glossary(9)

. (dot)

A special file name that refers to the current directory. It can be used alone or at the beginning of a directory path name. See also path name resolution. The dot also functions as a special command in the POSIX, Bourne, and Korn shells, and has special meaning in text editors and formatters, in parsing regular expressions and in designating file names.

.. (dot-dot)

A special file name that refers to the parent directory. If it begins a path name, dot-dot refers to the parent of the current directory. If it occurs in a path name, dot-dot refers to the parent directory of the directory preceding dot-dot in the path name string. As a special case, dot-dot refers to the current directory in any directory that has no parent (most often, the root directory). See also path name resolution.

.o (dot-oh)

The suffix customarily given to a relocatable object file. The term dot-oh file is sometimes used to refer to a relocatable object file. The format of such files is sometimes called dot-oh format. See a.out(4).

a.out

The name customarily given to an executable object code file on HP-UX. The format is machine-dependent, and is described in a.out(4) for each implementation. Object code that is not yet linked has the same format, but is referred to as a .o (dot-oh) file. a.out is also the default output file name used by the linker, ld(1).

absolute path name

A path name beginning with a slash (/). It indicates that the file's location is given relative to the root directory (/), and that the search begins there.

access

The process of obtaining data from or placing data in storage, or the right to use system resources. Accessibility is governed by three process characteristics: the effective user ID, the effective group ID, and the group access list. The access(2) system call determines accessibility of a file according to the bit pattern contained in its amode parameter, which is constructed to read, write, execute or check the existence of a file. The access(2) system call uses the real user ID instead of the effective user ID and the real group ID instead of the effective group ID.

access groups

The group access list is a set of supplementary group IDs used in determining resource accessibility. Access checks are performed as described below in file access permissions.

access mode

An access mode is a form of access permitted to a file. Each implementation provides separate read, write, and execute/search access modes.

address

A number used in information storage or retrieval to specify and identify memory location. An address is used to mark, direct, indicate destination, instruct or otherwise communicate with computer elements.

In mail, address is a data structure whose format can be recognized by all elements involved in transmitting information. On a local system, this might be as simple as the user's login name, while in a networked system, address specifies the location of the resource to the network software.

In a text editor (such as vi, ex, ed, or sed), an address locates the line in a file on which a given instruction is intended.

For adb, the address specifies at what assembly-language instruction to execute a given command.

In disk utilities such as fsdb, address might refer to a raw or block special file, the inode number, volume header, or other file attribute.

In the context of peripheral devices, address refers to a set of values that specify the location of an I/O device to the computer. The exact details of the formation of an address differ between systems.

address space

The range of memory locations to which a process can refer.

affiliation

See terminal affiliation.

agile addressing

An addressing scheme where an address or path to a logical unit that is independent of the physical path. See intro(7) for more information.

appropriate privileges

Each implementation provides a means of associating privileges with a process for function calls and function call options requiring special privileges. In the HP-UX system, appropriate privileges refers either to superuser status or to a privilege associated with privilege groups (see setprivgrp(1M)).

archive

A file comprised of the contents of other files, such as a group of object files (that is, .o) used by the linker, ld(1)). An archive file is created and maintained by ar(1) or similar programs, such as tar(1) or cpio(1). An archive is often called a library.

ASCII

An acronym for American Standard Code for Information Interchange. ASCII is the traditional System V coded character set and defines 128 characters, including both control characters and graphic characters, each of which is represented by 7-bit binary values ranging from 0 through 127 decimal.

background process group

Any process group that is a member of a session which has established a connection with a controlling terminal that is not in the foreground process group.

backup

The process of making a copy of all or part of the file system in order to preserve it, in case a system crash occurs (usually due to a power failure, hardware error, etc.). This is a highly recommended practice.

block

block special file

A special file associated with a mass storage device (such as a hard disk or tape cartridge drive) that transfers data in multiple-byte blocks, rather than by series of individual bytes (see character special file). Block special files can be mounted. A block special file provides access to the device where hardware characteristics of the device are not visible.

boot, boot-up

The process of loading, initializing, and running an operating system.

boot area

A portion of a mass storage medium on which the volume header and a "bootstrap" program used in booting the operating system reside. The boot area is reserved exclusively for use by HP-UX.

boot ROM

A program residing in ROM (Read-Only Memory) that executes each time the computer is powered up and is designed to bring the computer to a desired state by means of its own action. The first few instructions of a bootstrap program are sufficient to bring the remainder of the program into the computer from an input device and initiate functions necessary for computation. The function of the boot ROM is to run tests on the computer's hardware, find all devices accessible through the computer, and then load either a specified operating system or the first operating system found according to a specific search algorithm.

bus address

A number which makes up part of the address HP-UX uses to locate a particular device. The bus address is determined by a switch setting on a peripheral device which allows the computer to distinguish between two devices connected to the same interface. A bus address is sometimes called a "device address".

character

An element used for the organization, control, or representation of text. Characters include graphic characters and control characters.

character set

A set of characters used to communicate in a native or computer language.

character special file

A special file associated with I/O devices that transfer data byte-by-byte. Other byte-mode I/O devices include printers, nine-track magnetic tape drives, and disk drives when accessed in "raw" mode (see raw disk). A character special file has no predefined structure.

child process

A new process created by a pre-existing process via the fork(2) system call. The new process is thereafter known to the pre-existing process as its child process. The pre-existing process is the parent process of the new process. See parent process and fork.

clock tick

A rate used within the system for scheduling and accounting. It consists of the number of intervals per second as defined by CLK_TCK that is used to express the value in type clock_t. CLK_TCK was previously known as the defined constant HZ.

coded character set

A set of unambiguous rules that establishes a character set and the one-to-one relationship between each character of the set and its corresponding bit representation. ASCII is a coded character set.

collating element

The smallest entity used in collation to determine the logical ordering of strings (that is, the collation sequence). To accommodate native languages, a collating element consists of either a single character, or two or more characters collating as a single entity. The current value of the LANG environment variable determines the current set of collating elements.

collation

The logical ordering of strings in a predefined sequence according to rules established by precedence. These rules identify a collation sequence among the collating elements and also govern the ordering of strings consisting of multiple collating elements, to accommodate native languages.

collation sequence

The ordering sequence applied to collating elements when they are sorted. To accommodate native languages, collation sequence can be thought of as the relative order of collating elements as set by the current value of the LANG environment variable. Characters can be omitted from the collation sequence, or two or more collating elements can be given the same relative order (see string(3C)).

command

A directive to perform a particular task. HP-UX commands are executed through a command interpreter called a shell. HP-UX supports several shells, including the POSIX shell ( sh-posix(1)), the C shell ( csh(1)), and the Korn shell ( ksh(1)). See sh(1) for more information about supported shells. Most commands are carried out by an executable file, called a utility, which might take the form of a stand-alone unit of executable object code (a program) or a file containing a list of other programs to execute in a given order (a shell script). Scripts can contain references to other scripts, as well as to object-code programs. A typical command consists of the utility name followed by arguments that are passed to the utility. For example, in the command, ls mydirectory, ls is the utility name and mydirectory is an argument passed to the ls utility.

command interpreter

A program which reads lines of text from standard input (typed at the keyboard or read from a file), and interprets them as requests to execute other programs. A command interpreter for HP-UX is called a shell. See sh(1) and related manual entries.

