1 /* closeout.c - close standard output 2 3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004 Free Software 4 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 #ifdef HAVE_CONFIG_H 21 # include <config.h> 22 #endif 23 24 #include "closeout.h" 25 26 #include <stdio.h> 27 #include <stdbool.h> 28 #include <errno.h> 29 30 #include "gettext.h" 31 #define _(msgid) gettext (msgid) 32 33 #include "error.h" 34 #include "exitfail.h" 35 #include "quotearg.h" 36 #include "__fpending.h" 37 38 #if USE_UNLOCKED_IO 39 # include "unlocked-io.h" 40 #endif 41 42 static const char *file_name; 43 44 /* Set the file name to be reported in the event an error is detected 45 by close_stdout. */ 46 void 47 close_stdout_set_file_name (const char *file) 48 { 49 file_name = file; 50 } 51 52 /* Close standard output, exiting with status 'exit_failure' on failure. 53 If a program writes *anything* to stdout, that program should close 54 stdout and make sure that it succeeds before exiting. Otherwise, 55 suppose that you go to the extreme of checking the return status 56 of every function that does an explicit write to stdout. The last 57 printf can succeed in writing to the internal stream buffer, and yet 58 the fclose(stdout) could still fail (due e.g., to a disk full error) 59 when it tries to write out that buffered data. Thus, you would be 60 left with an incomplete output file and the offending program would 61 exit successfully. Even calling fflush is not always sufficient, 62 since some file systems (NFS and CODA) buffer written/flushed data 63 until an actual close call. 64 65 Besides, it's wasteful to check the return value from every call 66 that writes to stdout -- just let the internal stream state record 67 the failure. That's what the ferror test is checking below. 68 69 It's important to detect such failures and exit nonzero because many 70 tools (most notably `make' and other build-management systems) depend 71 on being able to detect failure in other tools via their exit status. */ 72 73 void 74 close_stdout (void) 75 { 76 bool prev_fail = ferror (stdout); 77 bool none_pending = (0 == __fpending (stdout)); 78 bool fclose_fail = fclose (stdout); 79 80 if (prev_fail || fclose_fail) 81 { 82 int e = fclose_fail ? errno : 0; 83 char const *write_error; 84 85 /* If ferror returned zero, no data remains to be flushed, and we'd 86 otherwise fail with EBADF due to a failed fclose, then assume that 87 it's ok to ignore the fclose failure. That can happen when a 88 program like cp is invoked like this `cp a b >&-' (i.e., with 89 stdout closed) and doesn't generate any output (hence no previous 90 error and nothing to be flushed). */ 91 if (e == EBADF && !prev_fail && none_pending) 92 return; 93 94 write_error = _("write error"); 95 if (file_name) 96 error (exit_failure, e, "%s: %s", quotearg_colon (file_name), 97 write_error); 98 else 99 error (exit_failure, e, "%s", write_error); 100 } 101 } 102