Shell Programming and Scripting

#!/bin/sh

p1=$1
p2=$2
SEARCH=`grep $p1 $3 | wc -l`

while [ ! -z "$3" ]
do
  if [ $SEARCH -ge 1 ]
  then
    mv $3 $3.bak
    sed -e "s/$p1/$p2/g" $3.bak > $3
    shift
  else
    shift
  fi
done

for file in $(find . -type f -name "*.txt" -print)
do
		cp $file $file.bak
		sed 's/pattern1/pattern2/g' $file > $file.tmp
		mv $file.tmp $file
done

#!/bin/sh

p1=$1
p2=$2

while [ ! -z "$3" ]
do
  SEARCH=`grep $p1 $3 | wc -l`
  if [ $SEARCH -ge 1 ]
  then
    mv $3 $3.bak
    sed -e "s/$p1/$p2/g" $3.bak > $3
    shift
  else
    shift
  fi
done

  if [ $SEARCH -ge 1 ] ;
  then

# test number of args
[ "$#" -lt 2 ] && exit 1

str="$1"
strnew="$2"
# destroy first args
shift 2

# loop rest args
for infile in $*
do
      # grep return exit <>0 if not true = continue = next file
      grep "$str"  "$infile"  >/dev/null 2>&1 || continue

      # include $str, replace, save original (.bak)
      bak="$infile.bak"
      mv "$infile" "$bak"
      sed "s/$str/$strnew/g" "$bak" > "$infile"
done

if cmd ; then
   some
fi
# or
if cmd 
then
   some
fi