examples/scripts/dd-ex.sh

   1 #!/bin/sh
   2
   3 # this is a line editor using only /bin/sh, /bin/dd and /bin/rm
   4
   5 # /bin/rm is not really required, but it is nice to clean up temporary files
   6
   7 PATH=
   8 dd=/bin/dd
   9 rm=/bin/rm
  10
  11 # temporary files we might need
  12 tmp=/tmp/silly.$$
  13 ed=/tmp/ed.$$
  14 trap "$rm -f $tmp $tmp.1 $tmp.2 $tmp.3 $tmp.4 $tmp.5 $tmp.6 $ed.a $ed.b $ed.c; exit" 0 1 2 3
  15
  16 # from now on, no more rm - the above trap is enough
  17 unset rm
  18
  19 # we do interesting things with IFS, but better save it...
  20 saveIFS="$IFS"
  21
  22 # in case "echo" is not a shell builtin...
  23
  24 Echo () {
  25 case "$1" in
  26   -n) shift
  27       $dd of=$tmp 2>/dev/null <<EOF
  28 $@
  29 EOF
  30       IFS="+"
  31       set `$dd if=$tmp bs=1 of=/dev/null skip=1 2>&1`
  32       IFS="$saveIFS"
  33       $dd if=$tmp bs=1 count=$1 2>/dev/null
  34       ;;
  35   *)  $dd 2>/dev/null <<EOF
  36 $@
  37 EOF
  38       ;;
  39 esac
  40 }
  41
  42 # this is used to generate garbage files
  43
  44 true () {
  45   return 0
  46 }
  47
  48 false () {
  49   return 1
  50 }
  51
  52 zero () {
  53   ( trap 'go=false' 13
  54     go=true
  55     while $go
  56     do
  57       $dd "if=$0"
  58       case "$?" in
  59         0) ;;
  60         *) go=false ;;
  61       esac
  62     done
  63   ) 2>/dev/null
  64 }
  65
  66 # arithmetic using dd!
  67
  68 # add variable n1 n2 n3...
  69 # assigns n1+n2+n3+... to variable
  70
  71 add () {
  72   result="$1"
  73   shift
  74   $dd if=/dev/null of=$tmp bs=1 2>/dev/null
  75   for n in "$@"
  76   do
  77     case "$n" in
  78       0) ;;
  79       *) zero | $dd of=$tmp.1 bs=1 "count=$n" 2>/dev/null
  80          ( $dd if=$tmp; $dd if=$tmp.1 ) 2>/dev/null | $dd of=$tmp.2 2>/dev/null
  81          $dd if=$tmp.2 of=$tmp 2>/dev/null
  82          ;;
  83     esac
  84   done
  85   IFS="+"
  86   set `$dd if=$tmp bs=1 of=/dev/null 2>&1`
  87   IFS="$saveIFS"
  88   eval $result='$1'
  89 }
  90
  91 # subtract variable n1 n2
  92 # subtracts n2 from n1, assigns result to variable
  93
  94 subtract () {
  95   result="$1"
  96   zero | $dd of=$tmp bs=1 "count=$2" 2>/dev/null
  97   IFS="+"
  98   set `$dd if=$tmp bs=1 of=/dev/null "skip=$3" 2>&1`
  99   IFS="$saveIFS"
 100   case "$1" in
 101     dd*) set 0 ;;
 102   esac
 103   eval $result='$1'
 104 }
 105
 106 # multiply variable n1 n2
 107 # variable = n1 * n2
 108
 109 multiply () {
 110   result="$1"
 111   zero | $dd "bs=$2" of=$tmp "count=$3" 2>/dev/null
 112   IFS="+"
 113   set `$dd if=$tmp bs=1 of=/dev/null 2>&1`
 114   IFS="$saveIFS"
 115   eval $result='$1'
 116 }
 117
 118 # divide variable n1 n2
 119 # variable = int( n1 / n2 )
 120
 121 divide () {
 122   result="$1"
 123   zero | $dd bs=1 of=$tmp "count=$2" 2>/dev/null
 124   IFS="+"
 125   set `$dd if=$tmp "bs=$3" of=/dev/null 2>&1`
 126   IFS="$saveIFS"
