2-Cent Tips

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From: Allan Peda <[email protected]>
To: [email protected]

Subject: Two Cent tip

#!/bin/bash
#
# Allan Peda
# April 17, 2009
#
# function to call a long running script with a
# user set timeout period
# Script must have the executable bit set
#
 
# Note that "at" rounds down to the nearest minute
# best to use use full path
function timeout {
   if [[ ${1//[^[:digit:]]} != ${1} ]]; then
      echo "First argument of this function is timeout in minutes." >&2
      return 1
   fi
   declare -i timeout_minutes=${1:-1}
   shift
   # sanity check, can this be run at all?
   if [ ! -x $1 ]; then
      echo "Error: attempt to locate background executable failed." >&2
      return 2
   fi
   "$@" &
   declare -i bckrnd_pid=$!
   declare -i jobspec=$(echo kill -9 $bckrnd_pid |\
                        at now + $timeout_minutes minutes 2>&1 |\
                        perl -ne 's/\D+(\d+)\b.+/$1/ and print')
   # echo kill -9 $bckrnd_pid | at now + $timeout_minutes minutes
   # echo "will kill -9 $bckrnd_pid after $timeout_minutes minutes" >&2
   wait $bckrnd_pid
   declare -i rc=$?
   # cleanup unused batch job
   atrm $jobspec
   return $rc
}
 
# test case:
# ask child to sleep for 163 seconds
# putting process into the background, the reattaching
# but kill it after 2 minutes, unless it returns
# before then
 
# timeout 2 /bin/sleep 163
# echo "returned $? after $SECONDS seconds."

Date: Wed, 20 May 2009 14:43:43 +0000 (GMT)
From: Paul Sands <[email protected]>
Subject: 2-cent Tip - Poor Man's Computer Books
To: [email protected]

-- 
* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

$ cat /proc/<pid of your process>/smaps | grep Swap

$ cat /proc/<pid of your process>/smaps | grep Swap | awk '{ SUM +=
$2 } END { print SUM }'

#!/bin/sh
# Retrieve a list for fragmented files, #fragments:filename
flist() {
  for i in *; do
    if [ -f $i ]; then
      ff=`filefrag $i`
      fn=`echo $ff | cut -f1 -d':'`
      fs=`echo $ff | cut -f2 -d':' | cut -f2 -d' '`
      if [ -f $fn -a $fs -gt 1 ]; then echo -e "$fs:$fn"; fi
    fi
  done
}
 
# Sort the list numeric, descending
flist | sort -n -r |
(
# for each file
  while read line; do
    fs=`echo $line | cut -f 1 -d':'`
    fn=`echo $line | cut -f 2 -d':'`
# copy the file up to 10 times, preserving permissions
    j=0;
    while [ -f $fn -a $j -lt 10 ]; do
      j=$[ $j + 1 ]
 
      TMP=$$.tmp.$j
      if ! cp -p "$fn" "$TMP"; then
        echo copy failed [$fn]
        j=10
      else
# test the new temp file's fragmentation, and if less than the
# original, move the temp file over the original
        ns=`filefrag $TMP | cut -f2 -d':' | cut -f2 -d' '`
        if [ $ns -lt $fs ]; then
          mv "$TMP" "$fn"
          fs=$ns
          if [ $ns -lt 2 ]; then j=10; fi
        fi
      fi
    done
    j=0;
# clean up temporary files
    while [ $j -lt 10 ]; do
      j=$[ $j + 1 ]
 
      TMP=$$.tmp.$j
      if [ -f $TMP ]; then
        rm $TMP
      else
        j=10
      fi
    done
  done
)
# report fragmentation
for i in *; do if [ -f $i ]; then filefrag $i; fi; done

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The Free International Online Linux Monthly	ISSN: 1934-371X	Main site: http://linuxgazette.net

2-Cent Tips

2-cent Tip: Wrapping a script in a timeout shell

2-cent Tip - Poor Man's Computer Books

2-cent Tip: Checking the amount of swapped out memory owned by a process

2-cent Tip: ext2 fragmentation