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authorPaul Eggert <eggert@cs.ucla.edu>2006-07-22 22:26:04 +0000
committerPaul Eggert <eggert@cs.ucla.edu>2006-07-22 22:26:04 +0000
commit2df2295d68f2471038ab3c52e828430e23f9db15 (patch)
tree8f2f2061175b777047fff6e053afde15fd92f151
parent0971f7f44aafa49acc313ed6919319ec00edd697 (diff)
downloadcoreutils-2df2295d68f2471038ab3c52e828430e23f9db15.tar.xz
Initial revision.
-rw-r--r--lib/close-stream.c78
-rw-r--r--lib/close-stream.h2
-rw-r--r--m4/close-stream.m413
3 files changed, 93 insertions, 0 deletions
diff --git a/lib/close-stream.c b/lib/close-stream.c
new file mode 100644
index 000000000..d7551d67f
--- /dev/null
+++ b/lib/close-stream.c
@@ -0,0 +1,78 @@
+/* Close a stream, with nicer error checking than fclose's.
+
+ Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006 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 2, 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, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "close-stream.h"
+
+#include <errno.h>
+#include <stdbool.h>
+
+#include "__fpending.h"
+
+#if USE_UNLOCKED_IO
+# include "unlocked-io.h"
+#endif
+
+/* Close STREAM. Return 0 if successful, EOF (setting errno)
+ otherwise. A failure might set errno to 0 if the error number
+ cannot be determined.
+
+ If a program writes *anything* to STREAM, that program should close
+ STREAM 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 STREAM. The last
+ printf can succeed in writing to the internal stream buffer, and yet
+ the fclose(STREAM) 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 STREAM -- just let the internal stream state record
+ the failure. That's what the ferror test is checking below. */
+
+int
+close_stream (FILE *stream)
+{
+ bool some_pending = (__fpending (stream) != 0);
+ bool prev_fail = (ferror (stream) != 0);
+ bool fclose_fail = (fclose (stream) != 0);
+
+ /* Return an error indication if there was a previous failure or if
+ fclose failed, with one exception: ignore an fclose failure if
+ there was no previous error, no data remains to be flushed, and
+ fclose failed with EBADF. That can happen when a program like cp
+ is invoked like this `cp a b >&-' (i.e., with standard output
+ closed) and doesn't generate any output (hence no previous error
+ and nothing to be flushed). */
+
+ if (prev_fail || (fclose_fail && (some_pending || errno != EBADF)))
+ {
+ if (! fclose_fail)
+ errno = 0;
+ return EOF;
+ }
+
+ return 0;
+}
diff --git a/lib/close-stream.h b/lib/close-stream.h
new file mode 100644
index 000000000..be3d4196b
--- /dev/null
+++ b/lib/close-stream.h
@@ -0,0 +1,2 @@
+#include <stdio.h>
+int close_stream (FILE *stream);
diff --git a/m4/close-stream.m4 b/m4/close-stream.m4
new file mode 100644
index 000000000..93f4d9a91
--- /dev/null
+++ b/m4/close-stream.m4
@@ -0,0 +1,13 @@
+dnl Copyright (C) 2006 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_CLOSE_STREAM],
+[
+ AC_LIBSOURCES([close-stream.c, close-stream.h])
+ AC_LIBOBJ([close-stream])
+
+ dnl Prerequisites of lib/close-stream.c.
+ :
+])