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

["有澤 健治" <karisawa@gmail.com>]

Hello,

Experiment in my server is

hebe% a=`{seq 1 4000}
hebe% echo $a
1 2 3 4 [snip] 3997 3998 3999 4000
hebe%

hebe% ls -l /sys/src/cmd/rc/io.c
--rw-rw-r-- M 98029 sys sys 3757 Oct  5  2019 /sys/src/cmd/rc/io.c
hebe%

Kenji Arisawa

On 2022/01/01 19:26, Michael Forney wrote:
> ---
> This patch requires the other g patch I sent earlier to apply cleanly.
>
> I noticed that with the recent rc changes, I see the message 'Write
> error' on stderr when using g in a large directory (such as
> /sys/src/cmd).  This is because rc now uses io.c code to write env
> files before executing a child, and this fails when the size of a list
> exceeds Maxenvsize.  Previously, these write errors were just ignored.
>
> It can be reproduced with
>
> 	% a=`{seq 1 4000}
> 	% echo
> 	Write error
> 	
> 	%
>
> 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.
>
> 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"`)?
>
> diff 525c7bc4922fc86ba0bbe2281fbe92e697a4f6d8 dd997a744e5ec3704d48dedc259d06c062d56aec
> --- a/rc/bin/g	Sat Jan  1 14:51:39 2022
> +++ b/rc/bin/g	Sat Jan  1 02:26:14 2022
> @@ -14,25 +14,24 @@
>   }
>   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]
> -	exit usage
> -case 1
> -	pattern=$1
> -	files=`$nl{walk -f $recurse | grep -e $fullnames -e $suffixes >[2]/dev/null}
> +	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 -- $f \
> -				| 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 $f
>   	}
> -}
> -grep -n $flags -- $pattern $files /dev/null
> +} | xargs grep -n $flags -- $pattern