sort: useless use of cat

[Tobias Stoeckmann]

I see a useless use of cat in here.

Manual page:
When called with the -d option, it must decompress standard input
to standard output.

Index: file.c
===================================================================
RCS file: /cvs/src/usr.bin/sort/file.c,v
retrieving revision 1.4
diff -u -p -u -p -r1.4 file.c
--- file.c      30 Mar 2015 19:59:07 -0000      1.4
+++ file.c      31 Mar 2015 18:35:01 -0000
@@ -526,8 +526,8 @@ openfile(const char *fn, const char *mod
                        fflush(stdout);
 
                        if (mode[0] == 'r')
-                               len = sort_asprintf(&cmd, "cat %s | %s -d",
-                                   fn, compress_program);
+                               len = sort_asprintf(&cmd, "%s -d < %s",
+                                   compress_program, fn);
                        else if (mode[0] == 'w')
                                len = sort_asprintf(&cmd, "%s > %s",
                                    compress_program, fn);