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setbuf(3s)							    setbuf(3s)

Name
       setbuf, setbuffer, setlinebuf, setvbuf - assign buffering to a stream

Syntax
       #include <stdio.h>

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

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

       void setlinebuf(stream)
       FILE *stream;

       int setvbuf(stream, buf, type, size)
       FILE *stream;
       char *buf;
       int type; 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 new line is
       encountered or input is read from stdin.	 The routine may  be  used  to
       force the block out early.  Normally all files are block buffered.  For
       further information, see A buffer is obtained from upon the first or on
       the  file.   If	the  standard stream stdout refers to a terminal it is
       line buffered.  The standard stream stderr is always unbuffered.

       The routine is used after a stream has been opened  but	before	it  is
       read  or	 written.  The character array buf is used instead of an auto‐
       matically allocated buffer.  If	buf  is	 the  constant	pointer	 NULL,
       input/output will be completely unbuffered.  A manifest constant BUFSIZ
       tells how big an array is needed:
       char buf[BUFSIZ];

       The routine, an alternate form of is  used  after  a  stream  has  been
       opened but before it is read or written.	 The character array buf whose
       size is determined by the size argument is used instead of an automati‐
       cally   allocated  buffer.   If	buf  is	 the  constant	pointer	 NULL,
       input/output will be completely unbuffered.

       The routine is used to change stdout or stderr from block  buffered  or
       unbuffered  to  line  buffered.	 Unlike and it can be used at any time
       that the file descriptor is active.

       The routine may be used after a stream has been opened but before it is
       read  or	 written.  Type determines how stream will be buffered.	 Legal
       values for type, defined in stdio.h are:

	_IOFBF	      causes input/output to be fully buffered.

	_IOLBF	      causes output to be line buffered; the  buffer  will  be
		      flushed  when a new line is written, the buffer is full,
		      or input is requested.

	_IONBF	      causes input/output to be completely unbuffered.

       If buf is not the NULL pointer, the array it points to will be used for
       buffering,  instead  of	an  automatically  allocated buffer.  The size
       specifies the size of the buffer to be used.  The  constant  BUFSIZ  in
       <stdio.h>  is  suggested	 as  a	good  buffer size.  If input/output is
       unbuffered, buf and size are ignored.

       By default, output to  a	 terminal  is  line  buffered  and  all	 other
       input/output is fully buffered.

       A  file	can  be	 changed  from	unbuffered  or	line buffered to block
       buffered by using For further information, see A file  can  be  changed
       from block buffered or line buffered to unbuffered by using followed by
       with a buffer argument of NULL.

Restrictions
       The standard error stream should be line buffered by default.

       The and functions are not portable to non 4.2 BSD versions of UNIX.

See Also
       malloc(3),  fclose(3s),	fopen(3s),  fread(3s),	getc(3s),  printf(3s),
       putc(3s), puts(3s).

								    setbuf(3s)
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