Mini Shell

#!/usr/bin/sh

# Bzgrep wrapped for bzip2, 
# adapted from zgrep by Philippe Troin <phil@fifi.org> for Debian GNU/Linux.
## zgrep notice:
## zgrep -- a wrapper around a grep program that decompresses files as needed
## Adapted from a version sent by Charles Levert <charles@comm.polymtl.ca>

PATH="/usr/bin:$PATH"; export PATH

prog=`echo $0 | sed 's|.*/||'`
case "$prog" in
	*egrep)	grep=${EGREP-egrep}	;;
	*fgrep)	grep=${FGREP-fgrep}	;;
	*)	grep=${GREP-grep}	;;
esac
pat=""
while test $# -ne 0; do
  case "$1" in
  -e | -f) opt="$opt $1"; shift; pat="$1"
           if test "$grep" = grep; then  # grep is buggy with -e on SVR4
             grep=egrep
           fi;;
  -A | -B) opt="$opt $1 $2"; shift;;
  -*)	   opt="$opt $1";;
   *)      if test -z "$pat"; then
	     pat="$1"
	   else
	     break;
           fi;;
  esac
  shift
done

if test -z "$pat"; then
  echo "grep through bzip2 files"
  echo "usage: $prog [grep_options] pattern [files]"
  exit 1
fi

list=0
silent=0
op=`echo "$opt" | sed -e 's/ //g' -e 's/-//g'`
case "$op" in
  *l*) list=1
esac
case "$op" in
  *h*) silent=1
esac

if test $# -eq 0; then
  bzip2 -cdfq | $grep $opt "$pat"
  exit $?
fi

res=0
for i do
  if test -f "$i"; then :; else if test -f "$i.bz2"; then i="$i.bz2"; fi; fi
  if test $list -eq 1; then
    bzip2 -cdfq "$i" | $grep $opt "$pat" 2>&1 > /dev/null && echo $i
    r=$?
  elif test $# -eq 1 -o $silent -eq 1; then
    bzip2 -cdfq "$i" | $grep $opt "$pat"
    r=$?
  else
    j=$(echo "$i" | sed 's/\\/&&/g;s/|/\\&/g;s/&/\\&/g')
    j=`printf "%s" "$j" | tr '\n' ' '`
    # A trick adapted from
    # https://groups.google.com/forum/#!original/comp.unix.shell/x1345iu10eg/Nn1n-1r1uU0J
    # that has the same effect as the following bash code:
    # bzip2 -cdfq "$i" | $grep $opt "$pat" | sed "s|^|${j}:|"
    # r=${PIPESTATUS[1]}
    exec 3>&1
    eval `
      exec 4>&1 >&3 3>&-
      {
        bzip2 -cdfq "$i" 4>&-
      } | {
        $grep $opt "$pat" 4>&-; echo "r=$?;" >&4
      } | sed "s|^|${j}:|"
    `
  fi
  test "$r" -ne 0 && res="$r"
done
exit $res