Command Set 1980

See CS/80.

composite graphic symbol

A graphic symbol consisting of a combination of two or more other graphic symbols in a single character position, such as a diacritical mark and a basic letter.

control character

A character other than a graphic character that affects the recording, processing, transmission, or interpretation of text. In the ASCII character set, control characters are those in the range 0 through 31, and 127. Control characters can be generated by holding down the control key (which may be labeled CTRL, CONTROL, or CNTL depending on your terminal), and pressing a character key (as you would use SHIFT). These two-key sequences are often written as, for example, Control-D, Ctrl-D, or ^D, where ^ stands for the control key.

controlling process

The session leader that establishes the connection to the controlling terminal. Should the terminal subsequently cease to be a controlling terminal for this session, the session leader ceases to be the controlling process.

controlling terminal

A terminal that is associated with a session. Each session can have at most one controlling terminal associated with it and a controlling terminal is associated with exactly one session. Certain input sequences from the controlling terminal cause signals to be sent to all processes in the foreground process group associated with the controlling terminal.

Coordinated Universal Time (UTC)

See Epoch.

CS/80, CS-80

A family of mass storage devices that communicate with the controlling computer by means of a series of commands and data transfer protocol referred to as the CS/80 (Command Set 1980) command set. This command set was implemented in order to provide better forward/backward compatibility between models and generations of mass storage devices as technological advances develop. Some mass storage devices support only a subset of the full CS/80 command set, and are usually referred to as SS/80 (Subset 1980) devices.

crash

The unexpected shutdown of a program or system. If the operating system crashes, this is a "system crash", and requires the system to be rebooted.

current directory

See working directory.

current working directory

See working directory.

daemon

A process which runs in the background, and which is usually immune to termination instructions from a terminal. Its purpose is to perform various scheduling, clean-up, and maintenance jobs. lpsched(1M) is an example of a daemon. It exists to perform these functions for line printer jobs queued by lp(1). An example of a permanent daemon (that is, one that should never die) is cron(1M).

data encryption

A method for encoding information in order to protect sensitive or proprietary data. For example, HP-UX automatically encrypts all users' passwords. The encryption method used by HP-UX converts ASCII text into a base-64 representation using the alphabet ., /, 0-9, A-Z, a-z. See passwd(4) for the numerical equivalents associated with this alphabet.

default search path

The sequence of directory prefixes that sh(1), time(1), and other HP-UX commands apply in searching for a file known by an relative path name (that is, a path name not beginning with a slash (/)). It is defined by the environment variable PATH (see environ(5)). login(1) sets PATH equal to :/usr/bin, which means that your working directory is the first directory searched, followed by /usr/bin. The search path can be redefined by modifying the value of PATH. This is usually done in /etc/profile, and/or in the .profile file found in the home directory.

defunct process

See zombie process.

delta

A term used in the Source Code Control System (SCCS) to describe a unit of one or more textual changes to an SCCS file. Each time an SCCS file is edited, changes made to the file are stored separately as a delta. The get(1) command is then used to specify which deltas are to be applied to or excluded from the SCCS file, thus yielding a particular version of the file. Contrast this with the vi or ed editor, which incorporates changes into the file immediately, eliminating any possibility of obtaining a previous version of that file. A similar capability is provided by RCS files (see rcsintro(5)).

demon

Improper spelling of the UNIX word daemon.

device

A computer peripheral or an object that appears to an application as such.

device address

See bus address.

device file

See special file.

directory

A file that provides the mapping between the names of files and their contents, and is manipulated by the operating system alone. For every file name contained in a directory, that directory contains a pointer to the file's inode; The pointer is called a link. A file can have several links appearing anywhere on the same file system. Each user is free to create as many directories as needed (using mkdir(1)), provided that the parent directory of the new directory gives the permission to do so. Once a directory has been created, it is ready to contain ordinary files and other directories. An HP-UX directory is named and behaves exactly like an ordinary file, with one exception: no user (including the superuser) is allowed to write data on the directory itself; this privilege is reserved for the HP-UX operating system.

By convention, a directory contains at least two links, . and .., referred to as dot and dot-dot respectively. . refers to the directory itself and .. refers to its parent directory. A directory containing only . and .. is considered empty.

dot

See . (dot).

dot-dot

See .. (dot-dot).

dot-oh

See .o (dot-oh).

dot-oh file

See .o (dot-oh).

dot-oh format

See .o (dot-oh).

downshifting

The conversion of an uppercase character to its lowercase representation.

dynamic loader

A routine invoked at process startup time that loads shared libraries into a process's address space. The dynamic loader also resolves symbolic references between a program and the shared libraries, and initializes the shared libraries' linkage tables. See dld.sl(5) (PA-RISC systems) or dld.so(5) (Itanium®-based systems) for details.

effective group ID

Every process has an effective group ID that is used to determine file access permissions. A process's effective group ID is determined by the file (command) that process is executing. If that file's set-group-ID bit is set (located in the mode of the file, see mode), the process's effective group ID is set equal to the file's group ID. This makes the process appear to belong to the file's group, perhaps enabling the process to access files that must be accessed in order for the program to execute successfully. If the file's set-group-ID bit is not set, the process's effective group ID is inherited from the process's parent. The setting of the process's effective group ID lasts only as long as the program is being executed, after which the process's effective group ID is set equal to its real group ID. See group, real group ID, and set-group-ID bit.

effective user ID

A process has an effective user ID that is used to determine file access permissions (and other permissions with respect to system calls, if the effective user ID is 0, which means superuser). A process's effective user ID is determined by the file (command) that process is executing. If that file's set-user-ID bit is set (located in the mode of the file, see mode), the process's effective user ID is set equal to the file's user ID. This makes the process appear to be the file's owner, enabling the process to access files which must be accessed in order for the program to execute successfully. (Many HP-UX commands which are owned by root, such as mkdir and mail, have their set-user-ID bit set so other users can execute these commands.) If the file's set-user-ID bit is not set, the process's effective user ID is inherited from that process's parent. See real user ID and set-user-ID bit.

end-of-file (EOF)

environment

The set of defined shell variables (such as EXINIT, HOME, PATH, SHELL, TERM, and others) that define the conditions under which user commands run. These conditions can include user terminal characteristics, home directory, and default search path. Each shell variable setting in the current process is passed on to all child processes that are created, provided that each shell variable setting has been exported via the export command (see sh(1)). Unexported shell variable settings are meaningful only to the current process, and any child processes created get the default settings of certain shell variables by executing /etc/profile, $HOME/.profile, or $HOME/.login.

