Python/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 <fcntl.h>
  15
  16 #define BADEXIT -1
  17
  18 int
  19 dup2(int fd1, int fd2)
  20 {
  21         if (fd1 != fd2) {
  22                 if (fcntl(fd1, F_GETFL) < 0)
  23                         return BADEXIT;
  24                 if (fcntl(fd2, F_GETFL) >= 0)
  25                         close(fd2);
  26                 if (fcntl(fd1, F_DUPFD, fd2) < 0)
  27                         return BADEXIT;
  28         }
  29         return fd2;
  30 }