setbuf(), setvbuf(), setlinebuf() — assign buffering to a stream file
void setbuf(FILE *__restrict stream, char *__restrict buf);
int setvbuf(FILE *__restrict stream, char *__restrict buf, int type,
void setlinebuf(FILE *stream);
int setvbuf_unlocked(FILE *stream, char *buf, int type, size_t size);
can be used after a stream has been opened but before it
is read or written.
It causes the array pointed to by
to be used instead of an automatically allocated buffer.
pointer input/output will be completely unbuffered.
defined in the
tells how big an array is needed:
can be used after a stream has been opened
but before it is read or written.
is to be buffered.
Legal values for
causes input/output to be fully buffered.
causes output to be line buffered;
the buffer will be flushed when a newline
is written, the buffer is full, or input is requested.
causes input/output to be completely unbuffered.
When an output stream is unbuffered,
information is queued for writing on the destination file or terminal
as soon as written;
when it is buffered,
many characters are saved up and written as a block.
When the output stream is line-buffered,
each line of output is queued for writing on the destination terminal
as soon as the line is completed (that is,
as soon as a new-line character is written or terminal input is requested).
can also be used to explicitly write the buffer.
is not the
pointer, the array it points to is used for buffering
instead of an automatically allocated buffer (from
specifies the size of the buffer to be used.
is suggested as a good buffer size.
If input/output is unbuffered,
By default, output to a terminal is line buffered and
all other input/output is fully buffered.
is used to change
from block-buffered or unbuffered
can be used any time the file descriptor is active.
assigns buffering to a stream file.
If an illegal value for
setvbuf() and setvbuf_unlocked()
return a non-zero value.
Otherwise, the value returned will be zero.
A common source of error is allocating buffer space
as an "automatic" variable in a code block,
then failing to close the stream in the same block.
Allocating a buffer of
bytes does not necessarily
imply that all of
bytes are used for the buffer
were developed by HP.
setbuf(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
setvbuf(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, ANSI C