EOF

See end-of-file.

Epoch

The time period beginning at 0 hours, 0 minutes, 0 seconds, Coordinated Universal Time (UTC ) on January 1, 1970. Increments quantify the amount of time elapsed from the Epoch to the referenced time.

Leap seconds, which occur at irregular intervals, are not reflected in the count of seconds between the Epoch and the referenced time. (Fourteen leap seconds occurred in the years 1970 through 1988.)

FIFO special file

A type of file. Data written to a FIFO is read on a first-in-first-out basis. Other characteristics are described in open(2), read(2), write(2) and lseek(2).

file

A stream of bytes that can be written to and/or read from. A file has certain attributes, including permissions and type. File types include regular file, character special file, block special file, FIFO special file, network special file, directory, and symbolic link. Every file must have a file name that enables the user (and many of the HP-UX commands) to refer to the contents of the file. The system imposes no particular structure on the contents of a file, although some programs do. Files can be accessed serially or randomly (indexed by byte offset). The interpretation of file contents and structure is up to the programs that access the file.

file access mode

A characteristic of an open file description that determines whether the described file is open for reading, writing, or both. (See open(2).)

file access permissions

Every file in the file hierarchy has a set of access permissions. These permissions are used in determining whether a process can perform a requested operation on the file (such as opening a file for writing). Access permissions are established when a file is created via the open(2) or creat(2) system calls, and can be changed subsequently through the chmod(2) call. These permissions are read by stat(2) or fstat(2).

File access controls whether a file can be read, written, or executed. Directory files use the execute permission to control whether or not the directory can be searched.

File access permissions are interpreted by the system as they apply to three different classes of users: the owner of the file, the users in the file's group, and anyone else ("other"). Every file has an independent set of access permissions for each of these classes. When an access check is made, the system decides if permission should be granted by checking the access information applicable to the caller.

Read, write, and execute/search permissions on a file are granted to a process if any of the following conditions are met:

Otherwise, the corresponding permissions are denied.

file descriptor

A small unique, per-process, nonnegative integer identifier that is used to refer to a file opened for reading and/or writing. Each file descriptor refers to exactly one open file description.

A file descriptor is obtained through system calls such as creat(2), fcntl(2), open(2), pipe(2), or dup(2). The file descriptor is used as an argument by calls such as read(2), write(2), ioctl(2), and close(2).

The value of a file descriptor has a range from 0 to one less than the system-defined maximum. The system-defined maximum is the value NOFILE in <sys/param.h>.

file group class

A process is in the file group class of a file if the process is not the file owner class and if the effective group ID or one of the supplementary group IDs of the process matches the group ID associated with the file.

file hierarchy

The collection of one or more file systems available on a system. All files in these file systems are organized in a single hierarchical structure in which all of the nonterminal nodes are directories. Because multiple links can refer to the same file, the directory is properly described as a directed graph.

file name

A string of up to 14 bytes (or 255 bytes on file systems that support long file names) used to refer to an ordinary file, special file, or directory. The byte values NUL (null) and slash (/) cannot be used as characters in a file name. Note that it is generally unwise to use *, ?, ,, [, or ] as part of file names because the shell attaches special meaning to these characters (see sh(1), csh(1), or ksh(1)). Avoid beginning a file name with -, +, or =, because to some programs, these characters signify that a command argument follows. A file name is sometimes called a path name component. Although permitted, it is inadvisable to use characters that do not have a printable graphic on the hardware you commonly use, or that are likely to confuse your terminal.

file name portability

File names should be constructed from the portable file name character set because the use of other characters can be confusing or ambiguous in certain contexts.

file offset

The file offset specifies the position in the file where the next I/O operation begins. Each open file description associated with either a regular file or special file has a file offset. There is no file offset specified for a pipe or FIFO.

file other class

A process is in the file other class if the process is not in the file owner class or file group class.

file owner class

A process is in the file owner class if the effective user ID of the process matches the user ID of the file.

file permission bits

See permission bits.

file pointer

A data element obtained through any of the fopen(3S) standard I/O library routines that "points to" (refers to) a file opened for reading and/or writing, and which keeps track of where the next I/O operation will take place in the file (in the form of a byte offset relative to the beginning of the file). After obtaining the file pointer, it must thereafter be used to refer to the open file when using any of the standard I/O library routines. (See stdio(3S) for a list of these routines.)

file serial number

A file-system-unique identifier for a given file, also known as the file's inode number. Each file serial number identifies exactly one inode. File serial numbers are not necessarily unique across file systems in the file hierarchy.

file status flags

Part of an open file description. These flags can be used to modify the behavior of system calls that access the file described by the open file description.

file system

A collection of files and supporting data structures residing on a mass storage volume. A file system provides a name space for file serial numbers referring to those files. Refer to the System Administrator manuals supplied with your system for details concerning file system implementation and maintenance.

file times update

Each file has three associated time values that are updated when file data is accessed or modified, or when the file status is changed. These values are returned in the file characteristics structure, as described in <sys/stat.h>. For each function in HP-UX that reads or writes file data or changes the file status, the appropriate time-related files are noted as "marked-for-update". When an update point occurs, any marked fields are set to the current time and the update marks are cleared. One such update point occurs when the file is no longer open for any process. Updates are not performed for files on read-only file systems.

filter

A command that reads data from the standard input, performs a transformation on the data, and writes it to the standard output.

foreground process group

Each session that has established a connection with a controlling terminal has exactly one process group of the session as a foreground process group of that controlling terminal. The foreground process group has certain privileges when accessing its controlling terminal that are denied to background process groups. See read(2) and write(2).

foreground process group ID

The process group ID of the foreground process group.

fork

An HP-UX system call (see fork(2)), which, when invoked by an existing process, causes a new process to be created. The new process is called the child process; the existing process is called the parent process. The child process is created by making an exact copy of the parent process. The parent and child processes are able to identify themselves by the value returned by their corresponding fork call (see fork(2) for details).

