sh: Check whether dup2 was successful for >&FD and <&FD.

A failure (usually caused by FD not being open) is a redirection error.

Exp-run done by:	pav (with some other sh(1) changes)

1 files changed, 5 insertions, 2 deletions

diff --git a/bin/sh/redir.c b/bin/sh/redir.c
index f3ad3af..4f0a40c 100644
--- a/bin/sh/redir.c
+++ b/bin/sh/redir.c
@@ -217,8 +217,11 @@ movefd:
 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
 			if (memory[redir->ndup.dupfd])
 				memory[fd] = 1;
-			else
-				dup2(redir->ndup.dupfd, fd);
+			else {
+				if (dup2(redir->ndup.dupfd, fd) < 0)
+					error("%d: %s", redir->ndup.dupfd,
+							strerror(errno));
+			}
 		} else {
 			close(fd);
 		}