setbuf(3)						     Library Functions Manual							 setbuf(3)

NAME

       setbuf, setvbuf, setvbuf_unlocked, setbuffer, setlinebuf - Assign buffering to a stream

LIBRARY

       Standard C Library (libc.so, libc.a)

SYNOPSIS

       #include <stdio.h>

       void setbuf(
	       FILE *stream,
	       char *buffer);

       int setvbuf(
	       FILE *stream,
	       char *buffer,
	       int mode,
	       size_t size);

       int setvbuf_unlocked(
	       FILE *stream,
	       char *buffer,
	       int mode,
	       size_t size);

       void setbuffer(
	       FILE *stream,
	       char *buffer,
	       int size);

       void setlinebuf(
	       FILE *stream);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       setbuf(), setvbuf():  XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies  the  input/output stream.  Points to a character array.  Determines how the stream parameter is buffered.  Specifies the size of
       the buffer to be used.

DESCRIPTION

       The setbuf() function causes the character array pointed to by the buffer parameter to be used instead of an automatically  allocated  buf-
       fer.  Use the setbuf() function after a stream has been opened but before it is read or written.

       If the buffer parameter is a null pointer, input/output is unbuffered.

       A constant, BUFSIZ, defined in the stdio.h header file, tells how large an array is needed:

       char buf[BUFSIZ];

       For  the  setvbuf() function, the mode parameter determines how the stream parameter is buffered: Causes input/output to be fully buffered.
       Causes output to be line buffered.  The buffer is flushed when a new line is written, the buffer is full, or input  is  requested.   Causes
       input/output to be completely unbuffered.

       If  the	buffer	parameter  is not a null pointer, the array that the parameter points to is used for buffering instead of a buffer that is
       automatically allocated.  The size parameter specifies the size of the buffer to be used.  The constant BUFSIZ in the stdio.h  header  file
       is  one	buffer	size.	If input/output is unbuffered, the buffer and size parameters are ignored.  The setbuffer() function, an alternate
       form of the setbuf() function, is used after stream has been opened but before it is read or written.  The character  array  buffer,  whose
       size  is determined by the size parameter, is used instead of an automatically allocated buffer. If the buffer parameter is a null pointer,
       input/output is completely unbuffered.

       The setbuffer() function is not needed under normal circumstances, since the default file I/O buffer size is optimal.

       The setlinebuf() function is used to change stdout or stderr from block buffered or unbuffered to line buffered.  Unlike the  setbuf()  and
       setbuffer() functions, the setlinebuf() function can be used any time the file descriptor is active.

       A  buffer  is  normally obtained from the malloc() function at the time of the first getc() or putc() function on the file, except that the
       standard error stream, stderr, is normally not buffered.

       Output streams directed to terminals are always either line buffered or unbuffered.

       The setvbuf_unlocked() function is functionally identical to the setvbuf() function, except that setvbuf_unlocked() may be safely used only
       within  a scope that is protected by the flockfile() and funlockfile() functions used as a pair.  The caller must ensure that the stream is
       locked before these functions are used.

RETURN VALUES

       The setvbuf() and setvbuf_unlocked() functions return zero when successful.  If they cannot honor the request, or if you  give  an  invalid
       value in the mode argument, they return a nonzero value.

NOTES

       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.

ERRORS

       If the following condition occurs, the setvbuf() function sets errno to the corresponding value.  The file descriptor that underlies stream
       is invalid.

RELATED INFORMATION

       Functions: fopen(3), fread(3), getc(3), getwc(3), malloc(3), putc(3), putwc(3)

       Standards: standards(5) delim off

																	 setbuf(3)