idx009@cck.cov.ac.uk (the Crisco Kid) (12/05/90)
PROBLEM:
There appears to be an incompatibility in the conversion tables
used to map ASCII <-> EBCDIC in the UNIX dd utility, depending
on whether the UNIX on which dd is used is BSD-derived or SYSV-
derived. This means that a file converted to EBCDIC with a Berkloid
dd is perverted when converted back to ASCII with an AT&T UNIX
dd, and vice-versa (Don't ask me why I wanted to do this!).
EVIDENCE:
A small C program to spit out all characters from octal 0 to octal
377 into a data file. dd conv=ebcdic < data >ebcdic_data on both
machines. od -c < ebcdic_data > map on both machines. diff of the
two map files. Lines flagged '<' are the BSD output, '>' the SYSV
output. In this case, the Berkloid dd is on a Sequent Symmetry,
and the AT&Toid dd is on a Personal Iris.
3c3
< 0000040 @ O 177 { [ l P } M ] \ N k ` K a
---
> 0000040 @ Z 177 { [ l P } M ] \ N k ` K a
6c6
< 0000120 327 330 331 342 343 344 345 346 347 350 351 J 340 Z _ m
---
> 0000120 327 330 331 342 343 344 345 346 347 350 351 255 340 275 232 m
8c8
< 0000160 227 230 231 242 243 244 245 246 247 250 251 300 j 320 241 007
---
> 0000160 227 230 231 242 243 244 245 246 247 250 251 300 O 320 _ 007
13,15c13,15
< 0000300 v w x 200 212 213 214 215 216 217 220 232 233 234 235 236
< 0000320 237 240 252 253 254 255 256 257 260 261 262 263 264 265 266 267
< 0000340 270 271 272 273 274 275 276 277 312 313 314 315 316 317 332 333
---
> 0000300 v w x 200 212 213 214 215 216 217 220 j 233 234 235 236
> 0000320 237 240 252 253 254 J 256 257 260 261 262 263 264 265 266 267
> 0000340 270 271 272 273 274 241 276 277 312 313 314 315 316 317 332 333
SYSTEMS TESTED:
4BSD: GNU dd, Sequent Symmetry
SYSV: IRIX 3.2, UNISOFT 5.1
QUESTION:
Why do SYSV-derived dd and BSD-derived dd differ? Quoting the Sequent
manual page:
The ASCII/EBCDIC conversion tables are taken from the 256
character standard in the CACM Nov, 1968.
Our UNISOFT manual page says the same thing. I don't have the CACM
issue, so I can't tell what's going on here, but somebody is wrong.
What's going on?
Kay
--
There's a hole in my heart where the rain blows through...
Kay Dekker, Dept of Industrial Design, Coventry Poly, Coventry UK
37 Old Winnings Road, Keresley Village, Coventry
Phone: +44 203 838668 (work) +44 203 337865 (home)