Chapter 12 End-User Task As Shell Scripts

1.1 Starting Simple by Printing Dashes

[[email protected] Day0801]$ cat dash.sh
#!/usr/bin/env bash
# cookbook filename: dash
# dash - print a line of dashes
# options: # how many (default 72)
#          -c X use char X instead of dashes
#
#
function usagexit()
{
    printf "usage: %s [-c X] [#]\n" $(basename $0)
    exit 2
} >&2

LEN=72
CHAR='-'
while (( $# > 0 ))
do
   case $1 in
   [0-9]*) LEN=$1;;
   -c) shift
       CHAR=$1;;
    *) usagexit;;
    esac
    shift
done

if (( LEN > 4096 ))
then
    echo "too large" >&2
    exit 3
fi
# build the string to the exact length
DASHES=""
for ((i=0;i<LEN;i++))
do
    DASHES="${DASHES}${CHAR}"
done
printf "%s\n" "$DASHES"
[[email protected] Day0801]$

1.3 Loading Your MP3 Player

Use a shell script to keep track of the available space as it copies files onto the MP3 player, quitting when it is full.

[[email protected] Day0801]$ cat load_mp3.sh
#!/usr/bin/env bash
# cookbook filename: load_mp3
# Fill up my mp3 player with as many songs as will fit.
# N.B.: This assumes that the mp3 player is mounted on /media/mp3
#

# determine the size of a file
#
function FILESIZE ()
{
   FN=${1:-/dev/null}
   if [[ -e $FN ]]
   then
      # FZ=$(ls -s $FN | cut -d ' ' -f 1)
           set -- $(ls -s "$FN")
           FZ=$1
   fi
}

#
# compute the freespace on the mp3 player
#
function FREESPACE
{
    # FREE=$(df /media/mp3 | awk '/^/dev/ {print $4}')
    set -- $(df /media/mp3 | grep '^/dev/')
    FREE=$4
}

# substract the (given) filesize from the (global) freespace
function REDUCE()
(( FREE-=${1:-0}))

#
# main:
#
let SUM=0
let COUNT=0
export FZ
export FREE
FREESPACE
find . -name '*.mp3' -print | \
(while read PATHNM
do
  FILESIZE "$PATHNM"
  if ((FZ <= FREE))
  then
      echo loading $PATHNM
      cp "$PATHNM" /media/mp3
      if (( $? == 0 ))
      then
          let SUM+=FZ
          let COUNT++
          REDUCE $FZ
      else
          echo "bad copy of $PATHNM to /media/mp3"
          rm -f /media/mp3/$(basename "$PATHNM")
          # recompute because we don't know how far it got
          FREESPACE
     fi
     # any reason to go on?
     if (( FREE <= 0 ))
     then
         break
     fi
 else
     echo skipping $PATHNM
 fi
done
printf "loaded %d songs (%d blocks)" $COUNT $SUM
printf " onto /media/mp3 (%d blocks free)\n" $FREE
)
# end of script
[[email protected] Day0801]$ 

 1.5 Comparing Two Documents

First, use an office suite that will let you save your documents in Open Document Format (ODF). This is the case for packages like OpenOffice.org while other commercial packages have promised to add support soon. Once you have your files in ODF, you can use a shell script to compare just the content of the files. We stress the word content here because the formatting differences are another issue, and it is (usually) the content that is the most important determinant of which version is new or more important to the end user.

[[email protected] Day0801]$ cat oodiff.sh
#!/usr/bin/env bash
# cookbook filename: oodiff
# oodiff -- diff the CONTENTS of two OpenOffice.org files
# works only on .odt files
#
function usagexit ( )
{
        echo "usage: $0 file1 file2"
        echo "where both files must be .odt files"
        exit $1
} >&2

# assure two readable arg filenames which end in .odt
if (( $# != 2 ))
then
        usagexit 1
fi
if [[ $1 != *.odt || $2 != *.odt ]]
then
        usagexit 2
fi
if [[ ! -r $1 || ! -r $2 ]]
then
        usagexit 3
fi

BAS1=$(basename "$1" .odt)
BAS2=$(basename "$2" .odt)

# unzip them someplace private
PRIV1="/tmp/${BAS1}.$$_1"
PRIV2="/tmp/${BAS2}.$$_2"

# make absolute
HERE=$(pwd)
if [[ ${1:0:1} == '/' ]]
then
        FULL1="${1}"
else
        FULL1="${HERE}/${1}"
fi

# make absolute
if [[ ${2:0:1} == '/' ]]
then
        FULL2="${2}"
else
        FULL2="${HERE}/${2}"
fi

# mkdir scratch areas and check for failure
# N.B. must have whitespace around the { and } and
# must have the trailing ; in the {} lists
mkdir "$PRIV1" || { echo Unable to mkdir $PRIV1 ; exit 4; }
mkdir "$PRIV2" || { echo Unable to mkdir $PRIV2 ; exit 5; }

cd "$PRIV1"
unzip -q "$FULL1"
sed -e 's/>/>\
        /g' -e 's/</\
        </g' content.xml > contentwnl.xml

cd "$PRIV2"
unzip -q "$FULL2"
sed -e 's/>/>\
        /g' -e 's/</\
        </g' content.xml > contentwnl.xml

cd $HERE

diff "${PRIV1}/contentwnl.xml" "${PRIV2}/contentwnl.xml"

rm -rf $PRIV1 $PRIV2
[[email protected] Day0801]$