#!/bin/sh# this is a line editor using only /bin/sh, /bin/dd and /bin/rm# /bin/rm is not really required, but it is nice to clean up temporary filesPATH=dd=/bin/ddrm=/bin/rm# temporary files we might needtmp=/tmp/silly.$$ed=/tmp/ed.$$trap "$rm -f $tmp $tmp.1 $tmp.2 $tmp.3 $tmp.4 $tmp.5 $tmp.6 $ed.a $ed.b $ed.c; exit" 0 1 2 3# from now on, no more rm - the above trap is enoughunset rm# we do interesting things with IFS, but better save it...saveIFS="$IFS"# in case "echo" is not a shell builtin...Echo () {case "$1" in  -n) shift      $dd of=$tmp 2>/dev/null <<EOF $@EOF      IFS="+"      set `$dd if=$tmp bs=1 of=/dev/null skip=1 2>&1`      IFS="$saveIFS"      $dd if=$tmp bs=1 count=$1 2>/dev/null      ;;  *)  $dd 2>/dev/null <<EOF $@EOF      ;;esac}# this is used to generate garbage filestrue () {  return 0}false () {  return 1}zero () {  ( trap 'go=false' 13    go=true    while $go    do      $dd "if=$0"      case "$?" in	0) ;;	*) go=false ;;      esac    done  ) 2>/dev/null}# arithmetic using dd!# add variable n1 n2 n3...# assigns n1+n2+n3+... to variableadd () {  result="$1"  shift  $dd if=/dev/null of=$tmp bs=1 2>/dev/null  for n in "$@"  do    case "$n" in      0) ;;      *) zero | $dd of=$tmp.1 bs=1 "count=$n" 2>/dev/null	 ( $dd if=$tmp; $dd if=$tmp.1 ) 2>/dev/null | $dd of=$tmp.2 2>/dev/null	 $dd if=$tmp.2 of=$tmp 2>/dev/null	 ;;    esac  done  IFS="+"  set `$dd if=$tmp bs=1 of=/dev/null 2>&1`  IFS="$saveIFS"  eval $result='$1'}# subtract variable n1 n2# subtracts n2 from n1, assigns result to variablesubtract () {  result="$1"  zero | $dd of=$tmp bs=1 "count=$2" 2>/dev/null  IFS="+"  set `$dd if=$tmp bs=1 of=/dev/null "skip=$3" 2>&1`  IFS="$saveIFS"  case "$1" in    dd*) set 0 ;;  esac  eval $result='$1'}# multiply variable n1 n2# variable = n1 * n2multiply () {  result="$1"  zero | $dd "bs=$2" of=$tmp "count=$3" 2>/dev/null  IFS="+"  set `$dd if=$tmp bs=1 of=/dev/null 2>&1`  IFS="$saveIFS"  eval $result='$1'}# divide variable n1 n2# variable = int( n1 / n2 )divide () {  result="$1"  zero | $dd bs=1 of=$tmp "count=$2" 2>/dev/null  IFS="+"  set `$dd if=$tmp "bs=$3" of=/dev/null 2>&1`  IFS="$saveIFS"  eval $result='$1'}# compare variable n1 n2 sets variable to lt if n1<n2, gt if n1>n2, eq if n1==n2compare () {  res="$1"  n1="$2"  n2="$3"  subtract somename "$n1" "$n2"  case "$somename" in    0) ;;    *) eval $res=gt; return;  esac  subtract somename "$n2" "$n1"  case "$somename" in    0) ;;    *) eval $res=lt; return;  esac  eval $res=eq}# lt n1 n2 returns true if n1 < n2lt () {  n1="$1"  n2="$2"  subtract somename "$n2" "$n1"  case "$somename" in    0) return 1 ;;  esac  return 0}# le n1 n2 returns true if n1 <= n2le () {  n1="$1"  n2="$2"  subtract somename "$n1" "$n2"  case "$somename" in    0) return 0 ;;  esac  return 1}# gt n1 n2 returns true if n1 > n2gt () {  n1="$1"  n2="$2"  subtract somename "$n1" "$n2"  case "$somename" in    0) return 1 ;;  esac  return 0}# ge n1 n2 returns true if n1 >= n2ge () {  n1="$1"  n2="$2"  subtract somename "$n2" "$n1"  case "$somename" in    0) return 0 ;;  esac  return 1}# useful functions for the line editor# open a file - copy it to the buffersopen () {  file="$1"  set `$dd "if=$file" of=/dev/null 2>&1`  case "$1" in    dd*) return 1  esac  # copy the first line to $ed.c  go=true  len=0  while $go  do    case "`$dd "if=$file" bs=1 skip=$len count=1 2>/dev/null`" in      ?