hstow: speed up unstowing by using more streaming

1 files changed, 21 insertions, 13 deletions

diff --git a/bin/hstow b/bin/hstow
index 311fce2a..c10b4907 100755
--- a/bin/hstow
+++ b/bin/hstow
@@ -50,6 +50,15 @@ if ! command -v readlink >/dev/null; then
     }
 fi
 
+# Here we unconditionally bypass readlink(1), for speed.
+# The long regexp is because only BREs have backreferences in POSIX.
+readlinks () {
+    while read -r line; do
+	printf '%s\t%s\n' "$line" "$(ls -ld "$line")"
+    done | sed \
+'s/\([^\t]*\)\t\([^[:blank:]]\{1,\}[[:blank:]]\{1,\}\)\{8\}\1 -> /\1\t/'
+}
+
 disjoin_hstow_file () {
     if [ -e "$DIR/$1" ]; then
 	while read -r line; do
@@ -148,19 +157,18 @@ unstow () {
     for file in \
 	$(find . ! \( -user "$(id -un)" -o -group "$(id -gn)" \) \
 	       -prune -o -type l ! -name . ! -name "$cchars" -print \
-	      | grep -Ev "$dirs_pat"); do
-	if readlink "$file" | grep -Eq '^(\.\./)*\.STOW/'"$NAME/"; then
-	    rm "$file"
-	    while true; do
-		file="$(dirname $file)"
-		[ "$file" = . ] && break
-		if [ -z "$(dir_contents $file)" ]; then
-		    rmdir "$file"
-		else
-		    break
-		fi
-	    done
-	fi
+	      | grep -Ev "$dirs_pat" | readlinks | awk -F'\t' \
+		'$2 ~ /^(\.\.\/)*\.STOW\/'"$NAME"'\// { print $1 }'); do
+	rm "$file"
+	while true; do
+	    file="$(dirname $file)"
+	    [ "$file" = . ] && break
+	    if [ -z "$(dir_contents $file)" ]; then
+		rmdir "$file"
+	    else
+		break
+	    fi
+	done
     done
     [ -e "$HOME/.STOW/$NAME" ] && rm "$HOME/.STOW/$NAME"
     if [ -d "$HOME/.STOW" ] \