NAME
setbuf — assign
buffering to a stream
SYNOPSIS
#include
<stdio.h>
void setbuf(FILE *restrict stream, char *restrict buf);
DESCRIPTION
[CX] 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.1-2024 defers to the ISO C standard.
Except that it returns no value, the function call:
setbuf(stream, buf)
shall be equivalent to:
setvbuf(stream, buf, _IOFBF, BUFSIZ)
if buf is not a null pointer, or to:
setvbuf(stream, buf, _IONBF, BUFSIZ)
if buf is a null pointer.
RETURN VALUE
The setbuf () function shall not return a
value.
ERRORS
Although the setvbuf(3) interface may set
errno in defined ways, the value of
errno after a call to setbuf () is
unspecified.
EXAMPLES
None.
APPLICATION USAGE
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 setbuf (), allocating a buffer of
BUFSIZ bytes does not necessarily imply that all of BUFSIZ bytes are used
for the buffer area.
Since errno is not required to be unchanged on
success, in order to correctly detect and possibly recover from errors,
applications should use setvbuf(3) instead of
setbuf ().
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
V2_chap02(3), fopen(3), setvbuf(3)
XBD <stdio.h>
CHANGE HISTORY
First released in Issue 1. Derived from Issue 1 of the SVID.
Issue 6
The prototype for setbuf () is updated for
alignment with the ISO/IEC 9899:1999
(“ISO C99”) standard.
Issue 7
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0546 [397], XSH/TC1-2008/0547 [397], and XSH/TC1-2008/0548 [14] are applied.