- Fix for valid empty LESSOPEN pipe output

Resolves: #579251, #615303

less-436-empty-lessopen-pipe.patch

@@ -0,0 +1,39 @@
+--- less-436/filename.c	2009-07-06 22:52:23.000000000 +0200
++++ less-436_vvitek/filename.c	2010-12-08 16:01:41.269695932 +0100
+@@ -879,17 +879,32 @@ open_altfile(filename, pf, pfd)
+ 		 */
+ 		f = fileno(fd);
+ 		SET_BINARY(f);
++		*pfd = (void *) fd;
++		*pf = f;
+ 		if (read(f, &c, 1) != 1)
+ 		{
+ 			/*
+-			 * Pipe is empty.  This means there is no alt file.
++			 * Error or pipe is empty. Close it and
++			 * check exit status of the pipe process.
+ 			 */
+-			pclose(fd);
++			if (pclose(fd) == 0) {
++				/*
++				 * Exit status was zero, so the EOF was correct
++				 * empty output. Let the program open /dev/null
++				 * instead, as the pipe is already closed.
++				 * Set force_open to omit bad_file() check
++				 * failure, as it is special 'c' pseudo-device.
++				 */
++				*pf = 0;
++				*pfd = NULL;
++				force_open = 1;
++				return (save("/dev/null"));
++			}
++			*pf = 0;
++			*pfd = NULL;
+ 			return (NULL);
+ 		}
+ 		ch_ungetchar(c);
+-		*pfd = (void *) fd;
+-		*pf = f;
+ 		return (save("-"));
+ 	}
+ #endif

less.spec

@@ -12,6 +12,7 @@ Patch1:	less-406-Foption.patch
 Patch4: less-394-time.patch
 Patch5: less-418-fsync.patch
 Patch6: less-436-manpage.patch
+Patch7: less-436-empty-lessopen-pipe.patch
 URL: http://www.greenwoodsoftware.com/less/
 Buildroot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n) 
 BuildRequires: ncurses-devel
@@ -34,6 +35,7 @@ files, and you'll use it frequently.
 %patch4 -p1 -b .time
 %patch5 -p1 -b .fsync
 %patch6 -p1 -b .manpage
+%patch7 -p1 -b .empty-lessopen-pipe
 
 autoreconf
 
@@ -65,6 +67,10 @@ ls -la $RPM_BUILD_ROOT/etc/profile.d
 rm -rf $RPM_BUILD_ROOT
 
 %changelog
+* Tue Dec 21 2010 Vojtech Vitek (V-Teq) <vvitek@redhat.com> - 436-7
+- Fix for valid empty LESSOPEN pipe output 
+  Resolves: #579251, #615303
+
 * Wed Jan 20 2010 Nikola Pajkovsky <npajkovs@redhat.com> - 436-6
 - RFE: lesspipe.sh could use a support for *.xz file
 

lesspipe.sh

@@ -2,15 +2,19 @@
 #
 # To use this filter with less, define LESSOPEN:
 # export LESSOPEN="|/usr/bin/lesspipe.sh %s"
+#
+# Script should return zero on success. This is important in case
+# of empty output of any decompressor when the output pipe produces
+# just EOF (eg. while uncompressing gzipped empty file).
 
 lesspipe() {
   case "$1" in
   *.[1-9n]|*.man|*.[1-9n].bz2|*.man.bz2|*.[1-9].gz|*.[1-9]x.gz|*.man.gz|*.[1-9].xz|*.[1-9]x.xz|*.man.xz)
 	case "$1" in
-		*.gz)	DECOMPRESSOR="gunzip -c" ;;
-		*.bz2)	DECOMPRESSOR="bunzip2 -c" ;;
-		*)	DECOMPRESSOR="cat" ;;
+		*.gz)	DECOMPRESSOR="gzip -dc" ;;
+		*.bz2)	DECOMPRESSOR="bzip2 -dc" ;;
 	esac
+	if [ ! -z $DECOMPRESSOR ] ; then
 	    if $DECOMPRESSOR -- "$1" | file - | grep -q troff; then
 		    if echo "$1" | grep -q ^/; then	#absolute path
 			    man -- "$1" | cat -s
@@ -19,6 +23,9 @@ lesspipe() {
 		    fi
 	    else
 		    $DECOMPRESSOR -- "$1"
+	    fi
+	else
+	    exit 1
 	fi ;;
   *.tar) tar tvvf "$1" ;;
   *.tgz|*.tar.gz|*.tar.[zZ]) tar tzvvf "$1" ;;
@@ -41,19 +48,18 @@ lesspipe() {
 		echo "Install ImageMagick or GraphicsMagick to browse images"
 	fi ;;
   *)
-	case "$1" in
-		*.gz)	DECOMPRESSOR="gunzip -c" ;;
-		*.bz2)	DECOMPRESSOR="bunzip2 -c" ;;
-		*.xz)	DECOMPRESSOR="unxz -c" ;;
-	esac
-	if [ ! -z $DECOMPRESSOR ] ; then
-		$DECOMPRESSOR -- "$1" ;
-	fi
+	exit 1
   esac
+  exit $?
 }
 
+if [ ! -e "$1" ] ; then
+	exit 1
+fi
+
 if [ -d "$1" ] ; then
 	/bin/ls -alF -- "$1"
+	exit $?
 else
 	lesspipe "$1" 2> /dev/null
 fi