putchar.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th PUTCHAR III 5/10/73
.sh NAME
putchar, flush \*- write character
.sh SYNOPSIS
.ft B
putchar(ch)
.s3
flush( )
.ft R
.sh DESCRIPTION
.it Putchar
writes out its argument and returns it unchanged.
Only the low-order byte is written, and only if it is non-null.
Unless other arrangements have been made,
.it putchar
writes in
unbuffered fashion on the standard output file.
.s3
Associated with this routine is an external variable
.it fout
which has the
structure of a buffer discussed under putc (III).
If the file descriptor part of this structure (first word)
is greater than 2, output via
.it putchar
is buffered.
To achieve buffered output one may say, for example,
.s3
.nf
	fout = dup(1);		or
	fout = creat(...);
.s3
.fi
In such a case
.it flush
must be called
before the program terminates in order to flush out
the buffered output.
.it Flush
may be called at any time.
.sh "SEE ALSO"
putc (III)
.sh BUGS
The
.it fout
notion is kludgy.