[Quilt-dev] [PATCH 38/39] backup-files: Keep /dev/null opened

[Jean Delvare]

Keep /dev/null opened as we will need it repeatedly. Avoiding
repeated calls to open brings a small performance boost.

Signed-off-by: Jean Delvare <address@hidden>
Reviewed-by: Raphael Hertzog <address@hidden>
---
 quilt/scripts/backup-files.in |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

--- a/quilt/scripts/backup-files.in
+++ b/quilt/scripts/backup-files.in
@@ -1,6 +1,8 @@
 #! @BASH@
 
 set -e
+# Keep /dev/null opened as we will need it repeatedly
+exec 4> /dev/null
 
 # Copyright (C) 2006 Steve Langasek <address@hidden>
 # Copyright (C) 2011 Jean Delvare <address@hidden>
@@ -78,7 +80,7 @@ backup() {
                if [ -n "$OPT_NOLINKS" -a "$(stat @STAT_HARDLINK@ "$file")" = 1 
]; then
                        cp -p "$file" "$backup"
                else
-                       ln "$file" "$backup" 2> /dev/null || cp -p "$file" 
"$backup"
+                       ln "$file" "$backup" 2>&4 || cp -p "$file" "$backup"
                        if [ -n "$OPT_NOLINKS" ]; then
                                ensure_nolinks "$file"
                        fi
@@ -104,7 +106,7 @@ restore()
                else
                        mkdir -p "$(dirname "$file")"
                fi
-               ln "$backup" "$file" 2> /dev/null || cp -p "$backup" "$file"
+               ln "$backup" "$file" 2>&4 || cp -p "$backup" "$file"
 
                if [ -n "$OPT_TOUCH" ]; then
                        touch "$file"
@@ -118,7 +120,7 @@ restore()
 
        if [ -z "$OPT_KEEP_BACKUP" ]; then
                rm "$backup"
-               rmdir -p "${backup%/*}" 2> /dev/null || true
+               rmdir -p "${backup%/*}" 2>&4 || true
        fi
 }
 
@@ -154,7 +156,7 @@ restore_all()
                if (cd "$OPT_PREFIX" && \
                    xargs -0 cp -l --parents --remove-destination \
                                --target-directory="$target_dir" \
-                               < "$NONEMPTY_FILES" 2> /dev/null); then
+                               < "$NONEMPTY_FILES" 2>&4); then
                        while read -d $'\0' -r
                        do
                                $ECHO "Restoring ${REPLY#./}"
@@ -171,7 +173,7 @@ restore_all()
                                local backup=$OPT_PREFIX$file
 
                                $ECHO "Restoring $file"
-                               ln "$backup" "$file" 2> /dev/null || cp -p 
"$backup" "$file"
+                               ln "$backup" "$file" 2>&4 || cp -p "$backup" 
"$file"
                        done < "$NONEMPTY_FILES"
                fi
 
@@ -240,7 +242,7 @@ copy_many()
                # fallback to per-file processing, which always works.
 
                if xargs -0 cp -p --parents --target-directory="$OPT_PREFIX" \
-                  < "$NONEMPTY_FILES" 2> /dev/null; then
+                  < "$NONEMPTY_FILES" 2>&4; then
                        while read -d $'\0' -r
                        do
                                $ECHO "Copying $REPLY"
@@ -258,7 +260,7 @@ copy_many()
 some_files_have_links()
 {
        (cd "$OPT_PREFIX" && find . -type f -print0) \
-       | xargs -0 stat @STAT_HARDLINK@ 2> /dev/null | grep -qv '^1$'
+       | xargs -0 stat @STAT_HARDLINK@ 2>&4 | grep -qv '^1$'
 }