graphic character

A character other than a control character that has a visual representation when hand-written, printed, or displayed.

group

See group ID.

group ID

Associates zero or more users who must all be permitted to access the same set of files. The members of a group are defined in the files /etc/passwd and /etc/logingroup (if it exists) via a numerical group ID that must be between zero and UID_MAX, inclusive. Users with identical group IDs are members of the same group. An ASCII group name is associated with each group ID in the file /etc/group. A group ID is also associated with every file in the file hierarchy, and the mode of each file contains a set of permission bits that apply only to this group. Thus, if you belong to a group that is associated with a file, and if the appropriate permissions are granted to your group in the file's mode, you can access the file. When the identity of a group is associated with a process, a group ID value is referred to as a real group ID, an effective group ID, a supplementary group ID, or a saved group ID. See also privileged group and set-group-ID bit.

group access list

A set of supplementary group IDs used in determining resource accessibility. Access checks are performed as described in file access permissions.

hardware path

A numeric string associated to a system component (bus, card, attached I/O device, and so on) and providing information related to the component location.

hierarchical directory

A directory (or file system) structure in which each directory can contain other directories as well as files.

home directory

The directory name given by the value of the environment variable HOME. When you first log in, login(1) automatically sets HOME to your login directory. You can change its value at any time. This is usually done in the .profile file contained in your login directory. Setting HOME does not affect your login directory; it simply gives you a convenient way of referring to what is probably your most commonly used directory.

host name

A string of bytes that uniquely identifies the system in the network. The host name for your system can be viewed and/or set with the hostname(1) command. More information can be found in the hostname(5) manpage. See also node name.

image

The current state of your computer (or your portion of the computer, on a multiuser system) during the execution of a command. Often thought of as a "snapshot" of the state of the machine at any particular moment during execution.

init

A system process that performs initialization, is the ancestor of every other process in the system, and is used to start login processes. init usually has a process ID of 1. See init(1M).

interleave factor

A number that determines the order in which sectors on a mass storage medium are accessed. It can be optimized to make data acquisition more efficient.

inode

An inode is a structure that describes a file and is identified in the system by a file serial number. Every file or directory has associated with it an inode. Permissions that specify who can access the file and how are kept in a 9-bit field that is part of the inode. The inode also contains the file size, the user and group ID of the file, the number of links, and pointers to the disk blocks where the file's contents can be found. Each connection between an inode and its entry in one or more directories is called a link.

inode number

See file serial number.

Internal Terminal Emulator (ITE)

The "device driver" code contained in the HP-UX kernel that is associated with the computer's built-in keyboard and display or with a particular keyboard and display connected to the computer, depending on the Series and Model of system processor. See system console and the System Administrator manuals supplied with your system for details.

internationalization

The concept of providing software with the ability to support the native language, local customs, and coded character set of the user.

interrupt signal

The signal sent by SIGINT (see signal(2)). This signal generally terminates whatever program you are running. The key which sends this signal can be redefined with ioctl(2) or stty(1) (see termio(7)). It is often the ASCII DEL (rubout) character (the DEL key) or the BREAK key. Ctrl-C is often used instead.

intrinsic

See system call.

I/O redirection

A mechanism provided by the HP-UX shell for changing the source of data for standard input and/or the destination of data for standard output and standard error. See sh(1).

ITE

See Internal Terminal Emulator.

job control

Job control allows users to selectively stop (suspend) execution of processes and continue (resume) their execution at a later time.

The user employs this facility via the interactive interface jointly supplied by the system terminal driver and certain shells (see sh(1)). The terminal driver recognizes a user-defined "suspend character", which causes the current foreground process group to stop and the user's job control shell to resume. The job control shell provides commands that continue stopped process groups in either the foreground or background. The terminal driver also stops a background process group when any member of the background process group attempts to read from or write to the user's terminal. This allows the user to finish or suspend the foreground process group without interruption and continue the stopped background process group at a more convenient time.

See stty(1), sh(1), and related shell entries for usage and installation details, and the shell entries plus signal(2) and termio(7) for implementation details.

kernel

The HP-UX operating system. The kernel is the executable code responsible for managing the computer's resources, such as allocating memory, creating processes, and scheduling programs for execution. The kernel resides in RAM (random access memory) whenever HP-UX is running.

LANG

An environment variable used to inform a computer process of the user's requirements for native language, local customs, and coded character set.

legacy device special file

A special file associated with an I/O device (tape, disk, and so on), locked to a particular physical hardware path, containing hardware path information such as SCSI bus, target, and LUN in the device file name and minor number. See intro(7) for more information.

legacy hardware path

A hardware path following the legacy format conventions, that is, a series of bus-nexus addresses separated by / (slash) characters, leading to a host bus adapter (HBA). Beneath the HBA, additional address elements are separated by . (period) characters. All elements are represented in decimal. See intro(7) for more information.

library

A file containing a set of subroutines and variables that can be accessed by user programs. Libraries can be either archives or shared libraries. For example, /usr/lib/libc.a and /usr/lib/libc.sl are libraries containings all functions of Section 2 and all functions of Section 3 that are marked (3C) and (3S) in the HP-UX Reference. Similarly, /usr/lib/libm.a and /usr/lib/libm.sl are libraries containing all functions in Section 3 that are marked (3M) in the HP-UX Reference. See intro(2) and intro(3C).

LIF

See Logical Interchange Format.

line

A sequence of text characters consisting of zero or more nonnewline characters plus a terminating newline character.

link

Link is a synonym for directory entry. It is an object that associates a file name with any type of file. The information constituting a link includes the name of the file and where the contents of that file can be found on a mass storage medium. One physical file can have several links to it. Several directory entries can associate names with a given file. If the links appear in different directories, the file may or may not have the same name in each. However, if the links appear in one directory, each link must have a unique name in that directory. Multiple links to directories are not allowed (except as created by a user with appropriate privileges). See ln(1), link(2), unlink(2), and symbolic link.

Also, to prepare a program for execution; see linker.

link count

The number of directory entries that refer to a particular file.

linker

A program that combines one or more object programs into one program, searches libraries to resolve user program references, and builds an executable file in a.out format. This executable file is ready to be executed through the program loader, exec(2). The linker is invoked with the ld(1) command. The linker is often called a link editor.

local customs

The conventions of a geographical area or territory for such things as date, time and currency formats.

localization

The process of adapting existing software to meet the local language, customs, and character set requirements of a particular geographical area.

