


      SETBUF(3S)                  (UNIX 5.2)                 SETBUF(3S)



      NAME
           setbuf, setvbuf - assign buffering to a stream

      SYNTAX
           #include <stdio.h>

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

           int setvbuf (stream, buf, type, size)
           FILE *stream;
           char *buf;
           int type, size;

      DESCRIPTION
           Setbuf may be used after a stream has been opened but before
           it is read or written.  It causes the array pointed to by
           buf to be used instead of an automatically allocated buffer.
           If buf is the NULL pointer input/output will be completely
           unbuffered.

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

                char buf[BUFSIZ];

           Setvbuf 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 newline 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.  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.

      SEE ALSO
           fopen(3S), getc(3S), malloc(3C), putc(3S), stdio(3S).



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      SETBUF(3S)                  (UNIX 5.2)                 SETBUF(3S)



      DIAGNOSTICS
           If an illegal value for type or size is provided, setvbuf
           returns a non-zero value. Otherwise, the value returned will
           be zero.

      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.














































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