Replace home-grown dup2() implementation with actual dup2() calls. This

should slightly reduce the number of system calls in critical portions of
the shell, and select a more efficient path through the fdalloc code.

Reviewed by:	bde

bin/sh/eval.c

@@ -479,16 +479,14 @@ evalpipe(union node *n)
 		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
 			INTON;
 			if (prevfd > 0) {
-				close(0);
-				copyfd(prevfd, 0);
+				dup2(prevfd, 0);
 				close(prevfd);
 			}
 			if (pip[1] >= 0) {
 				if (!(prevfd >= 0 && pip[0] == 0))
 					close(pip[0]);
 				if (pip[1] != 1) {
-					close(1);
-					copyfd(pip[1], 1);
+					dup2(pip[1], 1);
 					close(pip[1]);
 				}
 			}
@@ -545,8 +543,7 @@ evalbackcmd(union node *n, struct backcmd *result)
 			FORCEINTON;
 			close(pip[0]);
 			if (pip[1] != 1) {
-				close(1);
-				copyfd(pip[1], 1);
+				dup2(pip[1], 1);
 				close(pip[1]);
 			}
 			evaltree(n, EV_EXIT);
@@ -742,8 +739,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 			FORCEINTON;
 			close(pip[0]);
 			if (pip[1] != 1) {
-				close(1);
-				copyfd(pip[1], 1);
+				dup2(pip[1], 1);
 				close(pip[1]);
 			}
 		}

bin/sh/input.c

@@ -388,7 +388,7 @@ setinputfile(char *fname, int push)
 	if ((fd = open(fname, O_RDONLY)) < 0)
 		error("Can't open %s: %s", fname, strerror(errno));
 	if (fd < 10) {
-		fd2 = copyfd(fd, 10);
+		fd2 = fcntl(fd, F_DUPFD, 10);
 		close(fd);
 		if (fd2 < 0)
 			error("Out of file descriptors");

bin/sh/parser.c

@@ -48,7 +48,6 @@ __FBSDID("$FreeBSD$");
 #include "parser.h"
 #include "nodes.h"
 #include "expand.h"	/* defines rmescapes() */
-#include "redir.h"	/* defines copyfd() */
 #include "syntax.h"
 #include "options.h"
 #include "input.h"

bin/sh/redir.c

@@ -182,8 +182,7 @@ openredirect(union node *redir, char memory[10])
 			error("cannot open %s: %s", fname, strerror(errno));
 movefd:
 		if (f != fd) {
-			close(fd);
-			copyfd(f, fd);
+			dup2(f, fd);
 			close(f);
 		}
 		break;
@@ -215,12 +214,11 @@ openredirect(union node *redir, char memory[10])
 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
 			if (memory[redir->ndup.dupfd])
 				memory[fd] = 1;
-			else {
-				close(fd);
-				copyfd(redir->ndup.dupfd, fd);
-			}
-		} else
+			else
+				dup2(redir->ndup.dupfd, fd);
+		} else {
 			close(fd);
+		}
 		break;
 	case NHERE:
 	case NXHERE:
@@ -288,10 +286,11 @@ popredir(void)
 		if (rp->renamed[i] != EMPTY) {
                         if (i == 0)
                                 fd0_redirected--;
-			close(i);
 			if (rp->renamed[i] >= 0) {
-				copyfd(rp->renamed[i], i);
+				dup2(rp->renamed[i], i);
 				close(rp->renamed[i]);
+			} else {
+				close(i);
 			}
 		}
 	}
@@ -346,26 +345,3 @@ clearredir(void)
 		}
 	}
 }
-
-
-
-/*
- * Copy a file descriptor to be >= to.  Returns -1
- * if the source file descriptor is closed, EMPTY if there are no unused
- * file descriptors left.
- */
-
-int
-copyfd(int from, int to)
-{
-	int newfd;
-
-	newfd = fcntl(from, F_DUPFD, to);
-	if (newfd < 0) {
-		if (errno == EMFILE)
-			return EMPTY;
-		else
-			error("%d: %s", from, strerror(errno));
-	}
-	return newfd;
-}

bin/sh/redir.h

@@ -46,5 +46,4 @@ void redirect(union node *, int);
 void popredir(void);
 int fd0_redirected_p(void);
 void clearredir(void);
-int copyfd(int, int);