Logical Interchange Format (LIF)

A standard format for mass storage implemented on many Hewlett-Packard computers to aid in media transportability. See lif(4) for more detail.

login

The process of gaining access to HP-UX. This consists of successful execution of the login sequence defined by login(1), which varies depending on the system configuration. It requests a login name and possibly one or more passwords.

login directory

The directory in which you are placed immediately after you log in. This directory is defined for each user in the file /etc/passwd. The shell variable HOME is set automatically to your login directory by login(1) immediately after you log in. See home directory.

LUN

LUN refers to an end device, such as a disk or tape or a piece of logical storage in a disk array (mass storage term). Also known as a Logical Unit (LU).

LUN hardware path

A virtualized path that can represent multiple paths to a single mass storage device. It starts with a virtual bus-nexus (known as the virtual root node) with an address of 64000. Addressing beneath that virtual root node consists of a virtual bus address and a virtual LUN identifier, delimited by / (slash) characters. See intro(7) for more information.

lunpath hardware path

A hardware path to a LUN. It is composed of a series of bus-nexus addresses separated by / (slash) characters, leading to a host bus adopter (HBA). Beneath the HBA, additional address elements are represented in hexadecimal. The first elements represent a transport-dependent target address. The final element is a LUN address, which is the 64-bit representation of the LUN identifier reported by the target. See intro(7) for more information.

magic number

The first word of an a.out format or archive file. This word contains the system ID, which states what machine (hardware) the file will run on, and the file type (executable, sharable executable, archive, etc.).

major number

A number used exclusively to create special files that enable I/O to or from specific devices. This number indicates which device driver to use for the device. Refer to mknod(2) and the System Administrator manual supplied with your system for details.

message catalog

Program strings, such as program messages and prompts, are stored in a message catalog corresponding to a particular geographical area. Retrieval of a string from a message catalog is based on the value of the user's LANG environment variable (see LANG).

message queue identifier (msqid)

A unique positive integer created by a msgget(2) system call. Each msqid has a message queue and a data structure associated with it. The data structure is referred to as msqid_ds and contains the following members:

Message queue identifiers can be created using ftok(3C).

msg_perm is a ipc_perm structure that specifies the message operation permission (see below). This structure includes the following members:

msg_qnum is the number of messages currently on the queue. msg_qbytes is the maximum number of bytes allowed on the queue. msg_lspid is the process id of the last process that performed a msgsnd operation. msg_lrpid is the process id of the last process that performed a msgrcv operation. msg_stime is the time of the last msgsnd operation, msg_rtime is the time of the last msgrcv operation, and msg_ctime is the time of the last msgctl(2) operation that changed a member of the above structure.

message operation permissions

In the msgop(2) and msgctl(2) system call descriptions, the permission required for an operation is indicated for each operation. Whether a particular process has these permissions for an object is determined by the object's permission mode bits as follows:

Read and Write permissions on a msqid are granted to a process if one or more of the following are true:

Otherwise, the corresponding permissions are denied.

metacharacter

A character that has special meaning to the HP-UX shell, as well as to commands such as ed, find, and grep (see ed(1), find(1), and grep(1)). The set of metacharacters includes: !, " , &, ', *, ;, <, >, ?, [, ], `, and |. Refer to sh(1) and the related shell manual entries for the meaning associated with each. See also regular expression.

minor number

A number that is an attribute of special files, specified during their creation and used whenever they are accessed, to enable I/O to or from specific devices. This number is passed to the device driver and is used to select which device in a family of devices is to be used, and possibly some operational modes. The exact format and meaning of the minor number depends both on the driver and on the addressing format (legacy or agile) being used. In legacy format, the minor number encodes path information, but in agile format, the minor number is opaque and based on the WWID.

mode

A 16-bit word associated with every file in the file system, stored in the inode. The least-significant 12 bits of the mode determine the read, write, and execute permissions for the file owner, file group, and all others, and contain the set-user-ID, set-group-ID, and sticky bits. The least-significant 12 bits can be set by the chmod(1) command if you are the file's owner or the superuser. These 12 bits are sometimes referred to as permission bits. The most-significant 4 bits specify the file type for the associated file and are set as the result of open(2) or mknod(2) system calls.

mountable file system

A removable blocked file system contained on some mass storage medium with its own root directory and an independent hierarchy of directories and files. See block special file and mount(1M).

msqid

See message queue identifier.

Multiplexer (MUX)

Multiplexer (MUX) is a high-speed serial communication multiple port product. It combines various signals for transmission over a single channel and provides intelligent communication functions to off-load CPU serial communication processing tasks.

multiuser state

The condition of the HP-UX operating system in which terminals (in addition to the system console) allow communication between the system and its users. By convention, multiuser run level is set at state 2, which is usually defined to contain all the terminal processes and daemons needed in a multiuser environment. Run levels are table driven, and are specified by init(1M), which sets the run level by looking at the file /etc/inittab. Do not confuse the multiuser system with the multiuser state. A multiuser system is a system which can have more than one user actively communicating with the system when it is in the multiuser state. The multiuser state removes the single-user restriction imposed by the single-user state (see single-user state, inittab(4)).

native language

A computer user's spoken or written language, such as Chinese, Dutch, English, French, German, Greek, Italian, Katakana, Korean, Spanish, Swedish, Turkish, and so on.

Network File System (NFS)

The Network File System (NFS) allows a client node to perform transparent file access over the network.

By using NFS, a client node operates on files residing on a variety of servers and server architectures, and across a variety of operating systems. File access calls on the client (such as read requests) are converted to NFS protocol requests and sent to the server system over the network. The server receives the request, performs the actual file system operation, and sends a response back to the client.

NFS operates in a stateless manner using remote procedure calls (RPC) built on top of an external data representation (XDR) protocol. The RPC protocol enables version and authentication parameters to be exchanged for security over the network.

A server grants access to a specific file system to clients by adding an entry for that file system to the server's /etc/dfs/dfstab file.

Native Language Support (NLS)

A feature of HP-UX that provides the user with internationalized software and the application programmer with tools to develop this software.

newline character

The character with an ASCII value of 10 (line feed) used to separate lines of characters. It is represented by \n in the C language and in various utilities. The terminal driver normally interprets a carriage-return/line-feed sequence sent by a terminal as a single newline character (but see tty(7) for full details)

NLS

See Native Language Support.