*) go=true ;;      *) go=false ;;    esac    add len 1 $len  done  # now $len is the length of the first line (including newline)  $dd "if=$file" bs=1 count=$len of=$ed.c 2>/dev/null  $dd "if=$file" bs=1 skip=$len of=$ed.b 2>/dev/null  $dd if=/dev/null of=$ed.a 2>/dev/null  lineno=1}# save a file - copy the buffers to the filesave () {  # make a backup copy of the original  $dd "if=$1" "of=$1.bak" 2>/dev/null  # and save  ( $dd if=$ed.a; $dd if=$ed.c; $dd if=$ed.b ) > "$1" 2>/dev/null}# replace n1 n2 bla replaces n2 chars of current line, starting n1-threplace () {  $dd if=$ed.c of=$tmp.1 bs=1 "count=$1" 2>/dev/null  ( $dd if=$ed.c "skip=$1" bs=1 | $dd of=$tmp.2 bs=1 "skip=$2" ) 2>/dev/null  shift  shift  ( $dd if=$tmp.1; Echo -n "$@"; $dd if=$tmp.2 ) > $tmp.3 2>/dev/null  $dd if=$tmp.3 of=$ed.c 2>/dev/null}# rstring n s bla# replace the n-th occurence of s with blarstring () {  n="$1"  shift;  # first we have to find it - this is fun!  # we have $tmp.4 => text before string, $tmp.5 => text after  $dd if=/dev/null of=$tmp.4 2>/dev/null  $dd if=$ed.c of=$tmp.5 2>/dev/null  string="$1"  shift  $dd of=$tmp.6 2>/dev/null <<EOF$@EOF  while :  do    case "`$dd if=$tmp.5 2>/dev/null`" in      $string*)	  if lt $n 2	  then	    # now we want to replace the string	    Echo -n "$@" > $tmp.2	    Echo -n "$string" > $tmp.1	    IFS="+"	    set `$dd bs=1 if=$tmp.1 of=/dev/null 2>&1`	    IFS="$saveIFS"	    slen=$1	    IFS="+"	    ( $dd if=$tmp.4; $dd if=$tmp.2; $dd if=$tmp.5 bs=1 skip=$slen ) \		  2>/dev/null > $tmp	    $dd if=$tmp of=$ed.c 2>/dev/null	    return 0	  else	    subtract n $n 1	    ( $dd if=$tmp.4; $dd if=$tmp.5 bs=1 count=1 ) > $tmp 2>/dev/null	    $dd if=$tmp of=$tmp.4 2>/dev/null	    # and remove it from $tmp.5	    $dd if=$tmp.5 of=$tmp bs=1 skip=1 2>/dev/null	    $dd if=$tmp of=$tmp.5 2>/dev/null	  fi	  ;;      ?*) # add one more byte...	  ( $dd if=$tmp.4; $dd if=$tmp.5 bs=1 count=1 ) > $tmp 2>/dev/null	  $dd if=$tmp of=$tmp.4 2>/dev/null	  # and remove it from $tmp.5	  $dd if=$tmp.5 of=$tmp bs=1 skip=1 2>/dev/null	  $dd if=$tmp of=$tmp.5 2>/dev/null	  ;;      *)  # not found	  return 1	  ;;    esac  done}# skip to next linenext () {  add l $lineno 1  ( $dd if=$ed.a; $dd if=$ed.c ) 2>/dev/null > $tmp.3  $dd if=$ed.b of=$tmp.4 2>/dev/null  open $tmp.4  $dd if=$tmp.3 of=$ed.a 2>/dev/null  lineno=$l}# delete current linedelete () {  l=$lineno  $dd if=$ed.a 2>/dev/null > $tmp.1  $dd if=$ed.b of=$tmp.2 2>/dev/null  open $tmp.2  $dd if=$tmp.1 of=$ed.a 2>/dev/null  lineno=$l}# insert before current line (without changing current)insert () {  ( $dd if=$ed.a; Echo "$@" ) 2>/dev/null > $tmp.1  $dd if=$tmp.1 of=$ed.a 2>/dev/null  add lineno $lineno 1}# previous lineprev () {  case "$lineno" in    1) ;;    *) subtract lineno $lineno 1       # read last line of $ed.a       IFS='+'       set `$dd if=$ed.a of=/dev/null bs=1 2>&1`       IFS="$saveIFS"       size=$1       # empty?       