sh: Improve error handling in read builtin:

* If read -t times out, return status as if interrupted by SIGALRM
  (formerly 1).
* If a trapped signal interrupts read, return status 128+sig (formerly 1).
* If [EINTR] occurs but there is no trap, retry the read (for example
  because of a SIGWINCH in interactive mode).
* If a read error occurs, write an error message and return status 2.

As before, a variable assignment error returns 2 and discards the remaining
data read.

1 files changed, 20 insertions, 3 deletions

diff --git a/bin/sh/miscbltin.c b/bin/sh/miscbltin.c
index b81cc82..2ecd4f2 100644
--- a/bin/sh/miscbltin.c
+++ b/bin/sh/miscbltin.c
@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #include "error.h"
 #include "mystring.h"
 #include "syntax.h"
+#include "trap.h"
 
 #undef eflag
 
@@ -102,6 +103,8 @@ readcmd(int argc __unused, char **argv __unused)
 	struct timeval tv;
 	char *tvptr;
 	fd_set ifds;
+	ssize_t nread;
+	int sig;
 
 	rflag = 0;
 	prompt = NULL;
@@ -156,8 +159,10 @@ readcmd(int argc __unused, char **argv __unused)
 		/*
 		 * If there's nothing ready, return an error.
 		 */
-		if (status <= 0)
-			return(1);
+		if (status <= 0) {
+			sig = pendingsig;
+			return (128 + (sig != 0 ? sig : SIGALRM));
+		}
 	}
 
 	status = 0;
@@ -165,7 +170,19 @@ readcmd(int argc __unused, char **argv __unused)
 	backslash = 0;
 	STARTSTACKSTR(p);
 	for (;;) {
-		if (read(STDIN_FILENO, &c, 1) != 1) {
+		nread = read(STDIN_FILENO, &c, 1);
+		if (nread == -1) {
+			if (errno == EINTR) {
+				sig = pendingsig;
+				if (sig == 0)
+					continue;
+				status = 128 + sig;
+				break;
+			}
+			warning("read error: %s", strerror(errno));
+			status = 2;
+			break;
+		} else if (nread != 1) {
 			status = 1;
 			break;
 		}