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Test Your Knowledge in Computers #582
Difficulty: Medium
A buffered input or output stream is one in which data that is read or written is actually stored in memory in a buffer until such a time as the buffer is flushed and the accumulated data is passed to or from the actual file.
True or False?
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tty(4) [debian man page]

TTY(4)							     Linux Programmer's Manual							    TTY(4)

NAME
tty - controlling terminal DESCRIPTION
The file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and owner.group root.tty. It is a syn- onym for the controlling terminal of a process, if any. In addition to the ioctl(2) requests supported by the device that tty refers to, the ioctl(2) request TIOCNOTTY is supported. TIOCNOTTY Detach the calling process from its controlling terminal. If the process is the session leader, then SIGHUP and SIGCONT signals are sent to the foreground process group and all processes in the current session lose their controlling tty. This ioctl(2) call only works on file descriptors connected to /dev/tty. It is used by daemon processes when they are invoked by a user at a terminal. The process attempts to open /dev/tty. If the open succeeds, it detaches itself from the terminal by using TIOCNOTTY, while if the open fails, it is obviously not attached to a terminal and does not need to detach itself. FILES
/dev/tty SEE ALSO
chown(1), mknod(1), ioctl(2), termios(3), console(4), tty_ioctl(4), ttyS(4), agetty(8), mingetty(8) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2003-04-07 TTY(4)

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TCGETPGRP(3)						     Linux Programmer's Manual						      TCGETPGRP(3)

NAME
tcgetpgrp, tcsetpgrp - get and set terminal foreground process group SYNOPSIS
#include <unistd.h> pid_t tcgetpgrp(int fd); int tcsetpgrp(int fd, pid_t pgrp); DESCRIPTION
The function tcgetpgrp() returns the process group ID of the foreground process group on the terminal associated to fd, which must be the controlling terminal of the calling process. The function tcsetpgrp() makes the process group with process group ID pgrp the foreground process group on the terminal associated to fd, which must be the controlling terminal of the calling process, and still be associated with its session. Moreover, pgrp must be a (nonempty) process group belonging to the same session as the calling process. If tcsetpgrp() is called by a member of a background process group in its session, and the calling process is not blocking or ignoring SIGTTOU, a SIGTTOU signal is sent to all members of this background process group. RETURN VALUE
When fd refers to the controlling terminal of the calling process, the function tcgetpgrp() will return the foreground process group ID of that terminal if there is one, and some value larger than 1 that is not presently a process group ID otherwise. When fd does not refer to the controlling terminal of the calling process, -1 is returned, and errno is set appropriately. When successful, tcsetpgrp() returns 0. Otherwise, it returns -1, and errno is set appropriately. ERRORS
EBADF fd is not a valid file descriptor. EINVAL pgrp has an unsupported value. ENOTTY The calling process does not have a controlling terminal, or it has one but it is not described by fd, or, for tcsetpgrp(), this controlling terminal is no longer associated with the session of the calling process. EPERM pgrp has a supported value, but is not the process group ID of a process in the same session as the calling process. CONFORMING TO
POSIX.1-2001. NOTES
These functions are implemented via the TIOCGPGRP and TIOCSPGRP ioctls. History The ioctls appeared in 4.2BSD. The functions are POSIX inventions. SEE ALSO
setpgid(2), setsid(2), credentials(7) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2003-01-28 TCGETPGRP(3)

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