NLSPATH

An environment variable used to indicate the search path for message catalogs (see message catalog).

node name

A string of bytes which uniquely identifies the system in the local network. Unlike the host name, the node name cannot include domain names. It can be viewed and/or set with the uname(1) command. The node and host names are usually set to the same value as application programs sometimes use the node and host names interchangeably.

nonspacing characters

Characters, such as a diacritical mark or accents, that are used in combination with other characters to form composite graphic symbols commonly found in non-English languages.

open file

A file that is currently associated with a file descriptor.

open file description

A record of how a process or a group of processes is accessing a file. Each file descriptor refers to exactly one open file description, but an open file description can be referred to by more than one file descriptor. The file offset, file status flags, and file access modes are attributes of an open file description.

ordinary file

A type of HP-UX file containing ASCII text (for example, program source), binary data (for example, executable code), etc. Ordinary files can be created by the user through I/O redirection, editors, or HP-UX commands.

orphan process

A child process that is left behind when a parent process terminates for any reason. The init process (see init(1M)) inherits (that is, becomes the effective parent of) all orphan processes.

orphaned process group

A process group in which the parent of every member is either itself a member of the group or is not a member of the group's session.

owner

The owner of a file is usually the creator of that file. However, the ownership of a file can be changed by the superuser or the current owner with the chown(1) command or the chown(2) system call. The file owner is able to do whatever he wants with his files, including remove them, copy them, move them, change their contents, etc. The owner can also change the files' modes.

parent directory

The directory one level above a directory in the file hierarchy. All directories except the root directory (/) have one (and only one) parent directory. The root directory has no parent. See also dot and dot-dot.

parent process

Whenever a new process is created by a currently-existing process (via fork(2)), the currently existing process is said to be the parent process of the newly created process. Every process has exactly one parent process (except the init process, see init), but each process can create several new processes with the fork(2) system call. The parent process ID of any process is the process ID of its creator.

parent process ID

A new process is created by a currently active process. The parent process ID of a process is the process ID of its creator for the lifetime of the creator. After the creator's lifetime has ended, the parent process ID is the process ID of init.

password

A string of ASCII characters used to verify the identity of a user. Passwords can be associated with users and groups. If a user has a password, it is automatically encrypted and entered in the second field of that user's line in the /etc/passwd file. A user can create or change his or her own password by using the passwd(1) command.

path name

A sequence of directory names separated by slashes, and ending with any file name. All file names except the last in the sequence must be directories. If a path name begins with a slash (/), it is an absolute path name; otherwise, it is a relative path name. A path name defines the path to be followed through the hierarchical file system in order to find a particular file.

More precisely, a path name is a null-terminated character string constructed as follows:

where <file-name> is a string of one or more characters other than the ASCII slash and null, and <dirname> is a string of one or more characters (other than the ASCII slash and null) that names a directory. File and directory names can consist of up to 14 characters on systems supporting short file names and up to 255 characters on systems supporting long file names.

A slash (/) by itself names the root directory. Two or more slashes in succession (////...) are treated as a single slash.

Unless specifically stated otherwise, the null or zero-length path name is treated as though it named a nonexistent file.

path name resolution

The process that resolves a path name to a particular file in a file hierarchy. Multiple path names can resolve to the same file, depending on whether resolution is sought in absolute or relative terms (see below). Each file name in the path name is located in the directory specified by its predecessor (for example, in the path name fragment a/b, file b is located in directory a). Path name resolution fails if this cannot be accomplished.

If the path name begins with a slash, the predecessor of the first file name in the path name is understood to be the root directory of the process, and the path name is referred to as an absolute path name. If the path name does not begin with a slash, the predecessor of the first file name of the path name is understood to be the current working directory of the process, and the path name is referred to as a relative path name. A path name consisting of a single slash resolves to the root directory of the process.

path prefix

A path name with an optional ending slash that refers to a directory.

permission bits

The nine least-significant bits of a file's mode are referred to as file permission bits. These bits determine read, write, and execute permissions for the file's owner, the file's group, and all others. The bits are divided into three parts: owner, group and other. Each part is used with the corresponding file class of processes. The bits are contained in the file mode, as described in stat(5). The detailed usage of the file permission bits in access decisions is described in file access permissions.

persistent device special file

A device file for mass storage devices, which is associated with a LUN hardware path, and thus transparently supports agile addressing and multipathing. In other words, a persistent device special file is unchanged if the LUN is moved from one host bus adapter (HBA) to another, moved from one switch/hub port to another, presented via a different target port to the host, or configured with multiple hardware paths. See intro(7) for more information on device special files.

PIC

See position-independent code.

pipe

An interprocess I/O channel used to pass data between two processes. It is commonly used by the shell to transfer data from the standard output of one process to the standard input of another. On a command line, a pipe is signaled by a vertical bar (|). Output from the command to the left of the vertical bar is channeled directly into the standard input of the command on the right.

portable file name character set

The following set of graphical characters are portable across conforming implementations of IEEE Standard P1003.1:

The last three characters are the dot, underscore and hyphen characters, respectively. The hyphen should not be used as the first character of a portable file name.

position-independent code (PIC)

Object code that can run unmodified at any virtual address. Position-independent code can use PC-relative addressing modes and/or linkage tables. It is most often used in shared libraries, in which case the linkage tables are initialized by the dynamic loader. Position-independent code is generated when the +z or +Z compiler option is specified.

privileged groups

A privileged group is a group that has had a setprivgrp (see getprivgrp(2)) operation performed on it, giving it access to some system calls otherwise reserved for the superuser. See appropriate privileges.

process

An invocation of a program, or the execution of an image (see image). Although all commands and utilities are executed within processes, not all commands or utilities have a one-to-one correspondence with processes. Some commands (such as cd) execute within a process, but do not create any new processes. Others (such as in the case of ls | wc -l) create multiple processes. Several processes can be running the same program, but each can be different data and be in different stages of execution. A process can also be thought of as an address space and single thread of control that executes within that address space and its required system resources. A process is created by another process issuing the fork(2) function. The process that issues fork(2) is known as the parent process and the new process created by the fork(2) as the child process.

process 1

See init.

process group

Each process in the system is a member of a process group. This grouping permits the signaling of related processes. A newly created process joins the process group of its creator.

process group ID

Each process group in the system is uniquely identified during its lifetime by a process group ID, a positive integer less than or equal to PIC_MAX. A process group ID cannot be reused by the system until the process group lifetime ends.

process group leader

A process group leader is a process whose process ID is the same as its process group ID.

process group lifetime

A period of time that begins when a process group is created and ends when the last remaining process in the group leaves the group, either due to process termination or by calling the setsid(2) or setpgid(2) functions.

process ID

Each active process in the system is uniquely identified during its lifetime by a positive integer less than or equal to PID_MAX called a process ID. A process ID cannot be reused by the system until after the process lifetime ends. In addition, if there exists a process group whose process group ID is equal to that process ID, the process ID cannot be reused by the system until the process group lifetime ends.

