1 /* Close a stream, with nicer error checking than fclose's. 2 3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006 Free 4 Software Foundation, Inc. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program; if not, write to the Free Software Foundation, 18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 19 20 #include <config.h> 21 22 #include "close-stream.h" 23 24 #include <errno.h> 25 #include <stdbool.h> 26 27 #include "__fpending.h" 28 29 #if USE_UNLOCKED_IO 30 # include "unlocked-io.h" 31 #endif 32 33 /* Close STREAM. Return 0 if successful, EOF (setting errno) 34 otherwise. A failure might set errno to 0 if the error number 35 cannot be determined. 36 37 If a program writes *anything* to STREAM, that program should close 38 STREAM and make sure that it succeeds before exiting. Otherwise, 39 suppose that you go to the extreme of checking the return status 40 of every function that does an explicit write to STREAM. The last 41 printf can succeed in writing to the internal stream buffer, and yet 42 the fclose(STREAM) could still fail (due e.g., to a disk full error) 43 when it tries to write out that buffered data. Thus, you would be 44 left with an incomplete output file and the offending program would 45 exit successfully. Even calling fflush is not always sufficient, 46 since some file systems (NFS and CODA) buffer written/flushed data 47 until an actual close call. 48 49 Besides, it's wasteful to check the return value from every call 50 that writes to STREAM -- just let the internal stream state record 51 the failure. That's what the ferror test is checking below. */ 52 53 int 54 close_stream (FILE *stream) 55 { 56 bool some_pending = (__fpending (stream) != 0); 57 bool prev_fail = (ferror (stream) != 0); 58 bool fclose_fail = (fclose (stream) != 0); 59 60 /* Return an error indication if there was a previous failure or if 61 fclose failed, with one exception: ignore an fclose failure if 62 there was no previous error, no data remains to be flushed, and 63 fclose failed with EBADF. That can happen when a program like cp 64 is invoked like this `cp a b >&-' (i.e., with standard output 65 closed) and doesn't generate any output (hence no previous error 66 and nothing to be flushed). */ 67 68 if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) 69 { 70 if (! fclose_fail) 71 errno = 0; 72 return EOF; 73 } 74 75 return 0; 76 }