Sams Teach Yourself C++ in 21 Days

• cin(pronounced “see-in”) handles input from the standard input, the keyboard.


• cout(pronounced “see-out”) handles output to the standard output, the console
  screen.


• cerr(pronounced “see-err”) handles unbuffered output to the standard error
  device, the console screen. Because this is unbuffered, everything sent to cerris
  written to the standard error device immediately, without waiting for the buffer to
  fill or for a flush command to be received.


• clog(pronounced “see-log”) handles buffered error messages that are output to the
  standard error device, the console screen. It is common for this to be “redirected”
  to a log file, as described in the following section.

Redirection of the Standard Streams ..................................................................

Each of the standard devices, input, output, and error, can be redirected to other devices.

The standard error stream (cerr) is often redirected to a file, and standard input (cin)

and output (cout) can be piped to files using operating system commands.

Redirecting refers to sending output (or input) to a place different than the default.

Redirection is more a function of the operating system than of the iostreamlibraries.

C++ just provides access to the four standard devices; it is up to the user to redirect the

devices to whatever alternatives are needed.

The redirection operators for DOS, the Windows command prompt, and Unix are (<)

redirect input and (>) redirect output. Unix provides more advanced redirection capabili-

ties than DOS or the standard Windows command prompt; however, the general idea is

the same: Take the output intended for the console screen and write it to a file, or pipe it

into another program. Alternatively, the input for a program can be extracted from a file

rather than from the keyboard.

598 Day 17

The iostreamclass library is added automatically to your program by the

compiler. All you need to do to use these functions is to put the appropriate

includestatement at the top of your program listing:

#include <iostream>

This is something you have been doing in your programs already.

NOTE

NOTE Piping refers to using the output of one program as the input of another.