process lifetime

After a process is created with a fork(2) function, it is considered active. Its thread of control and address space exist until it terminates. It then enters an inactive state where certain resources may be returned to the system, although some resources, such as the process ID are still in use. When another process executes a wait(), wait3(), or waitpid() function (see wait(2)) for an inactive process, the remaining resources are returned to the system. The last resource to be returned to the system is the process ID. At this time, the lifetime of the process ends.

program

A sequence of instructions to the computer in the form of binary code (resulting from the compilation and assembly of program source).

prompt

The characters displayed by the shell on the terminal indicating that the system is ready for a command. The prompt is usually a dollar sign ($) for ordinary users (% in the C shell) and a pound sign (#) for the superuser, but you can redefine it to be any string by setting the appropriate shell variable (see sh(1) and related entries). See also secondary prompt.

quit signal

The SIGQUIT signal (see signal(2). The quit signal is generated by typing the character defined by the teletype handler as your quit signal. (See stty(1), ioctl(2), and termio(7).) The default is the ASCII FS character (ASCII value 28) generated by typing Ctrl-\. This signal usually causes a running program to terminate and generates a file containing the "core image" of the terminated process. The core image is useful for debugging purposes. (Some systems do not support core images, and on those systems no such file is generated.)

radix character

The character that separates the integer part of a number from the fractional part. For example, in American usage, the radix character is a decimal point, while in Europe, a comma is used.

raw disk

The name given to a disk for which there exists a character special file that allows direct transmission between the disk and the user's read or write buffer. A single read or write call results in exactly one I/O call.

read-only file system

A characteristic of a file system that prevents file system modifications.

real group ID

A positive integer which is assigned to every user on the system. The association of a user and his or her real group ID is done in the file /etc/passwd. The modifier "real" is used because a user can also have an effective group ID. The real group ID can then be mapped to a group name in the file /etc/group, although it need not be. Thus, every user is a member of some group (which can be nameless), even if that group has only one member.

Every time a process creates a child process (via fork(2)), that process has a real group ID equal to the parent process's real group ID. This is useful for determining file access privileges within the process.

real user ID

A positive integer which is assigned to every user on the system. A real user ID is assigned to every valid login name in the file /etc/passwd. The modifier "real" is used because a user can also have an effective user ID (see effective user ID).

Every time a process creates a child process (via fork(2)), that process has a real user ID equal to the parent process's real user ID. This is useful for determining file access privileges within the process.

regular expression

A string of zero or more characters that selects text. All the characters contained in the string might be literal, meaning that the regular expression matches itself only; or one or more of the characters might be a metacharacter, meaning that a single regular expression could match several literal strings. Regular expressions are most often encountered in text editors (such as ed(1), ex(1), or vi(1)), where searches are performed for a specific piece of text, or in commands that were created to search for a particular string in a file (most notably grep(1)). Regular expressions are also encountered in the shell, especially when referring to file names on command lines.

regular file

A type of file that is a randomly accessible sequence of bytes, with no further structure imposed by the system. Its size can be extended. A regular file is also called an ordinary file.

relative path name

A path name that does not begin with a slash (/). It indicates that a file's location is given relative to your current working directory, and that the search begins there (instead of at the root directory). For example, dir1/file2 searches for the directory dir1 in your current working directory; then dir1 is searched for the file file2.

__restrict

A macro that is optionally applied to the function prototype when the application developer directly or indirectly selects C99 conformance. If the user chooses C99 conformance, the __restrict macro is changed to the restrict keyword. Otherwise, the __restrict macro is expanded to an empty string.

root directory

root volume

The mass storage volume which contains the boot area (which contains the HP-UX kernel) and the root directory of the HP-UX file system.

saved group ID

Every process has a saved group ID that retains the process's effective group ID from the last successful exec(2) or setresgid() (see setresuid(2)), or from the last superuser call to setgid() (see setuid(2)) or setresuid(2). setgid() permits a process to set its effective group ID to this remembered value. Consequently, a process that executes a program with the set-group-ID bit set and with a group ID of 5 (for example) can set its effective group ID to 5 at any time until the program terminates. See exec(2), setuid(2), saved user ID, effective group ID, and set-group-ID bit. The saved group ID is also known as the saved set-group-ID.

saved process group ID

Every process has a saved process group ID that retains the process's group ID from the last successful exec(2). See setpgrp(2), termio(7), and process group ID.

saved user ID

Every process has a saved user ID that retains the process's effective user ID from the last successful exec(2) or setresuid(2), or from the last superuser call to setuid(2). setuid(2) permits a process to set its effective user ID to this remembered value. Consequently, a process which executes a program with the set-user-ID bit set and with an owner ID of 5 (for example) can set its effective user ID to 5 at any time until the program terminates. See exec(2), setuid(2), saved group ID, effective user ID, and set-user-ID bit. The saved user ID is also known as the saved set-user-ID.

saved set-group-ID

See saved group ID.

saved set-user-ID

See saved user ID.

SCCS

See Source Code Control System.

Source Code Control System (SCCS)

A set of HP-UX commands that enables you to store changes to an SCCS file as separate "units" (called deltas). These units, each of which contains one or more textual changes to the file, can then be applied to or excluded from the SCCS file to obtain different versions of the file. The commands that make up SCCS are admin(1), cdc(1), delta(1), get(1), prs(1), rmdel(1), sact(1), sccsdiff(1), unget(1), val(1), and what(1).

SCCS file

An ordinary text file that has been modified so the Source Code Control System (SCCS) can be used with it. This modification is done automatically by the admin(1) command. See also delta.

secondary prompt

One or more characters that the shell prints on the display, indicating that more input is needed. This prompt is not encountered nearly as frequently as the shell's primary prompt (see prompt). When it occurs, it is usually caused by an omitted right quote on a string (which confuses the shell), or when you enter a shell programming language control-flow construct (such as a for construct) from the command line. By default, the shell's secondary prompt is the greater-than sign (>), but you can re-define it by setting the shell variable PS2 appropriately in your .profile file. (The C shell has no secondary prompt.)

semaphore identifier (semid)

A unique positive integer created by a semget(2) system call. Each semid has a set of semaphores and a data structure associated with it. The data structure is referred to as semid_ds and contains the following members:

Semaphore identifiers can be created using ftok(3C).

sem_perm is a ipc_perm structure that specifies the semaphore operation permission (see below). This structure includes the following members:

The value of sem_nsems is equal to the number of semaphores in the set. Each semaphore in the set is referenced by a positive integer referred to as a sem_num. sem_num values run sequentially from 0 to the value of sem_nsems minus 1. sem_otime is the time of the last semop(2) operation, and sem_ctime is the time of the last semctl(2) operation that changed a member of the above structure.

