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-rw-r--r--missing/dup2.c69
1 files changed, 47 insertions, 22 deletions
diff --git a/missing/dup2.c b/missing/dup2.c
index c541149..e7cc46f 100644
--- a/missing/dup2.c
+++ b/missing/dup2.c
@@ -1,36 +1,61 @@
-/*
- * Copyright (c) 1991, Larry Wall
+/*
+ * Public domain dup2() lookalike
+ * by Curtis Jackson @ AT&T Technologies, Burlington, NC
+ * electronic address: burl!rcj
*
- * You may distribute under the terms of either the GNU General Public
- * License or the Artistic License, as specified in the README file.
+ * dup2 performs the following functions:
+ *
+ * Check to make sure that fd1 is a valid open file descriptor.
+ * Check to see if fd2 is already open; if so, close it.
+ * Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
+ * Return fd2 if all went well; return BADEXIT otherwise.
*/
-#include "defines.h"
+#include "config.h"
-#if defined(HAVE_FCNTL) && defined(F_DUPFD)
+#if defined(HAVE_FCNTL)
# include <fcntl.h>
#endif
+#if !defined(HAVE_FCNTL) || !defined(F_DUPFD)
+# include <errno.h>
+#endif
+
+#define BADEXIT -1
+
int
-dup2(oldfd,newfd)
-int oldfd;
-int newfd;
+dup2(fd1, fd2)
+int fd1, fd2;
{
#if defined(HAVE_FCNTL) && defined(F_DUPFD)
- close(newfd);
- return fcntl(oldfd, F_DUPFD, newfd);
+ if (fd1 != fd2) {
+#ifdef F_GETFL
+ if (fcntl(fd1, F_GETFL) < 0)
+ return BADEXIT;
+ if (fcntl(fd2, F_GETFL) >= 0)
+ close(fd2);
+#else
+ close(fd2);
+#endif
+ if (fcntl(fd1, F_DUPFD, fd2) < 0)
+ return BADEXIT;
+ }
+ return fd2;
#else
- int fdtmp[256];
- int fdx = 0;
- int fd;
+ extern int errno;
+ int i, fd, fds[256];
- if (oldfd == newfd)
- return 0;
- close(newfd);
- while ((fd = dup(oldfd)) != newfd) /* good enough for low fd's */
- fdtmp[fdx++] = fd;
- while (fdx > 0)
- close(fdtmp[--fdx]);
- return 0;
+ if (fd1 == fd2) return 0;
+ close(fd2);
+ for (i=0; i<256; i++) {
+ fd = fds[i] = dup(fd1);
+ if (fd == fd2) break;
+ }
+ while (i) {
+ close(fds[i--]);
+ }
+ if (fd == fd2) return 0;
+ errno = EMFILE;
+ return BADEXIT;
#endif
}