P
package
For the DIGITAL UNIX operating system loader, a collection of object entities that
share a common name space. Symbol names are unique within a package.
Symbols from different packages may bear identical symbol names because they
are distinguished by their package names.
page
A fixed-size unit of physical memory.
PALcode (Privileged Architecture Library)
A set of subroutines that are specific to a particular Alpha operating system
implementation. These subroutines provide operating-system primitives for
context switching interrupts, exceptions, and memory management.
parent directory
The directory in which another directory resides. The directory that is contained in
the parent is called a subdirectory.
parent process
A process that has created other processes, called its children. In the UNIX
system, every command that is not a shell built-in command creates a child
process.
See also fork
parser
A program or program fragment for interpreting input and determining how to
act upon it. The yacc program assists in the creation of parsers.
See also lexical analyzer
parsing order
The sequence in which a program interprets information that is input to it. For
example, a program using left-to-right parsing order interprets input reading
"create a number; write the number" so that the number created by the first step
is written. A program with right-to-left parsing order interprets the same input to
mean that the program is to write a number that it created in some previous step
and then to create a new number.
partition
A physical portion of a disk. Disks are divided into partitions that are then
assigned to hold various file systems. For example, the root file system is usually
on the first partition, named a. The /usr file system is on a different partition,
often the g partition. The use of partitions provides flexibility and control of disk
usage, but it is restricted in that it denies unlimited use of all the available space
on a given disk for a given file.
passive user
In an XTI transport connection, the transport user that did not initiate the
connection.
See also client process, active user, XTI (X/Open Transport Interface)
passwd
1. The command by which users change their login password.
2. The UNIX file in which user passwords and associated information are stored;
the file's pathname is /etc/passwd.
$PATH
An environment variable containing the user's search path for commands.
Directory names in the $PATH variable are separated with colons.
See also $path
$path
A process variable containing the user's search path for commands. Directory
names in the $path variable are separated with spaces.
See also $PATH
path
An ordered list of the directories in which the shell searches for the executable
files named by commands that are not entered with a pathname and are not shell
built-in commands.
See also $PATH, $path
pathname
The name of a file, concatenated onto a list of the directories through which
access to that file is achieved; hence, the complete name of the file. Absolute
pathnames begin at the root directory and are written with an initial slash (for
example, /usr/users/rolf/myfile.txt). Relative pathnames begin at the user's
working directory and are written without the initial slash (for example,
rolf/myfile.txt).
pathname qualifier
See variable modifier
pattern matching
The process of comparing input information (usually text) against a specified set
of symbols (usually regular expressions) to find correspondences.
See also regular expression
pattern space
In the sed editor, the range of lines currently being edited; the pattern space is
selected by an address or pair of addresses.
permission code
See permissions
permission field
See permissions
permissions
The constraints a user places on a file to control what other users or groups may
read, write, or execute the file. There are three sets of permissions: those applied
to the user, those applied to the user's group, and those applied to everyone else,
called "other."
pid, PID
See process ID
pipe
The construct that couples the output of one program directory to the input of
another. Pipes are created by the use of a vertical bar ( | ) between commands on
the command line. For example:
% nroff inputfile -ms | lpr
This pipeline processes the input file (with the nroff command) and sends the
processed file directly to the printer (the lpr command).
See also pipeline
pipeline
A series of commands connected by pipes. The process of coupling the output of
one command directly to the input of another with a pipe is called pipelining or
piping.
piping
See pipeline
pixel (picture element)
The smallest element of a display in a graphics application. On a video screen,
pixels are the dots that produce the visual image. The number of pixels usually
determines the resolution of the image; the more pixels, the better the
resolution.
Point-to-Point Protocol
See PPP (Point-to-Point Protocol)
pointer
A symbol that specifies position by reflecting the motion of the mouse. The
pointer can change shape to indicate the function of the area in which the pointer
is position.
See also cursor
POSIX (Portable Operating System Interface for Computer Environments)
A collection of standards proposed by the POSIX working groups of the Institute
of Electrical and Electronics Engineers (IEEE). POSIX standards define system
interfaces to support the source portability of applications.
See also SVID (System V Interface Definition)
POSIX shell
The shell that conforms to the POSIX standard. The POSIX shell (sh) is a subset of
the Korn shell.
See also Korn shell, shell
PostScript
The registered trademark for a language developed by Adobe Systems, Inc., for
specifying the formatting of typeset documents or displays. An encapsulated
PostScript file is a file that follows a standard for embedding PostScript files into
other PostScript files.
PPP (Point-to-Point Protocol)
A transmission line protocol that encapsulates and transfers IP datagrams over
asynchronous serial lines. PPP is more efficient than SLIP.
See also SLIP (Serial Line Internet Protocol)
predefined variable
A shell variable defined and maintained by the C shell.
preprocessor
A program that translates some portion of its information in a file into a form
understandable to another program. For example, the tbl program is a
preprocessor for the nroff text formatter.
printcap database
A file (/etc/printcap) containing descriptions of all the printers known to the
system.
process ID
A unique number assigned to a process that is running.
process identification
See process ID
process table
A kernel data structure that contains relevant information about all processes in
the system.
process variable
A symbol containing information that can be used by the current process only.
Process variables are not automatically propagated to child processes.
See also environment variable
profile data
Information about how a program is spending its execution time.
See also profiling
profiling
The monitoring of how system resources are utilized in a given program. Profiling
helps programmers improve the efficiency of their program code. Different
versions of the UNIX operating system provide different profiling utilities that
work in different ways.
pseudodevice
A device that consists of a software simulation, rather than hardware; for
example, a pty (pseudo-tty) device.
pseudoterminal
A special file that effectively functions as a keyboard and display device.
See also pseudodevice
pseudo-tty
See pseudoterminal
pty
See pseudoterminal
pwd
The command that causes the system to display the absolute pathname of the
user's working directory.
See also working directory
