xzless: Support compressed standard input

It can be somewhat confusing that

	less < some_file.txt

works fine, whereas

	xzless < some_file.txt.xz

does not.  Since version 429, ‘less’ allows a filter specified in
the LESSOPEN environment variable to preprocess its input even if
it comes from standard input, if $LESSOPEN begins with ‘|-’.  So
set $LESSOPEN to take advantage of this feature.

Check less’s version at runtime so xzless can continue to work
with older versions.

diff --git a/src/scripts/xzless.in b/src/scripts/xzless.in
index 6639943..a3da697 100644 (file)
--- a/src/scripts/xzless.in
+++ b/src/scripts/xzless.in
@@ -46,7 +46,13 @@ if test "${LESSMETACHARS+set}" != set; then
        LESSMETACHARS="$space$tab$nl'"';*?"()<>[|&^`#\$%=~'
 fi
 
-LESSOPEN="|$xz -cdfq -- %s"
+if test "$(less -V | { read ver && echo ${ver#less }; })" -ge 429; then
+       # less 429 or later: LESSOPEN pipe will be used on
+       # standard input if $LESSOPEN begins with |-.
+       LESSOPEN="|-$xz -cdfq -- %s"
+else
+       LESSOPEN="|$xz -cdfq -- %s"
+fi
 export LESSMETACHARS LESSOPEN
 
 exec less "$@"