setbuf(3S)          (C Programming Language Utilities)           setbuf(3S)


   NAME
         setbuf, setvbuf - assign buffering to a stream

   SYNOPSIS
         #include <stdio.h>

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

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

   DESCRIPTION
         setbuf may be used after a stream [see intro(3)] 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.

         While there is no limitation on the size of the buffer, the constant
         BUFSIZ, defined in the <stdio.h> header file, is typically a good
         buffer size:

               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.  If input/output is
         unbuffered, buf and size are ignored.

         For a further discussion of buffering, see stdio(3S).

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

   DIAGNOSTICS
         If an illegal value for type is provided, setvbuf returns a non-zero
         value. Otherwise, it returns zero.

   NOTES
         A common source of error is allocating buffer space as an
         ``automatic'' variable in a code block, and then failing to close the


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   setbuf(3S)          (C Programming Language Utilities)           setbuf(3S)


         stream in the same block.

         Parts of buf will be used for internal bookkeeping of the stream and,
         therefore, buf will contain less than size bytes when full.  It is
         recommended that the automatically allocated buffer is used when
         using setvbuf.















































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