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.1‐2017 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 follows:

        *  {_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

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.1‐2017, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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               2017                       SETVBUF(3P)

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