Ralf Wildenhues wrote:
> Hmm, ok. But traditional shells execute this construct
> while read foo
> do
> $whatever
> done <$file
>
> in a subshell, too, for example Solaris 10 sh.
Ouch. Looking at the variables, it indeed behaves like a subshell.
Looking at the process id, it does not...!
$ cat script.sh
echo $$
echo foo > foo
var="initial value"
while read foo
do
echo foo $$
var="set by code inside while"
done < foo
echo $$
echo "var = $var"
$ /bin/sh script.sh
3908
foo 3908
3908
var = initial value
$ /usr/xpg4/bin/sh script.sh
3910
foo 3910
3910
var = set by code inside while
> To be safe, I think you
> need to `exec <$file', or, restoring stdin, something like this:
> exec 5<&1 <$file
> while read r
> do
> $whatever
> done
> exec <&5 5<&-
Astonishing. I never saw this kind of low-level shell programming.
Applied; see attached patch.
> > Where can I download the shell script profiler that you used?
>
> Hehe. Several crude methods, plus some experience with huge shell
> scripts: Either take a slow terminal emulator and watch `sh -x script'
> fly by, or dump its output, and pipe it through
> sort | uniq -c | sort -k1n
>
> wher both the short tail and any long, similar regions are interesting.
Thanks for all these tips!
> I think it may be possible to shave off another good part, but the next
> changes probably have a higher source code change to improvement ratio
> (caching func_lookup_file results could help; or rewriting func_get_*
> to work on lists of modules; both seem like not too high hanging fruit).
Uhh, I would be a bit reluctant to apply the second type of changes, since
it changes the program structure for no other reason than speed. The major
bottleneck at this time are the autom4te / m4 invocations after gnulib-tool.
(I'm turning off autom4te's caching in my ~/.autom4te.cfg since temporary
directories would be acceptable for me in /tmp, but not in the middle
of my source code directories.)
Caching func_lookup_file results would be acceptable.
Bruno
*** gnulib-tool 18 Sep 2006 13:07:37 -0000 1.165
--- gnulib-tool 18 Sep 2006 15:13:46 -0000
***************
*** 1672,1688 ****
LC_ALL=C join -t"$delimiter" -v2 "$tmp"/old-files "$tmp"/new-files \
| sed -e "$sed_take_last_column" \
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_new_files" >
"$tmp"/added-files
! while read g f; do
! func_add_or_update
! done < "$tmp"/added-files
# Then the files that are in new-files and in old-files:
already_present=true
LC_ALL=C join -t"$delimiter" "$tmp"/old-files "$tmp"/new-files \
| sed -e "$sed_take_last_column" \
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_new_files" >
"$tmp"/kept-files
! while read g f; do
! func_add_or_update
! done < "$tmp"/kept-files
# Command-line invocation printed in a comment in generated gnulib-cache.m4.
actioncmd="gnulib-tool --import"
--- 1672,1698 ----
LC_ALL=C join -t"$delimiter" -v2 "$tmp"/old-files "$tmp"/new-files \
| sed -e "$sed_take_last_column" \
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_new_files" >
"$tmp"/added-files
! { # Rearrange file descriptors. Needed because "while ... done < ..."
! # constructs are executed in a subshell e.g. by Solaris 10 /bin/sh.
! exec 5<&1 < "$tmp"/added-files
! while read g f; do
! func_add_or_update
! done
! exec 1<&5 5<&-
! }
# Then the files that are in new-files and in old-files:
already_present=true
LC_ALL=C join -t"$delimiter" "$tmp"/old-files "$tmp"/new-files \
| sed -e "$sed_take_last_column" \
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_new_files" >
"$tmp"/kept-files
! { # Rearrange file descriptors. Needed because "while ... done < ..."
! # constructs are executed in a subshell e.g. by Solaris 10 /bin/sh.
! exec 5<&1 < "$tmp"/kept-files
! while read g f; do
! func_add_or_update
! done
! exec 1<&5 5<&-
! }
# Command-line invocation printed in a comment in generated gnulib-cache.m4.
actioncmd="gnulib-tool --import"
***************
*** 2069,2087 ****
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_files" \
| LC_ALL=C sort \
> "$tmp"/files
! while read g f; do
! func_lookup_file "$f"
! if test -n "$lookedup_tmp"; then
! cp -p "$lookedup_file" "$testdir/$g"
! else
! ln "$lookedup_file" "$testdir/$g" 2>/dev/null ||
! if test -z "$symbolic"; then
cp -p "$lookedup_file" "$testdir/$g"
else
! ln -s "$lookedup_file" "$testdir/$g"
fi
! fi
! done < "$tmp"/files
# Create $sourcebase/Makefile.am.
mkdir -p "$testdir/$sourcebase"
--- 2079,2102 ----
| sed -e "s,^.*\$,&$delimiter&," -e "$sed_rewrite_files" \
| LC_ALL=C sort \
> "$tmp"/files
! { # Rearrange file descriptors. Needed because "while ... done < ..."
! # constructs are executed in a subshell e.g. by Solaris 10 /bin/sh.
! exec 5<&1 < "$tmp"/files
! while read g f; do
! func_lookup_file "$f"
! if test -n "$lookedup_tmp"; then
cp -p "$lookedup_file" "$testdir/$g"
else
! ln "$lookedup_file" "$testdir/$g" 2>/dev/null ||
! if test -z "$symbolic"; then
! cp -p "$lookedup_file" "$testdir/$g"
! else
! ln -s "$lookedup_file" "$testdir/$g"
! fi
fi
! done
! exec 1<&5 5<&-
! }
# Create $sourcebase/Makefile.am.
mkdir -p "$testdir/$sourcebase"
