ENH: try if tail works with the -n +<number> syntax, if not use only

"+<number>" (GNU tail warns that this is deprecated)

Alex

Modules/CPack.STGZ_Header.sh.in

@@ -123,15 +123,14 @@ echo ""
 # take the archive portion of this file and pipe it to tar
 # the NUMERIC parameter in this command should be one more
 # than the number of lines in this header file
-# on SunOS there are two tails, the one in /usr/bin doesn't understand
-# the -n +<number> syntax, the one in /usr/xpg4/bin/ does
-tail_executable=tail
-if [ -x /usr/xpg4/bin/tail ]
-then
-  tail_executable=/usr/xpg4/bin/tail
-fi
-
-"$tail_executable" -n +###CPACK_HEADER_LENGTH### "$0" | gunzip | (cd "${toplevel}" && tar xf -) || cpack_echo_exit "Problem unpacking the @CPACK_PACKAGE_FILE_NAME@"
+# there are tails which don't understand the "-n" argument, e.g. on SunOS
+# OTOH there are tails which complain when not using the "-n" argument (e.g. GNU)
+# so at first try to tail some file to see if tail fails if used with "-n"
+# if so, don't use "-n"
+use_new_tail_syntax="-n"
+tail $use_new_tail_syntax +1 "$0" > /dev/null 2> /dev/null || use_new_tail_syntax=""
+
+tail $use_new_tail_syntax +###CPACK_HEADER_LENGTH### "$0" | gunzip | (cd "${toplevel}" && tar xf -) || cpack_echo_exit "Problem unpacking the @CPACK_PACKAGE_FILE_NAME@"
 
 echo "Unpacking finished successfully"