/* closeout.c - close standard output and standard error Copyright (C) 1998-2007, 2012, 2015 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . */ #include /* Specification. */ #include "closeout.h" #include #include #include #include "error.h" #include "fwriteerror.h" #include "gettext.h" #define _(msgid) gettext (msgid) /* Close standard output, exiting with status STATUS on failure. If a program writes *anything* to stdout, that program should close stdout and make sure that it succeeds before exiting. Otherwise, suppose that you go to the extreme of checking the return status of every function that does an explicit write to stdout. The last printf can succeed in writing to the internal stream buffer, and yet the fclose(stdout) could still fail (due e.g., to a disk full error) when it tries to write out that buffered data. Thus, you would be left with an incomplete output file and the offending program would exit successfully. Even calling fflush is not always sufficient, since some file systems (NFS and CODA) buffer written/flushed data until an actual close call. Besides, it's wasteful to check the return value from every call that writes to stdout -- just let the internal stream state record the failure. That's what the ferror test is checking below. If the stdout file descriptor was initially closed (such as when executing a program through "program 1>&-"), it is a failure if and only if some output was made to stdout. Likewise for standard error. It's important to detect such failures and exit nonzero because many tools (most notably 'make' and other build-management systems) depend on being able to detect failure in other tools via their exit status. */ /* Close standard output and standard error, exiting with status EXIT_FAILURE on failure. */ void close_stdout (void) { /* Close standard output. */ if (fwriteerror_no_ebadf (stdout)) error (EXIT_FAILURE, errno, "%s", _("write error")); /* Close standard error. This is simpler than fwriteerror_no_ebadf, because upon failure we don't need an errno - all we can do at this point is to set an exit status. */ errno = 0; if (ferror (stderr) || fflush (stderr)) { fclose (stderr); exit (EXIT_FAILURE); } if (fclose (stderr) && errno != EBADF) exit (EXIT_FAILURE); } /* Note: When exit (...) calls the atexit-registered close_stdout (), which calls error (status, ...), which calls exit (status), we have undefined behaviour according to ISO C 99 section 7.20.4.3.(2). But in practice there is no problem: The second exit call is executed at a moment when the atexit handlers are no longer active. */