1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file tuklib_open_stdxxx.c 4 /// \brief Make sure that file descriptors 0, 1, and 2 are open 5 // 6 // Author: Lasse Collin 7 // 8 // This file has been put into the public domain. 9 // You can do whatever you want with this file. 10 // 11 /////////////////////////////////////////////////////////////////////////////// 12 13 #include "tuklib_open_stdxxx.h" 14 15 #ifndef TUKLIB_DOSLIKE 16 # include <stdlib.h> 17 # include <errno.h> 18 # include <fcntl.h> 19 # include <unistd.h> 20 #endif 21 22 23 extern void 24 tuklib_open_stdxxx(int err_status) 25 { 26 #ifdef TUKLIB_DOSLIKE 27 // Do nothing, just silence warnings. 28 (void)err_status; 29 30 #else 31 for (int i = 0; i <= 2; ++i) { 32 // We use fcntl() to check if the file descriptor is open. 33 if (fcntl(i, F_GETFD) == -1 && errno == EBADF) { 34 // With stdin, we could use /dev/full so that 35 // writing to stdin would fail. However, /dev/full 36 // is Linux specific, and if the program tries to 37 // write to stdin, there's already a problem anyway. 38 const int fd = open("/dev/null", O_NOCTTY 39 | (i == 0 ? O_WRONLY : O_RDONLY)); 40 41 if (fd != i) { 42 if (fd != -1) 43 (void)close(fd); 44 45 // Something went wrong. Exit with the 46 // exit status we were given. Don't try 47 // to print an error message, since stderr 48 // may very well be non-existent. This 49 // error should be extremely rare. 50 exit(err_status); 51 } 52 } 53 } 54 #endif 55 56 return; 57 } 58