setbuffer(3S)           (BSD Compatibility Package)           setbuffer(3S)

NAME
     setbuffer, setlinebuf - assign buffering to a stream

SYNOPSIS
     /usr/ucb/cc [flag ...] file ... -lucb

     #include <stdio.h>

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

     setlinebuf(stream)
     FILE *stream;

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 any line buffered input
     stream. fflush may be used to force the block out early. Normally all
     files are block buffered. A buffer is obtained from malloc upon the
     first getc or putc on the file.

     By default, output to a terminal is line buffered, except for output
     to the standard stream stderr which is unbuffered, and all other
     input/output is fully buffered.

     setbuffer can be used after a stream has been opened but before it is
     read or written. It uses the character array buf whose size is deter-
     mined by the size argument instead of an automatically allocated
     buffer. If buf is the NULL pointer, input/output will be completely
     unbuffered. A manifest constant BUFSIZ, defined in the <stdio.h>
     header file, tells how big an array is needed:

          char buf[BUFSIZ];

     setlinebuf is used to change the buffering on a stream from block buf-
     fered or unbuffered to line buffered. Unlike setbuffer, it can be used
     at any time that the file descriptor is active.

     A file can be changed from unbuffered or line buffered to block buf-
     fered by using freopen. A file can be changed from block buffered or
     line buffered to unbuffered by using freopen followed by setbuffer
     with a buffer argument of NULL.







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setbuffer(3S)           (BSD Compatibility Package)           setbuffer(3S)

NOTE
     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.

SEE ALSO
     malloc(3C), fclose(3S), getc(3S), fopen(3S), fread(3S), printf(3S),
     putc(3S), puts(3S).














































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