T
tail
A command that displays a user-specifiable number of lines at the end of a text
file.
See also head
tar program
A program that makes portable copies of files for archiving or transfer to another
system. By default, the tar program writes its archive files on the system's
primary magnetic tape unit.
target
In the make utility, an entity to be built from its dependents. An executable
program is a target that is built from one or more object modules. Also called a
target file.
target hierarchy
For building software kits, the directory tree into which a software kit is placed by
the kits command.
task
1. A defined activity; a unit of work to be performed, for example, a user task, a
server task, and a processor task.
2. A process and the procedures that run the process.
TCP (Transmission Control Protocol)
The Internet transport-layer protocol that provides a reliable, full-duplex,
connection-oriented service for applications. TCP uses the IP protocol to transmit
information through the network.
TCP/IP
The two fundamental protocols of the Internet Protocol suite, and an acronym
that is frequently used to refer to the Internet Protocol suite. TCP provides for the
reliable transfer of data, while IP transmits the data through the network in the
form of datagrams.
See also TCP (Transmission Control Protocol), IP (Internet Protocol)
$TERM
An environment variable containing the user's terminal type.
See also environment variable
termcap database
A file containing descriptions of terminal types and capabilities; used by the tset
command and BSD curses library routines to to determine how a given physical
terminal is to be controlled.
See also terminfo database
terminal session
A user's interaction with a computer between the time the user logs in and logs
out.
terminated
The condition of a process that has been pernamently killed. A process that is
terminated is called a terminated job.
See also suspended
terminfo database
A file containing descriptions of terminal types and capabilities; used by the
system and X/Open curses library routines to determine how a given terminal is
to be controlled.
tilde substitution
In the POSIX, Korn, and C shells, use of a tilde ( ~ ) as the first character in a
pathname. By default, the shell interprets the tilde as the pathname of the user's
home directory; for example, if a user whose login name is rolf enters
~/docs/figure_1 as a pathname, the system might expand the entry to be
/usr/users/rolf/docs/figure_1. If the tilde is followed immediately by a user's login
name, the shell interprets the combination as a reference to the named user's
home directory; for example, ~willy represents the path to willy's home directory
when entered by any user on the system.
tool
A command or utility designed to help get a job done; for example make or dbx.
tracepoint
A specific place in a source code program in which the value of a variable is
printed, without pausing the program's execution. Used to test and debug a
program.
See also breakpoint
Transmission Control Protocol
See TCP (Transmission Control Protocol)
transport endpoint
A communication path over which a transport user can exchange data with a
transport provider.
transport provider
A transport protocol that offers transport layer services in a network.
transport services
The support given by the transport layer in a network to the session layer for the
transfer of data between user processes. The two types of services provided are
connection-oriented and connectionless.
transport user
A program needing the services of a transport protocol to send data to or receive
data from another program or point in a network.
trap
1. In data communications, an unprogrammed, hardware-initiated, conditional
jump to a specific address. Similar to an interrupt, but triggered by direct action
of an executing program, rather than by an external event.
2. In programming languages, the process of branching or jumping to a
subroutine that provides the desirable operation when a specific condition
occurs.
3. In the UNIX system, a special statement used to catch signals in a shell script
and transfer control to a handler routine within the script.
trap handler
A system-defined routine used when an abnormal situation arises during a
program's execution.
tree structure
1. The organization of disk directories in most operating systems. Any given
directory can contain files or other directories (called subdirectories), or both. By
extension, any subdirectory can contain subdirectories of its own; when
diagrammed, the resulting structure resembles the branching of a tree.
2. The organization of data in a manner similar to that described for disk
directories. Common tree structures in files are the binary tree, in which each
data element has zero, one, or two elements beneath it (called children); and the
B+ tree, in which each data element can have more than two children, with the
distribution of elements in the tree being balanced so that all of the elements at a
given level have the same or similar numbers of children.
Trojan Horse
A computer program that appears to do something useful, but is also designed to
damage or destroy other files or programs, or the system itself, without the
user's knowledge. An example of a Trojan Horse would be a game program that
secretly erased disk files while the game was being played.
See also virus, worm
trusted host
A computer within a network that permits access without the need to supply
password information.
tty
A shorthand term for a terminal.
