missing/dup2.c

   1 /*
   2  * Public domain dup2() lookalike
   3  * by Curtis Jackson @ AT&T Technologies, Burlington, NC
   4  * electronic address:  burl!rcj
   5  *
   6  * dup2 performs the following functions:
   7  *
   8  * Check to make sure that fd1 is a valid open file descriptor.
   9  * Check to see if fd2 is already open; if so, close it.
  10  * Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
  11  * Return fd2 if all went well; return BADEXIT otherwise.
  12  */
  13
  14 #include "ruby/config.h"
  15
  16 #if defined(HAVE_FCNTL)
  17 # include <fcntl.h>
  18 #endif
  19
  20 #if !defined(HAVE_FCNTL) || !defined(F_DUPFD)
  21 # include <errno.h>
  22 #endif
  23
  24 #define BADEXIT -1
  25
  26 int
  27 dup2(int fd1, int fd2)
  28 {
  29 #if defined(HAVE_FCNTL) && defined(F_DUPFD)
  30         if (fd1 != fd2) {
  31 #ifdef F_GETFL
  32                 if (fcntl(fd1, F_GETFL) < 0)
  33                         return BADEXIT;
  34                 if (fcntl(fd2, F_GETFL) >= 0)
  35                         close(fd2);
  36 #else
  37                 close(fd2);
  38 #endif
  39                 if (fcntl(fd1, F_DUPFD, fd2) < 0)
  40                         return BADEXIT;
  41         }
  42         return fd2;
  43 #else
  44         extern int errno;
  45         int i, fd, fds[256];
  46
  47         if (fd1 == fd2) return 0;
  48         close(fd2);
  49         for (i=0; i<256; i++) {
  50                 fd = fds[i] = dup(fd1);
  51                 if (fd == fd2) break;
  52         }
  53         while (i) {
  54                 close(fds[i--]);
  55         }
  56         if (fd == fd2) return 0;
  57         errno = EMFILE;
  58         return BADEXIT;
  59 #endif
  60 }