 127   eval $result='$1'
 128 }
 129
 130 # compare variable n1 n2 sets variable to lt if n1<n2, gt if n1>n2, eq if n1==n2
 131
 132 compare () {
 133   res="$1"
 134   n1="$2"
 135   n2="$3"
 136   subtract somename "$n1" "$n2"
 137   case "$somename" in
 138     0) ;;
 139     *) eval $res=gt; return;
 140   esac
 141   subtract somename "$n2" "$n1"
 142   case "$somename" in
 143     0) ;;
 144     *) eval $res=lt; return;
 145   esac
 146   eval $res=eq
 147 }
 148
 149 # lt n1 n2 returns true if n1 < n2
 150
 151 lt () {
 152   n1="$1"
 153   n2="$2"
 154   subtract somename "$n2" "$n1"
 155   case "$somename" in
 156     0) return 1 ;;
 157   esac
 158   return 0
 159 }
 160
 161 # le n1 n2 returns true if n1 <= n2
 162
 163 le () {
 164   n1="$1"
 165   n2="$2"
 166   subtract somename "$n1" "$n2"
 167   case "$somename" in
 168     0) return 0 ;;
 169   esac
 170   return 1
 171 }
 172
 173 # gt n1 n2 returns true if n1 > n2
 174
 175 gt () {
 176   n1="$1"
 177   n2="$2"
 178   subtract somename "$n1" "$n2"
 179   case "$somename" in
 180     0) return 1 ;;
 181   esac
 182   return 0
 183 }
 184
 185 # ge n1 n2 returns true if n1 >= n2
 186
 187 ge () {
 188   n1="$1"
 189   n2="$2"
 190   subtract somename "$n2" "$n1"
 191   case "$somename" in
 192     0) return 0 ;;
 193   esac
 194   return 1
 195 }
 196
 197 # useful functions for the line editor
 198
 199 # open a file - copy it to the buffers
 200
 201 open () {
 202   file="$1"
 203   set `$dd "if=$file" of=/dev/null 2>&1`
 204   case "$1" in
 205     dd*) return 1
 206   esac
 207   # copy the first line to $ed.c
 208   go=true
 209   len=0
 210   while $go
 211   do
 212     case "`$dd "if=$file" bs=1 skip=$len count=1 2>/dev/null`" in
 213       ?*) go=true ;;
 214       *) go=false ;;
 215     esac
 216     add len 1 $len
 217   done
 218   # now $len is the length of the first line (including newline)
 219   $dd "if=$file" bs=1 count=$len of=$ed.c 2>/dev/null
 220   $dd "if=$file" bs=1 skip=$len of=$ed.b 2>/dev/null
 221   $dd if=/dev/null of=$ed.a 2>/dev/null
 222   lineno=1
 223 }
 224
 225 # save a file - copy the buffers to the file
 226
 227 save () {
 228   # make a backup copy of the original
 229   $dd "if=$1" "of=$1.bak" 2>/dev/null
 230   # and save
 231   ( $dd if=$ed.a; $dd if=$ed.c; $dd if=$ed.b ) > "$1" 2>/dev/null
 232 }
 233
 234 # replace n1 n2 bla replaces n2 chars of current line, starting n1-th
 235
 236 replace () {
 237   $dd if=$ed.c of=$tmp.1 bs=1 "count=$1" 2>/dev/null
 238   ( $dd if=$ed.c "skip=$1" bs=1 | $dd of=$tmp.2 bs=1 "skip=$2" ) 2>/dev/null
 239   shift
 240   shift
 241   ( $dd if=$tmp.1; Echo -n "$@"; $dd if=$tmp.2 ) > $tmp.3 2>/dev/null
 242   $dd if=$tmp.3 of=$ed.c 2>/dev/null
 243 }
 244
 245 # rstring n s bla
 246 # replace the n-th occurence of s with bla
 247
 248 rstring () {
 249   n="$1"
 250   shift;
 251   # first we have to find it - this is fun!
