Use exit status 2 to indicate that the file was not compressed because

its size would not be reduced (SUSv3).

usr.bin/compress/compress.1

@@ -150,6 +150,13 @@ coding (as used in the historical command compact), and takes less
 time to compute.
 .Sh DIAGNOSTICS
 .Ex -std compress uncompress
+.Pp
+The
+.Nm compress
+utility exits 2 if attempting to compress the file would not reduce its size
+and the
+.Fl f
+option was not specified.
 .Sh SEE ALSO
 .Xr gunzip 1 ,
 .Xr gzexe 1 ,

usr.bin/compress/compress.c

@@ -249,6 +249,7 @@ compress(in, out, bits)
 		if (!force && sb.st_size >= isb.st_size) {
 			if (verbose)
 		(void)printf("%s: file would grow; left unmodified\n", in);
+			eval = 2;
 			if (unlink(out))
 				cwarn("%s", out);
 			goto err;