Script for removing semaphores and shared memory
Zinger
I have written a shell script that removes semaphores and shared
memory as follows. The script works fine.
Can this be written with any less number of lines?
Thanks in advance
=====================================================================
user=`whoami`
sems=`ipcs -s|grep $user| awk '{print $2}'`
shmem=`ipcs -m|grep $user| awk '{print $2}'`
count=0
for semaphore in $sems
do
ipcrm -s $semaphore
((count=count+1))
done
echo "$count semaphores for $user removed"
count=0
for sharedmem in $shmem
do
ipcrm -m $sharedmem
((count=count+1))
done
echo "$count shmem for $user removed"
=====================================
Icarus Sparry
Obviously it can, just replace all but the last newline character with a
semicolon.
You can reduce the number of processes by some transformations
grep $user | awk '{print $2}' --> awk "/$user/ { print \$2 }"
(assuming that $user has no / characters in it)
As ipcrm can remove more than one thing at a time, and you are not going
to be hitting size limits
user=$(whoami)
set -- $(ipcs -s | awk "/$user/ { print \$2}")
if [ $# -gt 0 ] ; then
ipcrm -s "$@"
fi
echo $# semaphores for $user removed
set -- $(ipcs -m | awk "/$user/ { print \$2}")
if [ $# -gt 0 ] ; then
ipcrm -m "$@"
fi
echo $# shmem for $user removed
If say you have 10 semaphores and no shared memory segments the original
script will use 17 processes, and the new one will use 6 (this assume a
good modern shell implementation).
Seebs
> I have written a shell script that removes semaphores and shared
> memory as follows. The script works fine.
Congratulations!
> Can this be written with any less number of lines?
Almost certainly, but I don't think that should be viewed as a
primary goal.
> user=`whoami`
> sems=`ipcs -s|grep $user| awk '{print $2}'`
> shmem=`ipcs -m|grep $user| awk '{print $2}'`
Consider:
sems=$(ipcs -s | awk '$5 == "'"$user"'" { print $2 }'`
I may have the quoting wrong, but the intent is to have awk do the
check directly. Consider what happens, otherwise, if you have a user
named 'heel' and a semaphore owned by group 'wheel'.
Note that you might still have issues for some possible boundaries.
So consider:
'/^Shared Memory/ { x = 1 } x && $5 == "'"$user"'" { print $2 }'
as the awk script for the shmem case.
> count=0
> for semaphore in $sems
> do
> ipcrm -s $semaphore
> ((count=count+1))
> done
> echo "$count semaphores for $user removed"
This can be simplified.
set -- $sems
printf "Removing %d semaphores for %s:\n" "$#" "$user"
for semaphore; do
ipcrm -s $semaphore
done
Note that you are not checking for failures from ipcrm, which you
should be. I would probably do:
set -- $sems
failed=0
printf "Removing %d semaphores for %s:\n" "$#" "$user"
for semaphore; do
ipcrm -s $semaphore || failed=`expr $failed + 1`
done
if [ $failed -ne 0 ]; then
printf >&2 "%d error(s).\n" "$failed"
fi
Remember, fewer lines isn't as important as handling errors and
unexpected inputs.
-s
--
Copyright 2010, all wrongs reversed. Peter Seebach / usenet...@seebs.net
http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures
http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
I am not speaking for my employer, although they do rent some of my opinions.
Janis Papanagnou
> On 2011-01-08, Zinger <zma...@gmail.com> wrote:
>> I have written a shell script that removes semaphores and shared
>> memory as follows. The script works fine.
>
> Congratulations!
>
>> Can this be written with any less number of lines?
>
> Almost certainly, but I don't think that should be viewed as a
> primary goal.
>
>> user=`whoami`
>> sems=`ipcs -s|grep $user| awk '{print $2}'`
>> shmem=`ipcs -m|grep $user| awk '{print $2}'`
>
> Consider:
> sems=$(ipcs -s | awk '$5 == "'"$user"'" { print $2 }'`
>
> I may have the quoting wrong,
If you have doubts about correct quoting consider to pass the argument
through an awk variable, which is IMO also a much clearer and cleaner
construct.
sems=$( ipcs -s | awk -v user="$user" '$5 == user { print $2 }' )
Janis
> but the intent is to have awk do the
> check directly. Consider what happens, otherwise, if you have a user
> named 'heel' and a semaphore owned by group 'wheel'.
>
[snip]
Seebs
> If you have doubts about correct quoting consider to pass the argument
> through an awk variable, which is IMO also a much clearer and cleaner
> construct.
D'oh! Right you are.
> sems=$( ipcs -s | awk -v user="$user" '$5 == user { print $2 }' )
That is much prettier.
marty....@gmail.com
> On 2011-01-08, Janis Papanagnou <janis_papanag...@hotmail.com> wrote:
>
> > If you have doubts about correct quoting consider to pass the argument
> > through an awk variable, which is IMO also a much clearer and cleaner
> > construct.
>
> D'oh! Right you are.
>
> > sems=$( ipcs -s | awk -v user="$user" '$5 == user { print $2 }' )
>
> That is much prettier.
>
> -s
> --
> I am not speaking for my employer, although they do rent some of my opinions.
eschew variables: use bash functions. (debugging left to the
interested parties)
# new -- 5 lines
uipcs() { ipcs -$1 | grep $2 | awk '{ print $2 }'; }
foreachi() { cmd=$1; g=$2; shift 2; for a; do $cmd $g $a; done;
echo $# for user $g removed; }
myipcrm() { ipcrm -$1 $2; }
wholelot() { foreachi myipcrm s $(uipcs s $1); foreachi myipcrm m
$(uipcs m $1); }
wholelot $(whoami)
# old -- 18 lines
user=`whoami`
sems=`ipcs -s|grep $user| awk '{print $2}'`
shmem=`ipcs -m|grep $user| awk '{print $2}'`
count=0
for semaphore in $sems
do
ipcrm -s $semaphore
((count=count+1))
done
echo "$count semaphores for $user removed"