 252   # we have $tmp.4 => text before string, $tmp.5 => text after
 253   $dd if=/dev/null of=$tmp.4 2>/dev/null
 254   $dd if=$ed.c of=$tmp.5 2>/dev/null
 255   string="$1"
 256   shift
 257   $dd of=$tmp.6 2>/dev/null <<EOF
 258 $@
 259 EOF
 260   while :
 261   do
 262     case "`$dd if=$tmp.5 2>/dev/null`" in
 263       $string*)
 264           if lt $n 2
 265           then
 266             # now we want to replace the string
 267             Echo -n "$@" > $tmp.2
 268             Echo -n "$string" > $tmp.1
 269             IFS="+"
 270             set `$dd bs=1 if=$tmp.1 of=/dev/null 2>&1`
 271             IFS="$saveIFS"
 272             slen=$1
 273             IFS="+"
 274             ( $dd if=$tmp.4; $dd if=$tmp.2; $dd if=$tmp.5 bs=1 skip=$slen ) \
 275                   2>/dev/null > $tmp
 276             $dd if=$tmp of=$ed.c 2>/dev/null
 277             return 0
 278           else
 279             subtract n $n 1
 280             ( $dd if=$tmp.4; $dd if=$tmp.5 bs=1 count=1 ) > $tmp 2>/dev/null
 281             $dd if=$tmp of=$tmp.4 2>/dev/null
 282             # and remove it from $tmp.5
 283             $dd if=$tmp.5 of=$tmp bs=1 skip=1 2>/dev/null
 284             $dd if=$tmp of=$tmp.5 2>/dev/null
 285           fi
 286           ;;
 287       ?*) # add one more byte...
 288           ( $dd if=$tmp.4; $dd if=$tmp.5 bs=1 count=1 ) > $tmp 2>/dev/null
 289           $dd if=$tmp of=$tmp.4 2>/dev/null
 290           # and remove it from $tmp.5
 291           $dd if=$tmp.5 of=$tmp bs=1 skip=1 2>/dev/null
 292           $dd if=$tmp of=$tmp.5 2>/dev/null
 293           ;;
 294       *)  # not found
 295           return 1
 296           ;;
 297     esac
 298   done
 299 }
 300
 301 # skip to next line
 302 next () {
 303   add l $lineno 1
 304   ( $dd if=$ed.a; $dd if=$ed.c ) 2>/dev/null > $tmp.3
 305   $dd if=$ed.b of=$tmp.4 2>/dev/null
 306   open $tmp.4
 307   $dd if=$tmp.3 of=$ed.a 2>/dev/null
 308   lineno=$l
 309 }
 310
 311 # delete current line
 312 delete () {
 313   l=$lineno
 314   $dd if=$ed.a 2>/dev/null > $tmp.1
 315   $dd if=$ed.b of=$tmp.2 2>/dev/null
 316   open $tmp.2
 317   $dd if=$tmp.1 of=$ed.a 2>/dev/null
 318   lineno=$l
 319 }
 320
 321 # insert before current line (without changing current)
 322 insert () {
 323   ( $dd if=$ed.a; Echo "$@" ) 2>/dev/null > $tmp.1
 324   $dd if=$tmp.1 of=$ed.a 2>/dev/null
 325   add lineno $lineno 1
 326 }
 327
 328 # previous line
 329 prev () {
 330   case "$lineno" in
 331     1) ;;
 332     *) subtract lineno $lineno 1
 333        # read last line of $ed.a
 334        IFS='+'
 335        set `$dd if=$ed.a of=/dev/null bs=1 2>&1`
 336        IFS="$saveIFS"
 337        size=$1
 338        # empty?
