Re: [9front] [PATCH] g: use xargs instead of finding complete file list before greping

[igor@9lab.org]

Hi Michael,

Thanks! I have tested your patch and can confirm it works.

Quoth Michael Forney <mforney@mforney.org>:
[…]
> I'm not sure if this error message is desired or not for cases like
> this, but regardless, I think g could be a bit more efficient by using
> xargs rather than enumerating the complete list of files up front,
> avoiding the issue completely.
[…]

xargs also has a parallel mode that comes in handy to speed up search
in this case.

[…]
> One slight issue with this patch is that files named '-n' are skipped.
> I don't think it's too big a deal, but I wasn't quite sure how to
> handle this.  One idea is to use `walk -f -- $f` instead of `echo $f`.
> Another idea is `echo -n $f$nl`.  In general, is there a good way to
> print a variable, regardless of its value (similar to POSIX `printf
> '%s\n' "$f"`)?
[…]

Not sure if there is something similar to POSIX `printf`. I am using
`echo -n $f$nl`.

Below is your patch with minor modifications if anyone else want's to
give this a go and provide further feedback.

Cheers,
Igor

---
diff 31957c1aa36808a2ba4a496fd5a1559ef46b9517 02d9badb3c55e01a8e9d274b89d99f67433f15ec
--- a/rc/bin/g	Tue Jan  4 20:11:07 2022
+++ b/rc/bin/g	Wed Jan  5 00:59:10 2022
@@ -14,25 +14,25 @@
 }
 if(~ $1 --)
 	shift
+if(~ $#* 0) {
+	echo 'usage: g [flags] pattern [files]' >[1=2]
+	exit usage
+}
+pattern=$1
+shift
 
 suffixes='\.([bcChlmsy]|asm|awk|cc|cgi|cpp|cs|go|goc|hs|java|lua|lx|mk|ml|mli|ms|myr|pl|py|rc|sh|tex|xy)$'
 fullnames='(^|/)mkfile$'
 switch($#*){
 case 0
-	echo 'usage: g [flags] pattern [files]' >[1=2]
+	walk -f $recurse | grep -e $fullnames -e $suffixes >[2]/dev/null
 	exit usage
-case 1
-	pattern=$1
-	files=`$nl{walk -f $recurse | grep -e $fullnames -e $suffixes >[2]/dev/null}
 case *
-	pattern=$1
-	shift
 	for(f in $*){
 		if(test -d $f)
-			files=($files `$nl{walk -f $recurse -- $* \
-				| grep -e $fullnames -e $suffixes >[2]/dev/null})
+			walk -f $recurse -- $f \
+				| grep -e $fullnames -e $suffixes >[2]/dev/null
 		if not
-			files=($files $f)
+			echo -n $f$nl
 	}
-}
-grep -n $flags -- $pattern $files /dev/null
+} | xargs -p4 grep -n $flags -- $pattern