Assign block buffering to a stream
#include <unix.h> void setbuffer( FILE *iop, char *abuf, size_t asize );
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The setbuffer() and setlinebuf() functions assign buffering to a stream. The types of buffering available are:
You can use fflush() to force the block out early. Normally all files are block-buffered. A buffer is obtained from malloc() when you perform the first getc() or putc() on the file. If the standard stream stdout refers to a terminal, it's line-buffered. The standard stream stderr is unbuffered by default.
If you want to use setbuffer(), you must call it after opening the stream, but before doing any reading, writing, or seeking. It uses the character array abuf, whose size is given by asize, instead of an automatically allocated buffer. If abuf is NULL, input and output are completely unbuffered. A manifest constant BUFSIZ, defined in the <stdio.h> header, specifies the default size:
You can use freopen(). to change a stream from unbuffered or line-buffered to block buffered. To change a stream from block-buffered or line-buffered to unbuffered, call freopen(), and then call setvbuf() with a buffer argument of NULL.
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.
fclose(), fflush(), fopen(), fread(), freopen(), getc(), malloc(), printf(), putc(), puts(), setlinebuf(), setvbuf()