glossary.9 (2010 09)

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glossary(9) glossary(9)
terminal affiliation
The process by which a process group leader establishes an association between itself and a particular
terminal. A terminal becomes affiliated with a process group leader (and subsequently all processes
created by the process group leader, see terminal group) whenever the process group leader executes
(either directly or indirectly) an open (2) or creat (2) system call to open a terminal. Then, if the process
which is executing open (2) or creat (2) is a process group leader, and if that process group leader is not yet
affiliated with a terminal, and if the terminal being opened is not yet affiliated with a process group, the
affiliation is established (however, see open(2) description of
O_NOCTTY).
An affiliated terminal keeps track of its process group affiliation by storing the process group’s process
group ID in an internal structure.
Two benefits are realized by terminal affiliation. First, all signals sent from the terminal are sent to all
processes in the terminal group. Second, all processes in the terminal group can perform I/O to/from the
generic terminal driver
/dev/tty, which automatically selects the affiliated terminal.
Terminal affiliation is broken with a terminal group when the process group leader terminates, after
which the hangup signal is sent to all processes remaining in the process group. Also, if a process (which
is not a process group leader) in the terminal group becomes a process group leader via the setpgrp (2)
system call, its terminal affiliation is broken.
See process group, process group leader, terminal group, and setpgrp (2).
terminal device
See terminal.
text file
A file that contains characters organized into one or more lines. The lines cannot contain NUL charac-
ters, and none can exceed
LINE_MAX bytes in length including the terminating newline character.
Although neither the kernel nor the C language implementation distinguishes between text files and
binary files (see ANSI C Standard X3-159-19xx), many utilities behave predictably only when operating
on text files.
tty
Originally, an abbreviation for teletypewriter; now, generally, a terminal.
upshifting
The conversion of a lowercase character to its uppercase representation.
user ID
Each system user is identified by an integer known as a user ID, which is in the range of zero to
UID_MAX, inclusive. Depending on how the user is identified with a process, a user ID value is referred
to as a real user ID,aneffective user ID,orasaved user ID.
UTC
See Epoch.
utility
An executable file, which might contain executable object code (that is, a program), or a list of com-
mands to execute in a given order (that is, a shell script). You can write your own utilities, either as
executable programs or shell scripts (which are written in the shell programming language).
volume number
Part of an address used for devices. A number whose meaning is software- and device-dependent, but
which is often used to specify a particular volume on a multivolume disk drive. See the System Adminis-
trator manuals supplied with your system for details.
whitespace
One or more characters which, when displayed, cause a movement of the cursor or print head, but do not
result in the display of any visible graphic. The whitespace characters in the ASCII code set are space,
tab, newline, form feed, carriage return, and vertical tab. A particular command or routine might inter-
pret some, but not necessarily all, whitespace characters as delimiters for fields, words, or command
options.
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