Very Computer

I've got a question about ksh and the use of quoting in a $( .. ) block:

hithere="just testing"

select foo
from bar
where baz='${hithere}';
exit;
EOF ) || exit 1

What happens in this case is that sqlplus complains because it
sees double quotes in its input, instead of single quotes. If I replace
the $( ... ) with backticks ` it works fine.

Am I doing Something Ugly(tm) here? I prefer to use a $( ... ) block,
but how can I get the quoting right?

Thanks,
--
Jurjen Oskam

PGP Key available at http://www.stupendous.org/

Compare what occurs when I feed these different shell segments to ksh
(at least the version I have handy).  If I use bash, I also get similar
results if there's no space between the EOF and closing ) or ` (and with
a space in there, results are slightly different, but also other than
what the code would imply was intended).

ksh input:
hithere="just testing"
output=$(cat <<EOF
baz='${hithere}';
EOF )
echo "$? $output"

ksh output (including stderr):
ksh: here document `EOF' unclosed

ksh input:
hithere="just testing"
output=$(cat <<EOF
baz='${hithere}';
EOF)
echo "$? $output"

ksh output (including stderr):
0 baz='just testing';

ksh input:
hithere="just testing"
output=`cat <<EOF
baz='${hithere}';
EOF `
echo "$? $output"

ksh output (including stderr):
ksh: here document `EOF' unclosed

ksh input:
hithere="just testing"
output=`cat <<EOF
baz='${hithere}';
EOF`
echo "$? $output"

ksh output (including stderr):
0 baz='just testing';

Note also that within here document, only command substitution,
parameter substitution and backslash quoting is done - all else is
passed literally.  (These substitutions are suppressed if any part of
marker is quoted, and if <<- is used instead of <<, leading tabs are
stripped).

So, if you have shell script including:

hithere="just testing"

select foo
from bar
where baz='${hithere}';
exit;
EOF ) || exit 1

ignore precisely how and where your here document is terminated or if
it's missing termination) is:
select foo
from bar
where baz='just testing';
exit;

e.g. just testing gets substituted in place of ${hithere} and the rest

|       << marker
|              after reading the command line containing this kind
|              of redirection (called a here document), the  shell
|              copies  lines from the command source into a tempo-
|              rary file until a line  matching  marker  is  read.
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...

ksh(1)
Caveat: your ksh mileage may vary.

Quote:> ksh input:
> hithere="just testing"
> output=$(cat <<EOF
> baz='${hithere}';
> EOF)
> echo "$? $output"

> ksh output (including stderr):
> 0 baz='just testing';

#!/bin/ksh
USER="joskam"
output=`cat << EOF
baz='${USER}';
EOF`
print -- "${?}:${output}"

...produces the following output:

0:baz='joskam';

If I change the script to:

#!/bin/ksh
USER="joskam"
output=$(cat << EOF
baz='${USER}';
EOF)
print -- "${?}:${output}"

... the output changes to:

0:baz="${USER}";

Which is obviously not what you're seeing.

Quote:> Caveat: your ksh mileage may vary.

AIX 5.2 also comes with ksh93 (Version M-12/28/93e). Given the following
script, named try3.sh:

#!/bin/false
USER="joskam"
output=$(cat << EOF
baz='${USER}';
EOF)
print -- "${?}:${output}"

... gives the following results:

$ echo ${.sh.version}
Version M-12/28/93e
$ . ./try3.sh
ksh93: .: syntax error: `(' unmatched.

$ exit

$ temp/ksh93       /* the "real" ksh93 binary downloaded from kornshell.com */
$ echo ${.sh.version}
Version M 1993-12-28 o+
$ . ./try3.sh
0:
$

The following script, named try4.sh:

#!/bin/false
USER="joskam"
output=`cat << EOF
baz='${USER}';
EOF`
print -- "${?}:${output}"

... gives the following results:

$ echo ${.sh.version}
Version M-12/28/93e
$ . ./try4.sh
0:
$ exit

$ temp/ksh93
$ echo ${.sh.version}
Version M 1993-12-28 o+
$ . ./try4.sh
0:
$

I don't know why in ksh93 it doesn't seem to work at all...

--
Jurjen Oskam

PGP Key available at http://www.stupendous.org/