The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### 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.1-2008 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() interface may set errno in defined ways, the value of errno after a call to setbuf() is unspecified.

The following sections are informative.

#### 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() instead of setbuf().

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> Standard I/O Streams, fopen, setvbuf

> 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 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.

End of informative text.

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