| Title: | DIGITAL UNIX (FORMERLY KNOWN AS DEC OSF/1) |
| Notice: | Welcome to the Digital UNIX Conference |
| Moderator: | SMURF::DENHAM |
| Created: | Thu Mar 16 1995 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 10068 |
| Total number of notes: | 35879 |
Can anyone explain this strange shell behavior? This is on Digital Unix 4.0a. (I admit to being a complete Unix novice, but this is just too weird...) $ cat e.sh cat > dump << EOT This is \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z. This is \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z. This is the \End EOT cat dump $ csh e.sh This is \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z. This is \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z. This is the \End $ ksh e.sh This is \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z. This is \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z. This is the \End $ sh e.sh This is \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z. This is \A\B\C\DE\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z. This is the End What is so special about \E to the Bourne shell??
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 8622.1 | EOF escapee.. work-a-round (if that's what you need) | COMEUP::SIMMONDS | lock (M); while (not *SOMETHING) { Wait(C,M); } unlock(M) | Tue Jan 28 1997 22:37 | 16 |
No explanation, just a workaround for you.. in e.sh, change
cat > dump << EOT
[...]
EOT
to
cat > dump << =EOT=
[...] ^
=EOT= |
^ |
| |
(e.g. some character at this position which is _not_ in
the set that you're Escaping)
John.
| |||||
| 8622.2 | looks like a gray area | NETRIX::"[email protected]" | Farrell Woods | Wed Jan 29 1997 10:29 | 26 |
Usually the backslash is used to "escape" the next character. That is, if the character would normally have some special meaning then the backslash says that the following character should be accepted literally. One might use that feature to embed dollar signs into strings for instance, since normally things that begin with dollar signs are considered to be variable names. Now if you need a literal backslash somewhere you can still escape that with a backslash, as in "\\". The scanner has to look for these (among other things) when considering how to tokenize the shell's input. I'm not sure if there was ever any formal rule that said what to do if the character following the backslash did not have any special meaning in the first place. It would appear that the shells pass the backslash and the following character and do not swallow the backslash. (Try this: instead of using \a\b\c\d etc. in your examples, use \\a\\b\\c etc. I think you'll find that in this case, the Bourne shell will do what you expect.) As .1 points out, the "end of input" token that you defined begins with the letter E. No doubt the Bourne shell's scanner dropped the backslash while trying to see if it had the token "EOT", or something different. -- Farrell [Posted by WWW Notes gateway] | |||||
| 8622.3 | Thanks! | CPEEDY::VATNE | Peter Vatne, PATHWORKS for UNIX Server Engineering | Wed Jan 29 1997 11:18 | 3 |
Thanks for the workaround! It is definitely the interaction between the first letter of the "termination string" and escaped characters in the input stream. We'll incorporate the workaround. | |||||