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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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SETVBUF(3P) POSIX Programmer's Manual SETVBUF(3P)
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.
setvbuf — assign buffering to a stream
#include <stdio.h>
int setvbuf(FILE *restrict stream, char *restrict buf, int type,
size_t size);
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
Streams.
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.
The setvbuf() function may fail if:
EBADF The file descriptor underlying stream is not valid.
The following sections are informative.
None.
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
area.
Applications should note that many implementations only provide
line buffering on input from terminal devices.
None.
None.
Section 2.5, Standard I/O Streams, fopen(3p), setbuf(3p)
The Base Definitions volume of POSIX.1‐2017, stdio.h(0p)
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 http://www.opengroup.org/unix/online.html .
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
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 SETVBUF(3P)
Pages that refer to this page: stdio.h(0p), cat(1p), setbuf(3p), stdin(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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