

Darrell

[A. Clay Stephenson]

Hi Darrell:

Easy as pie; we just mask off 3 less bits and expand the output field to 4 octal digits:

#!/usr/bin/perl

$i = 0;
while ($i <= $#ARGV)
{
($dev,$ino,$mode) = stat($ARGV[$i]);
printf("%s\t%04o\n",$ARGV[$i],$mode & 07777);
++$i;
}

That should do it with the setuid, setgid, & sticky bits displayed in the leftmost digits.

Another variation on the theme is to not mask anything and expand the octal field to reveal file type (regular, directory, fifo, ...) as well.

#!/usr/bin/perl

$i = 0;
while ($i <= $#ARGV)
{
($dev,$ino,$mode) = stat($ARGV[$i]);
printf("%s\t%08o\n",$ARGV[$i],$mode);
++$i;
}

Regards, Clay

[James R. Ferguson]

Hi:

Here's a shell script to return the octal numeric mode of the file passed to it. The script handles the setuid, setgid and sticky bits along with the standard permissions:

#!/usr/bin/sh
#
typeset -i PERMFCT=0 #...permission mode factor
typeset -i MISCFCT=0 #...miscellaneous mode factor
typeset -i BITSNBR=2 #...bit number (1-relative)
typeset -i BITSVAL=0 #...simple bit value
typeset -i OCTMODE=0 #...final, octal numeric mode
#
[ "$#" != 1 ] && { echo "Usage: $0 file"; exit 1 ; }

SMODE=`ls -l $1|awk '{print $1}`
#
while (( BITSNBR <= 10 ))
do
case `expr \( $BITSNBR - 2 \) / 3` in #...establish weighted values...
0 ) PERMFCT=100
MISCFCT=4000
;;
1 ) PERMFCT=10
MISCFCT=2000
;;
2 ) PERMFCT=1
;;
esac
#
case `expr substr $SMODE $BITSNBR 1` in
r ) BITSVAL=4
MISCFCT=0
;;
w ) BITSVAL=2
MISCFCT=0
;;
x ) BITSVAL=1
MISCFCT=0
;;
s|t )
BITSVAL=1
;;
S|T )
BITSVAL=0
;;
* ) BITSVAL=0
MISCFCT=0
;;
esac
#
OCTMODE=`expr $PERMFCT \* $BITSVAL + $MISCFCT + $OCTMODE`
#
let BITSNBR=$BITSNBR+1
done
#
echo "mode = $OCTMODE"
exit 0
#
#.jrf.

Regards!

...JRF...

[James R. Ferguson]

Hi:

>>> Corrected Copy <<<
----------------------

Here's a shell script to return the octal numeric mode of the file passed to it. The script handles the setuid, setgid and sticky bits along with the standard permissions:

#!/usr/bin/sh
#
typeset -i PERMFCT=0 #...permission mode factor
typeset -i MISCFCT=0 #...miscellaneous mode factor
typeset -i BITSNBR=2 #...bit number (1-relative)
typeset -i BITSVAL=0 #...simple bit value
typeset -i OCTMODE=0 #...final, octal numeric mode
#
[ "$#" != 1 ] && { echo "Usage: $0 file"; exit 1 ; }
#
SMODE=`ls -l $1|awk '{print $1}`
#
while (( BITSNBR <= 10 ))
do
case `expr \( $BITSNBR - 2 \) / 3` in #...establish weighted values...
0 ) PERMFCT=100
MISCFCT=4000
;;
1 ) PERMFCT=10
MISCFCT=2000
;;
2 ) PERMFCT=1
MISCFCT=1000
;;
esac
#
case `expr substr $SMODE $BITSNBR 1` in
r ) BITSVAL=4
MISCFCT=0
;;
w ) BITSVAL=2
MISCFCT=0
;;
x ) BITSVAL=1
MISCFCT=0
;;
s|t )
BITSVAL=1
;;
S|T )
BITSVAL=0
;;
* ) BITSVAL=0
MISCFCT=0
;;
esac
#
OCTMODE=`expr $PERMFCT \* $BITSVAL + $MISCFCT + $OCTMODE`
#
let BITSNBR=$BITSNBR+1
done
#
echo "mode = $OCTMODE"
exit 0
#
#.jrf.

Regards!

...JRF...

[Frank Slootweg]

Kind of a hack and slow for large files (because the file is read completely):

echo local/bin/procmail | cpio -oB | cpio -iBtv

To get only the last three mode 'digits' (and no "... blocks" messages):

echo file | cpio -oB 2> /dev/null | cpio -iBtv 2>/dev/null | cut -c4-6

[Robin Wakefield]

Hi Miquel,

Here's an awk way of doing it for 000-777 modes:

#!/bin/sh

ls -l $* | awk '
{
x=0
for (i=2;i<11;i++){
n=int((10-i)/3)
if (substr($1,i,1) == "r")
x=x+10**n*4
if (substr($1,i,1) == "w")
x=x+10**n*2
if (substr($1,i,1) == "x")
x=x+10**n*1
}
print x,$NF
}'

Rgds, Robin

[Joseph C. Denman]

You guys are GOOD!!!!


...jcd...

[Paul Winchcombe]

Great code guys!

I've been wresteling with the same problem for a while now and found solutions using awk, sed, case and now perl.

By far the best performance is Perl (no supprise there then) but the problem is I have a list of directories in which all files should be a certan permission, eg 500. But using a find directed into the above Perl example caused a 'fork-exec' for each file and multiplies the runtime by 100's.

Can the find be done from within the Perl?

[Carlos Fernandez Riera]

My own way:

sperm=$(echo "prwxrw-r--" | tr "pcbrwx-" "0001110");
let operm=2#${sperm}
printf "chmod %o %s \n" $operm $sperm

[Carlos Fernandez Riera]

Paul:

It is the same stone at every place.

I am thinking about the use of coprocesess!!!to resolve this multi exec.

[Paul Winchcombe]

Carlos,

Thanks, I like the use of 'tr' as it's quick but I could not think of a method for SUID, SGID and sticky bits as well???

[Carlos Fernandez Riera]

Hi again Paul:

Yes i know by this way it is easy to treat SUID and others. I want to check lvols over MC/SG systems and their owner and permision. To do this tr is enought.
I wrote to you because you and me run sar -ucb whilest running our procedures, and it true that forks and execs growth up to infinty.

I use to write ksh script, and i think it could be treated with ${var%[rwxS]} funcionality, to reduce tr and printf forks, and coprocess to manage ll. This is the way i will take.



If you like to write me : carlosfriera@navegalia.com

Regards.