gzip: fix exit status on broken pipe

Fix gzip to behave like cat etc. when outputting to a broken pipe:
i.e., exit with nonzero status if SIGPIPE is ignored, and be
terminated by SIGPIPE otherwise.
* NEWS: Mention this.
* gzip.c: Do not install signal handlers unless creating an output
file, for which signal handlers are needed.  This avoids gzip
having to deal with signal handlers when outputting to stdout.
(exiting_signal): Remove.  All uses removed.
(main): Do not install signal handlers at first.
(create_outfile): Instead, install them only when needed.
(finish_up_gzip): New function, which generalizes abort_gzip.
(abort_gzip): Use it.
* tests/pipe-output: New test.
* tests/Makefile.am (TESTS): Add it.
* util.c (EPIPE): Default to 0.
(write_error): Just warn if it is a pipe error, and suppress that
warning if quiet.  In any event exit with status 2 (warning),
not status 1 (error).
* zgrep.in: Treat gzip status 141 like status 2;
it is a broken pipe either way.

1 files changed, 7 insertions, 1 deletions

diff --git a/util.c b/util.c
index 642e620..71a937f 100644
--- a/util.c
+++ b/util.c
@@ -36,6 +36,10 @@
 #  define CHAR_BIT 8
 #endif
 
+#ifndef EPIPE
+# define EPIPE 0
+#endif
+
 static int write_buffer (int, voidp, unsigned int);
 
 /* ========================================================================
@@ -452,8 +456,10 @@ void read_error()
 
 void write_error()
 {
+  int exitcode = errno == EPIPE ? WARNING : ERROR;
+  if (! (exitcode == WARNING && quiet))
     fprintf (stderr, "\n%s: %s: %s\n", program_name, ofname, strerror (errno));
-    abort_gzip();
+  finish_up_gzip (exitcode);
 }
 
 /* ========================================================================