HP C/iX Library Reference Manual (30026-90004)

304 Chapter5

HP C/iX Library Function Descriptions

setbuf

FILE *fp;

char buffer[BUFSIZ];

fp = fopen(argv[1], "r");

…

setbuf(fp, buffer);

…

This fragment shows the correct order of events. First, the ﬁle is opened, and the buffering

is assigned using setbuf(). From that point on any input taken from fp is buffered

through the array

buffer.

Buffering can be eliminated altogether by specifying the null

pointer in place of the buffer name, as in

setbuf(fp, NULL);

This causes input or output using fp to be completely unbuffered.

The setbuf function is limited to buffer sizes of either BUFSIZ bytes or zero. setbuf()

assumes that the character array pointed to by

buffer

is BUFSIZ bytes. Passing setbuf()

a (non-null) pointer to a smaller array can cause severe problems during operation because

the standard I/O functions might overwrite memory following the end of the buffer.