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