dlopen.3: Note that symbol use might keep a dlclose'd object in memory

[thirdparty/man-pages.git] / man3 / ferror.3

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.\"     @(#)ferror.3	6.8 (Berkeley) 6/29/91
.\"
.\"
.\" Converted for Linux, Mon Nov 29 14:24:40 1993, faith@cs.unc.edu
.\" Added remark on EBADF for fileno, aeb, 2001-03-22
.\"
.TH FERROR 3  2019-03-06 "" "Linux Programmer's Manual"
.SH NAME
clearerr, feof, ferror, fileno \- check and reset stream status
.SH SYNOPSIS
.B #include <stdio.h>
.PP
.BI "void clearerr(FILE *" stream );
.PP
.BI "int feof(FILE *" stream );
.PP
.BI "int ferror(FILE *" stream );
.PP
.BI "int fileno(FILE *" stream );
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.BR fileno ():
_POSIX_C_SOURCE
.SH DESCRIPTION
The function
.BR clearerr ()
clears the end-of-file and error indicators for the stream pointed to by
.IR stream .
.PP
The function
.BR feof ()
tests the end-of-file indicator for the stream pointed to by
.IR stream ,
returning nonzero if it is set.
The end-of-file indicator can be cleared only by the function
.BR clearerr ().
.PP
The function
.BR ferror ()
tests the error indicator for the stream pointed to by
.IR stream ,
returning nonzero if it is set.
The error indicator can be reset only by the
.BR clearerr ()
function.
.PP
The function
.BR fileno ()
examines the argument
.I stream
and returns the integer file descriptor used to implement this stream.
The file descriptor is still owned by
.I stream
and will be closed when
.BR fclose (3)
is called.
Duplicate the file descriptor with
.BR dup (2)
before passing it to code that might close it.
.PP
For nonlocking counterparts, see
.BR unlocked_stdio (3).
.SH ERRORS
These functions should not fail and do not set the external variable
.IR errno .
(However, in case
.BR fileno ()
detects that its argument is not a valid stream, it must
return \-1 and set
.I errno
to
.BR EBADF .)
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw19 lb lb
l l l.
Interface	Attribute	Value
T{
.BR clearerr (),
.BR feof (),
.br
.BR ferror (),
.BR fileno ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
The functions
.BR clearerr (),
.BR feof (),
and
.BR ferror ()
conform to C89, C99, POSIX.1-2001, and POSIX.1-2008.
.PP
The function
.BR fileno ()
conforms to POSIX.1-2001 and POSIX.1-2008.
.SH SEE ALSO
.BR open (2),
.BR fdopen (3),
.BR stdio (3),
.BR unlocked_stdio (3)