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glibc  2.9
dup2.c
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00001 /* Copyright (C) 1991, 92, 93, 95, 96, 97, 2002 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public
00006    License as published by the Free Software Foundation; either
00007    version 2.1 of the License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; if not, write to the Free
00016    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00017    02111-1307 USA.  */
00018 
00019 #include <errno.h>
00020 #include <fcntl.h>
00021 #include <limits.h>
00022 #include <unistd.h>
00023 
00024 /* Duplicate FD to FD2, closing the old FD2 and making FD2 be
00025    open the same file as FD is.  Return FD2 or -1.  */
00026 int
00027 __dup2 (fd, fd2)
00028      int fd;
00029      int fd2;
00030 {
00031   int save;
00032 
00033   if (fd2 < 0
00034 #ifdef OPEN_MAX
00035       || fd2 >= OPEN_MAX
00036 #endif
00037 )
00038     {
00039       __set_errno (EBADF);
00040       return -1;
00041     }
00042 
00043   /* Check if FD is kosher.  */
00044   if (fcntl (fd, F_GETFL) < 0)
00045     return -1;
00046 
00047   if (fd == fd2)
00048     return fd2;
00049 
00050   /* This is not atomic.  */
00051 
00052   save = errno;
00053   (void) close (fd2);
00054   __set_errno (save);
00055 
00056   return fcntl (fd, F_DUPFD, fd2);
00057 }
00058 libc_hidden_def (__dup2)
00059 weak_alias (__dup2, dup2)