[GRASS-dev] g.mlist as C implementation?

[Glynn Clements]

Hamish wrote:

> Glynn Clements wrote:
> > 
> > Markus Neteler wrote:
> > > when using g.mlist in mapsets with thousands of maps in
> > > it (as happens with MODIS time series), it gets extremely
> > > slow.
> ..
> Glynn Clements wrote:
> > The main thing which stands out is that it invokes "grep" once for
> > every name returned by g.list:
> 
> see attached patch for consideration. Following Glynn's suggestion it
> gets rid of the loop for each map name, making the script ~50% faster
> than before, but still about twice as slow as a single call to g.list.

Here's my proposed alternative. It avoids the use of backticks in
favour of a pipeline ending in a while loop.

-- 
Glynn Clements <glynn at gclements.plus.com>

-------------- next part --------------
--- scripts/g.mlist/g.mlist~	2007-04-19 17:45:00.000000000 +0100
+++ scripts/g.mlist/g.mlist	2007-09-10 19:20:51.000000000 +0100
@@ -56,29 +56,25 @@
 #%end
 
 do_list() {
-    list=""
-    for i in `g.list type=$type mapset=$mapset | grep -v '^-\+$' | grep -v "files available" | grep -vi "mapset"`
-    do
-        if [ ! "$search" ] ; then
-    	list="$list $i"
-        else
-    	list="$list `echo $i | grep \"$search\"`"
-        fi
-    done
-
-    if [ ! "$list" ] ; then
-	return
+    if [ ! "$search" ] ; then
+	search="."
     fi
 
-    sorted_list=`echo "$list" | tr ' ' '\n' | sort | tr '\n' ' '`
-
     if [ $GIS_FLAG_M -eq 1 ] ; then
 	MAPSET="@$mapset"
     else
 	MAPSET=""
     fi
-    i=""
-    for i in $sorted_list
+
+    g.list type=$type mapset=$mapset \
+	| grep -v '^-\+$' \
+	| grep -v "files available" \
+	| grep -vi "mapset" \
+	| sed 's/  */\n/g' \
+	| grep -v '^$' \
+	| grep "$search" \
+	| sort \
+	| while read i
     do
         if [ "$start" ] ; then
 	    if [ -z "$sep" ] ; then