explain_setvbuf_or_die(3) Library Functions Manual explain_setvbuf_or_die(3)NAME
explain_setvbuf_or_die - stream buffering operations and report errors
SYNOPSIS
#include <libexplain/setvbuf.h>
void explain_setvbuf_or_die(FILE *fp, char *data, int mode, size_t size);
int explain_setvbuf_on_error(FILE *fp, char *data, int mode, size_t size);
DESCRIPTION
The explain_setvbuf_or_die function is used to call the setvbuf(3) system call. On failure an explanation will be printed to stderr,
obtained from the explain_setvbuf(3) function, and then the process terminates by calling exit(EXIT_FAILURE).
The explain_setvbuf_on_error function is used to call the setvbuf(3) system call. On failure an explanation will be printed to stderr,
obtained from the explain_setvbuf(3) function, but still returns to the caller.
fp The fp, exactly as to be passed to the setvbuf(3) system call.
data The data, exactly as to be passed to the setvbuf(3) system call.
mode The mode, exactly as to be passed to the setvbuf(3) system call.
size The size, exactly as to be passed to the setvbuf(3) system call.
RETURN VALUE
The explain_setvbuf_or_die function only returns on success, see setvbuf(3) for more information. On failure, prints an explanation and
exits, it does not return.
The explain_setvbuf_on_error function always returns the value return by the wrapped setvbuf(3) system call.
EXAMPLE
The explain_setvbuf_or_die function is intended to be used in a fashion similar to the following example:
explain_setvbuf_or_die(fp, data, mode, size);
SEE ALSO setvbuf(3)
stream buffering operations
explain_setvbuf(3)
explain setvbuf(3) errors
exit(2) terminate the calling process
COPYRIGHT
libexplain version 0.52
Copyright (C) 2010 Peter Miller
explain_setvbuf_or_die(3)
Check Out this Related Man Page
SETBUF(3) BSD Library Functions Manual SETBUF(3)NAME
setbuf, setbuffer, setlinebuf, setvbuf -- stream buffering operations
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdio.h>
void
setbuf(FILE * restrict stream, char * restrict buf);
void
setbuffer(FILE *stream, char *buf, int size);
int
setlinebuf(FILE *stream);
int
setvbuf(FILE * restrict stream, char * restrict buf, int mode, size_t size);
DESCRIPTION
The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information
appears on the destination file or terminal as soon as written; when it is block buffered many characters are saved up and written as a
block; when it is line buffered characters are saved up until a newline is output or input is read from any stream attached to a terminal
device (typically stdin). The function fflush(3) may be used to force the block out early. (See fclose(3).)
Normally all files are block buffered. When the first I/O operation occurs on a file, malloc(3) is called, and an optimally-sized buffer is
obtained. If a stream refers to a terminal (as stdout normally does) it is line buffered. The standard error stream stderr is always
unbuffered. Note that these defaults may be altered using the stdbuf(1) utility.
The setvbuf() function may be used to alter the buffering behavior of a stream. The mode argument must be one of the following three macros:
_IONBF unbuffered
_IOLBF line buffered
_IOFBF fully buffered
The size argument may be given as zero to obtain deferred optimal-size buffer allocation as usual. If it is not zero, then except for
unbuffered files, the buf argument should point to a buffer at least size bytes long; this buffer will be used instead of the current buffer.
If buf is not NULL, it is the caller's responsibility to free(3) this buffer after closing the stream. (If the size argument is not zero but
buf is NULL, a buffer of the given size will be allocated immediately, and released on close. This is an extension to ANSI C; portable code
should use a size of 0 with any NULL buffer.)
The setvbuf() function may be used at any time, but may have peculiar side effects (such as discarding input or flushing output) if the
stream is ``active''. Portable applications should call it only once on any given stream, and before any I/O is performed.
The other three calls are, in effect, simply aliases for calls to setvbuf(). Except for the lack of a return value, the setbuf() function is
exactly equivalent to the call
setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
The setbuffer() function is the same, except that the size of the buffer is up to the caller, rather than being determined by the default
BUFSIZ. The setlinebuf() function is exactly equivalent to the call:
setvbuf(stream, (char *)NULL, _IOLBF, 0);
RETURN VALUES
The setvbuf() function returns 0 on success, or EOF if the request cannot be honored (note that the stream is still functional in this case).
The setlinebuf() function returns what the equivalent setvbuf() would have returned.
SEE ALSO stdbuf(1), fclose(3), fopen(3), fread(3), malloc(3), printf(3), puts(3)STANDARDS
The setbuf() and setvbuf() functions conform to ISO/IEC 9899:1990 (``ISO C90'').
BUGS
setbuf() usually uses a suboptimal buffer size and should be avoided.
BSD February 18, 2013 BSD