case "$size" in	 0) return ;;       esac       subtract size $size 1       # skip final newline       case "$size" in	 0) ;;	 *) subtract size1 $size 1	    case "`$dd if=$ed.a bs=1 skip=$size count=1 2>/dev/null`" in	      ?*) ;;	      *) size=$size1 ;;	    esac	    ;;       esac       go=true       while $go       do	 case "$size" in	   0) go=false ;;	   *) case "`$dd if=$ed.a bs=1 skip=$size count=1 2>/dev/null`" in	        ?*)  go=true; subtract size $size 1 ;;	        *)   go=false; add size $size 1 ;;	      esac	      ;;	 esac       done       # now $size is the size of the first n-1 lines       # add $ed.c to $ed.b       ( $dd if=$ed.c; $dd if=$ed.b ) 2>/dev/null > $tmp.5       $dd if=$tmp.5 of=$ed.b 2>/dev/null       # move line to ed.c       case "$size" in	 0) $dd if=$ed.a of=$ed.c 2>/dev/null	    $dd if=/dev/null of=$tmp.5 2>/dev/null	    ;;	 *) $dd if=$ed.a of=$ed.c bs=1 skip=$size 2>/dev/null	    $dd if=$ed.a of=$tmp.5 bs=1 count=$size 2>/dev/null	    ;;       esac       # move rest to ed.a       $dd if=$tmp.5 of=$ed.a 2>/dev/null    ;;  esac}# goes to a given linegoto () {  rl="$1"  compare bla "$rl" $lineno  case "$bla" in    eq) return	;;    gt) while gt "$rl" $lineno	do	  next	done	;;    lt) while lt "$rl" $lineno	do	  prev	done	;;  esac}lineout () {  Echo -n "$lineno: "  $dd if=$ed.c 2>/dev/null}state=closedname=autoprint=truewhile truedo  Echo -n '> '  read cmd arg  case "$cmd:$state" in    open:open) Echo "There is a file open already" ;;    open:*) if open "$arg"	    then state=open; name="$arg"; $autoprint	    else Echo "Cannot open $arg"	    fi	    ;;    new:open) Echo "There is a file open already" ;;    new:*)  open "$arg"	    state=open	    name="$arg"	    $autoprint	    ;;    close:changed) Echo "Use 'discard' or 'save'" ;;    close:closed) Echo "Closed already" ;;    close:*) state=closed ;;    save:closed) Echo "There isn't a file to save" ;;    save:*) case "$arg" in	      ?*) save "$arg" ;;	      *) save "$name" ;;	    esac	    state=open	    ;;    discard:changed) Echo "Your problem!"; state=closed ;;    discard:*) state=closed ;;    print:closed) Echo "No current file" ;;    print:*) lineout ;;    goto:closed) Echo "No current file" ;;    goto:*) goto "$arg"; $autoprint ;;    next:closed) Echo "No current file" ;;    next:*) next; $autoprint ;;    prev:closed) Echo "No current file" ;;    prev:*) prev; $autoprint ;;    name:closed) Echo "No current file" ;;    name:*) name="$arg" ;;    replace:closed) Echo "No current file" ;;    replace:*) if rstring 1 $arg	       then state=changed; $autoprint	       else Echo "Not found"	       fi	       ;;    nreplace:closed) Echo "No current file" ;;    nreplace:*) if rstring $arg		then state=changed; $autoprint		else Echo "Not found"		fi		;;    delete:closed) Echo "No current file" ;;    delete:*) delete; state=changed; $autoprint ;;    insert:closed) Echo "No current file" ;;    insert:*) insert "$arg"; prev; state=changed; $autoprint ;;    quit:changed) Echo "Use 'save' or 'discard'" ;;    quit:*) Echo "bye"; exit;;    autoprint:*) autoprint="lineout" ;;    noprint:*) autoprint="" ;;    :*) ;;    *) Echo "Command not understood" ;;  esacdone