Stdio
provides streams for standard input, standard output, and
standard error. These streams correspond to file handles returned
by the GetStandardFileHandles
procedure in the Process
interface.
\index{standard I/O!streams}
INTERFACEThe initialization of these streams depends on the underlying operating system.Stdio ; IMPORT Rd, Wr; VAR stdin: Rd.T; stdout: Wr.T; stderr: Wr.T; bufferedStderr: Wr.T; END Stdio.
If the standard error stream is directed to a terminal, it will be
unbuffered, so that explicit Wr.Flush
calls are unnecessary for
interactive programs. A buffered version of the standard error
stream is also provided, but programs should not use both stderr
and bufferedStderr
.
If the streams are directed to or from random-access files, they will be seekable.
It is possible that stderr
is equal to stdout
. Therefore,
programs that perform seek operations on stdout
should take care
not to destroy output data when writing error messages.