In gunzip(1), treat trailing garbage as a warning and not an error. This

allows scripts to distinguish it between real fatal errors, for instance a
CRC mismatch.

Update manual page for the behavior change.

PR:		bin/203873
Submitted by:	Eugene Grosbein <eugen grosbein net>
MFC after:	2 weeks

usr.bin/gzip/gzip.1

@@ -25,7 +25,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
-.Dd April 6, 2015
+.Dd October 26, 2015
 .Dt GZIP 1
 .Os
 .Sh NAME
@@ -136,7 +136,7 @@ option, allowing non-compressed data to pass through unchanged.
 .It Fl h , -help
 This option prints a usage summary and exits.
 .It Fl k , -keep
-Keep (don't delete) input files during compression
+Keep (do not delete) input files during compression
 or decompression.
 .It Fl L , -license
 This option prints
@@ -183,6 +183,12 @@ is set, it is parsed as a white-space separated list of options
 handled before any options on the command line.
 Options on the command line will override anything in
 .Ev GZIP .
+.Sh EXIT STATUS
+The
+.Nm
+utility exits 0 on success,
+1 on errors,
+and 2 if a warning occurs.
 .Sh SEE ALSO
 .Xr bzip2 1 ,
 .Xr compress 1 ,
@@ -220,7 +226,7 @@ with unpack support written by
 .An Xin LI Aq Mt delphij@FreeBSD.org .
 .Sh BUGS
 According to RFC 1952, the recorded file size is stored in a 32-bit
-integer, therefore, it can not represent files larger than 4GB.
+integer, therefore, it cannot represent files larger than 4GB.
 This limitation also applies to
 .Fl l
 option of

usr.bin/gzip/gzip.c

@@ -810,6 +810,7 @@ gz_uncompress(int in, int out, char *pre, size_t prelen, off_t *gsizep,
 				if (in_tot > 0) {
 					maybe_warnx("%s: trailing garbage "
 						    "ignored", filename);
+					exit_value = 2;
 					goto stop;
 				}
 				maybe_warnx("input not gziped (MAGIC0)");