 339        case "$size" in
 340          0) return ;;
 341        esac
 342        subtract size $size 1
 343        # skip final newline
 344        case "$size" in
 345          0) ;;
 346          *) subtract size1 $size 1
 347             case "`$dd if=$ed.a bs=1 skip=$size count=1 2>/dev/null`" in
 348               ?*) ;;
 349               *) size=$size1 ;;
 350             esac
 351             ;;
 352        esac
 353        go=true
 354        while $go
 355        do
 356          case "$size" in
 357            0) go=false ;;
 358            *) case "`$dd if=$ed.a bs=1 skip=$size count=1 2>/dev/null`" in
 359                 ?*)  go=true; subtract size $size 1 ;;
 360                 *)   go=false; add size $size 1 ;;
 361               esac
 362               ;;
 363          esac
 364        done
 365        # now $size is the size of the first n-1 lines
 366        # add $ed.c to $ed.b
 367        ( $dd if=$ed.c; $dd if=$ed.b ) 2>/dev/null > $tmp.5
 368        $dd if=$tmp.5 of=$ed.b 2>/dev/null
 369        # move line to ed.c
 370        case "$size" in
 371          0) $dd if=$ed.a of=$ed.c 2>/dev/null
 372             $dd if=/dev/null of=$tmp.5 2>/dev/null
 373             ;;
 374          *) $dd if=$ed.a of=$ed.c bs=1 skip=$size 2>/dev/null
 375             $dd if=$ed.a of=$tmp.5 bs=1 count=$size 2>/dev/null
 376             ;;
 377        esac
 378        # move rest to ed.a
 379        $dd if=$tmp.5 of=$ed.a 2>/dev/null
 380     ;;
 381   esac
 382 }
 383
 384 # goes to a given line
 385 goto () {
 386   rl="$1"
 387   compare bla "$rl" $lineno
 388   case "$bla" in
 389     eq) return
 390         ;;
 391     gt) while gt "$rl" $lineno
 392         do
 393           next
 394         done
 395         ;;
 396     lt) while lt "$rl" $lineno
 397         do
 398           prev
 399         done
 400         ;;
 401   esac
 402 }
 403
 404 lineout () {
 405   Echo -n "$lineno: "
 406   $dd if=$ed.c 2>/dev/null
 407 }
 408
 409 state=closed
 410 name=
 411 autoprint=true
 412
 413 while true
 414 do
 415   Echo -n '> '
 416   read cmd arg
 417   case "$cmd:$state" in
 418     open:open) Echo "There is a file open already" ;;
 419     open:*) if open "$arg"
 420             then state=open; name="$arg"; $autoprint
 421             else Echo "Cannot open $arg"
 422             fi
 423             ;;
 424     new:open) Echo "There is a file open already" ;;
 425     new:*)  open "$arg"
 426             state=open
 427             name="$arg"
 428             $autoprint
 429             ;;
 430     close:changed) Echo "Use 'discard' or 'save'" ;;
 431     close:closed) Echo "Closed already" ;;
 432     close:*) state=closed ;;
 433     save:closed) Echo "There isn't a file to save" ;;
 434     save:*) case "$arg" in
 435               ?*) save "$arg" ;;
 436               *) save "$name" ;;
 437             esac
 438             state=open
 439             ;;
 440     discard:changed) Echo "Your problem!"; state=closed ;;
 441     discard:*) state=closed ;;
 442     print:closed) Echo "No current file" ;;
 443     print:*) lineout ;;
 444     goto:closed) Echo "No current file" ;;
 445     goto:*) goto "$arg"; $autoprint ;;
 446     next:closed) Echo "No current file" ;;
 447     next:*) next; $autoprint ;;
 448     prev:closed) Echo "No current file" ;;
 449     prev:*) prev; $autoprint ;;
 450     name:closed) Echo "No current file" ;;
 451     name:*) name="$arg" ;;
 452     replace:closed) Echo "No current file" ;;
 453     replace:*) if rstring 1 $arg
 454                then state=changed; $autoprint
 455                else Echo "Not found"
 456                fi
 457                ;;
 458     nreplace:closed) Echo "No current file" ;;
 459     nreplace:*) if rstring $arg
 460                 then state=changed; $autoprint
 461                 else Echo "Not found"
 462                 fi
 463                 ;;
 464     delete:closed) Echo "No current file" ;;
 465     delete:*) delete; state=changed; $autoprint ;;
 466     insert:closed) Echo "No current file" ;;
 467     insert:*) insert "$arg"; prev; state=changed; $autoprint ;;
 468     quit:changed) Echo "Use 'save' or 'discard'" ;;
 469     quit:*) Echo "bye"; exit;;
 470     autoprint:*) autoprint="lineout" ;;
 471     noprint:*) autoprint="" ;;
 472     :*) ;;
 473     *) Echo "Command not understood" ;;
 474   esac
 475 done
 476