setvbuf(3p) — Linux manual page


SETVBUF(3P)               POSIX Programmer's Manual              SETVBUF(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       setvbuf — assign buffering to a stream

SYNOPSIS         top

       #include <stdio.h>

       int setvbuf(FILE *restrict stream, char *restrict buf, int type,
           size_t size);

DESCRIPTION         top

       The functionality described on this reference page is aligned with
       the ISO C standard. Any conflict between the requirements described
       here and the ISO C standard is unintentional. This volume of
       POSIX.1‐2008 defers to the ISO C standard.

       The setvbuf() function may be used after the stream pointed to by
       stream is associated with an open file but before any other operation
       (other than an unsuccessful call to setvbuf()) is performed on the
       stream. The argument type determines how stream shall be buffered, as

        *  {_IOFBF} shall cause input/output to be fully buffered.

        *  {_IOLBF} shall cause input/output to be line buffered.

        *  {_IONBF} shall cause input/output to be unbuffered.

       If buf is not a null pointer, the array it points to may be used
       instead of a buffer allocated by setvbuf() and the argument size
       specifies the size of the array; otherwise, size may determine the
       size of a buffer allocated by the setvbuf() function. The contents of
       the array at any time are unspecified.

       For information about streams, see Section 2.5, Standard I/O Streams.

RETURN VALUE         top

       Upon successful completion, setvbuf() shall return 0. Otherwise, it
       shall return a non-zero value if an invalid value is given for type
       or if the request cannot be honored, and may set errno to indicate
       the error.

ERRORS         top

       The setvbuf() function may fail if:

       EBADF  The file descriptor underlying stream is not valid.

       The following sections are informative.

EXAMPLES         top



       A common source of error is allocating buffer space as an
       ``automatic'' variable in a code block, and then failing to close the
       stream in the same block.

       With setvbuf(), allocating a buffer of size bytes does not
       necessarily imply that all of size bytes are used for the buffer

       Applications should note that many implementations only provide line
       buffering on input from terminal devices.

RATIONALE         top




SEE ALSO         top

       Section 2.5, Standard I/O Streams, fopen(3p), setbuf(3p)

       The Base Definitions volume of POSIX.1‐2008, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see .

IEEE/The Open Group                 2013                         SETVBUF(3P)

Pages that refer to this page: stdio.h(0p)cat(1p)setbuf(3p)stderr(3p)stdin(3p)stdout(3p)