threads / patch / 939

patchOptimized print_help()

Subject: [COGITO PATCH] Optimized print_help()

## tl;dr

5 messages between Jun 14, 2005 and Jun 15, 2005. Diffs are folded; open one to read it.

replies: 4people: 3as markdown or json

Pavel Roskin· Jun 14, 2005, 23:26 UTC · lore
Hello!

print_help() in cg-Xlib should not be calling "which" 3 times. It's an external command. The patch caches the result in a local variable.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Show changes to cg-Xlib +4 −3
diff --git a/cg-Xlib b/cg-Xlib
--- a/cg-Xlib
+++ b/cg-Xlib
@@ -130,10 +130,11 @@ update_index () {
 
 
 print_help () {
-	which "cg-$1" >/dev/null 2>&1 || exit 1
-	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $(which cg-$1) 
+	local toolpath=$(which cg-$1 2>/dev/null)
+	[ -z "$toolpath" ] && exit 1
+	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $toolpath
 	echo
-	cat $(which cg-$1) | sed -n '3,/^$/s/^# *//p'
+	cat $toolpath | sed -n '3,/^$/s/^# *//p'
 	exit
 }
 

-- 
Regards,
Pavel Roskin
Jonas Fonseca· Jun 15, 2005, 00:00 UTC · re: Pavel Roskin · lore

Re: [COGITO PATCH] Optimized print_help()

Pavel Roskin <proski@gnu.org> wrote Tue, Jun 14, 2005:
Show 19 quoted lines
> Hello!
> 
> print_help() in cg-Xlib should not be calling "which" 3 times.  It's an
> external command.  The patch caches the result in a local variable.
> 
> Signed-off-by: Pavel Roskin <proski@gnu.org>
> 
> diff --git a/cg-Xlib b/cg-Xlib
> --- a/cg-Xlib
> +++ b/cg-Xlib
> @@ -130,10 +130,11 @@ update_index () {
>  
>  
>  print_help () {
> -	which "cg-$1" >/dev/null 2>&1 || exit 1
> -	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $(which cg-$1) 
> +	local toolpath=$(which cg-$1 2>/dev/null)
> +	[ -z "$toolpath" ] && exit 1
> +	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $toolpath

Shouldn't $toolpath be quoted here to make it safer? Although it seems the make install don't handle irregular toolpaths at the moment.

>  	echo
> -	cat $(which cg-$1) | sed -n '3,/^$/s/^# *//p'
> +	cat $toolpath | sed -n '3,/^$/s/^# *//p'
What about also removing UUOC from this line ...
	sed -n '3,/^$/s/^# *//p' < "$toolpath"
>  	exit
>  }
-- 
Jonas Fonseca
Pavel Roskin· Jun 15, 2005, 00:33 UTC · re: Jonas Fonseca · lore

Re: [COGITO PATCH] Optimized print_help()

On Wed, 2005-06-15 at 02:00 +0200, Jonas Fonseca wrote:
> Shouldn't $toolpath be quoted here to make it safer? Although it seems
> the make install don't handle irregular toolpaths at the moment.
Sure.
> > +	cat $toolpath | sed -n '3,/^$/s/^# *//p'
> 
> What about also removing UUOC from this line ...
UUOC?  I had too look it up :-)

It's not just "useless use of cat", but also useless use of redirection in both cases. I guess sed can exit after it finishes processing the range (I don't know if it actually does), so feeding it the whole file is not need.

OK, here's an improved patch.
Signed-off-by: Pavel Roskin <proski@gnu.org>
Show changes to cg-Xlib +4 −3
diff --git a/cg-Xlib b/cg-Xlib
--- a/cg-Xlib
+++ b/cg-Xlib
@@ -130,10 +130,11 @@ update_index () {
 
 
 print_help () {
-	which "cg-$1" >/dev/null 2>&1 || exit 1
-	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $(which cg-$1) 
+	local toolpath=$(which cg-$1 2>/dev/null)
+	[ -z "$toolpath" ] && exit 1
+	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' "$toolpath"
 	echo
-	cat $(which cg-$1) | sed -n '3,/^$/s/^# *//p'
+	sed -n '3,/^$/s/^# *//p' "$toolpath"
 	exit
 }
 

P.S. Maybe we could use "type" rather than "which" because the former is
a shell built-in.  Or maybe we should hardcode the prefix on install.
Anyway, it's out of scope of this patch.

P.P.S. I hope that $toolpath doesn't start with "-".  I could add "--"
to the sed command line, but I'm not sure if BSD sed would like it.

-- 
Regards,
Pavel Roskin
Rene Scharfe· Jun 15, 2005, 18:58 UTC · re: Pavel Roskin · lore

Re: [COGITO PATCH] Optimized print_help()

Pavel Roskin schrieb:
Show 11 quoted lines
>>> +	cat $toolpath | sed -n '3,/^$/s/^# *//p'
>> 
>> What about also removing UUOC from this line ...
> 
> 
> UUOC?  I had too look it up :-)
> 
> It's not just "useless use of cat", but also useless use of
> redirection in both cases.  I guess sed can exit after it finishes
> processing the range (I don't know if it actually does), so feeding
> it the whole file is not need.

It doesn't matter if the shell opens the file or if sed does it itself, sed's ability to close the file and quit when done doesn't depend on that. So this call is equivalent and has the advantage of being resistant against filenames starting with a "-":

   sed -n '3,/^$/s/^# *//p' <"$toolpath"
Rene
Pavel Roskin· Jun 15, 2005, 21:14 UTC · re: Rene Scharfe · lore

Re: [COGITO PATCH] Optimized print_help()

Hello, Rene!
On Wed, 2005-06-15 at 20:58 +0200, Rene Scharfe wrote:
> It doesn't matter if the shell opens the file or if sed does it itself,
> sed's ability to close the file and quit when done doesn't depend on
> that.
I checked sed 4.1.4 and found following:
1) sed won't close stdin ever, but it will close files specified on the
command line.
2) sed will exit when told to do so by a command such as "q", and it
won't read the reminder of the file, whether it's stdin or not.
3) sed has code that makes it exit after it has processed all address
ranges and the "-n" option is used.  However, this feature is buggy and
disabled by default (see EXPERIMENTAL_DASH_N_OPTIMIZATION). It may be
enabled in the future versions.

In other words, you are correct (except the part about closing the file).

>   So this call is equivalent and has the advantage of being
> resistant against filenames starting with a "-":
> 
>    sed -n '3,/^$/s/^# *//p' <"$toolpath"
OK.  Here's the third version of the patch.
Signed-off-by: Pavel Roskin <proski@gnu.org>
Show changes to cg-Xlib +4 −3
diff --git a/cg-Xlib b/cg-Xlib
--- a/cg-Xlib
+++ b/cg-Xlib
@@ -130,10 +130,11 @@ update_index () {
 
 
 print_help () {
-	which "cg-$1" >/dev/null 2>&1 || exit 1
-	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' < $(which cg-$1) 
+	local toolpath=$(which cg-$1 2>/dev/null)
+	[ -z "$toolpath" ] && exit 1
+	sed -n '/^USAGE=/,0s/.*"\(.*\)"/Usage: \1/p' <"$toolpath"
 	echo
-	cat $(which cg-$1) | sed -n '3,/^$/s/^# *//p'
+	sed -n '3,/^$/s/^# *//p' <"$toolpath"
 	exit
 }
 

-- 
Regards,
Pavel Roskin

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