semaphore operation permissions

In the semop(2) and semctl(2) system call descriptions, the permission required for an operation is indicated for each operation. Whether a particular process has these permissions for an object is determined by the object's permission mode bits as follows:

Read and Alter permissions on a semid are granted to a process if one or more of the following are true:

Otherwise, the corresponding permissions are denied.

semid

See semaphore identifier.

session

Each process group is a member of a session. A process is considered to be a member of the session of which its process group is a member. A newly created process joins the session of its creator. A process can alter its session membership (see setsid(2)). A session can have multiple process groups (see setpgid(2)).

session leader

A process that has created a session (see setsid(2)).

session lifetime

The period between when a session is created and the end of the lifetime of all process groups that remain as members of the session.

set-group-ID bit

A single bit in the mode of every file in the file system. If a file is executed whose set-group-ID bit is set, the effective group ID of the process which executed the file is set equal to the real group ID of the owner of the file. See also group.

set-user-ID bit

A single bit in the mode of every file in the file system. If a file is executed whose set-user-ID bit is set, the effective user ID of the process that executed the file is set equal to the real user ID of the owner of the file.

shared library

An executable file that can be shared between several different programs. Code from a shared library is not linked into the program by ld(1), but is instead mapped into the process's address space at run time by the dynamic loader. Shared libraries must contain position-independent code, and are created by ld(1). They typically have the file name suffix .sl.

shared memory identifier (shmid)

A unique positive integer created by a shmget(2) system call. Each shmid has a segment of memory (referred to as a shared memory segment) and a data structure associated with it. The data structure is referred to as shmid_ds and contains the following members:

Shared memory identifiers can be created using ftok(3C).

shm_perm is a ipc_perm structure that specifies the permission for a shmop(2) or shmctl(2) operation (see below). This structure includes the following members:

shm_segsz specifies the size of the shared memory segment. shm_cpid is the process id of the process that created the shared memory identifier. shm_lpid is the process id of the last process that performed a shmop(2) operation. shm_nattch is the number of processes that currently have this segment attached. shm_atime is the time of the last shmat operation, shm_dtime is the time of the last shmdt operation, and shm_ctime is the time of the last shmctl(2) operation that changed one of the members of the above structure.

shared memory operation permissions

In the shmop(2) and shmctl(2) system call descriptions, the permission required for an operation is indicated for each operation. Whether a particular process has the permission to perform a shmop(2) or shmctl(2) operation on an object is determined by the object's permission mode bits as follows:

Read and Write permissions for a shmop(2) or shmctl(2) operation on a shared memory identifier (shmid ) are granted to a process if one or more of the following are true:

Otherwise, the corresponding permissions are denied.

shell

A user interface to the HP-UX operating system. A shell often functions as both a command interpreter and an interpretive programming language. A shell is automatically invoked for every user who logs in. See sh(1) and its related manual entries plus the tutorials supplied with your system for details.

shell program

See shell script.

shell script

A sequence of shell commands and shell programming language constructs stored in a file and invoked as a user command (program). No compilation is needed prior to execution because the shell recognizes the commands and constructs that make up the shell programming language. A shell script is often called a shell program or a command file. See the Shells User Guide.

shmid

See shared memory identifier.

signal

A software interrupt sent to a process, informing it of special situations or events. Also, the event itself. See signal(2).

single-user state

A condition of the HP-UX operating system in which the system console provides the only communication mechanism between the system and its user. By convention, single-user state is usually specified by init(1M) as run-level S or s. Do not confuse single-user state, in which the software is limiting a multiuser system to a single-user communication, with a single-user system, which can never communicate with more than one fixed terminal. See also multiuser state.

slash

The literal character /. A path name consisting of a single slash resolves to the root directory of the process. See also path name resolution.

solidus

See slash.

source code

The fundamental high-level information (program) written in the syntax of a specified computer language. Object (machine-language) code is derived from source code. When dealing with an HP-UX shell command language, source code is input to the command language interpreter. The term shell script is synonymous with this meaning. When dealing with the C Language, source code is input to the cc(1) command. Source code can also refer to a collection of sources meeting any of the above conditions.

special file

A file associated with an I/O device. Often called a device file. Special files are read and written the same as ordinary files, but requests to read or write result in activation of the associated device. Due to convention and consistency, these files should always reside in the /dev directory. See also file.

special system processes

Special system processes are those which are critical to basic system operation. They include: the scheduler, the initialization process (also known as init) and the pager.

SS/80

See CS/80.

standard error

The destination of error and special messages from a program, intended to be used for diagnostic messages. The standard error output is often called stderr, and is automatically opened for writing on file descriptor 2 for every command invoked. By default, the user's terminal is the destination of all data written to standard error, but it can be redirected elsewhere. Unlike standard input and standard output, which are never used for data transfer in the "wrong" direction, standard error is occasionally read. This is not recommended practice, since I/O redirection is likely to break a program doing this.

standard input

The source of input data for a program. The standard input file is often called stdin, and is automatically opened for reading on file descriptor 0 for every command invoked. By default, the user's terminal is the source of all data read from standard input, but it can be redirected from another source.

standard output

The destination of output data from a program. The standard output file is often called stdout, and is automatically opened for writing on file descriptor 1 for every command invoked. By default, the user's terminal is the destination of all data written to standard output, but it can be redirected elsewhere.

stderr

See standard error.

stdin

See standard input.

stdout

See standard output.

stream

A term most often used in conjunction with the standard I/O library routines documented in Section 3 of this manual. A stream is simply a file pointer (declared as FILE *stream) returned by the fopen(3S) library routines. It may or may not have buffering associated with it (by default, buffering is assigned, but this can be modified with setbuf(3S)).

sticky bit

A single bit in the mode of every file in the file system. The sticky bit has no significance if it is set on a regular file.

If set on a directory, the files in that directory can be removed or renamed only by the owner of the file, the owner of the directory containing the file, or superuser. See also chmod(2), rename(2), rmdir(2), and unlink(2).

subdirectory

A directory that is one or more levels lower in the file system hierarchy than a given directory. Sometimes called a subordinate directory.

subordinate directory

See subdirectory.

Subset 1980

See CS/80.

superblock

A block on each file system's mass storage medium which describes the file system. The contents of the superblock vary between implementations. Refer to the system administrator manuals supplied with your system for details.

superuser

The HP-UX system administrator. This user has access to all files, and can perform privileged operations. superuser has a real user ID and effective user ID of 0, and, by convention, the user name of root.

superior directory

See parent directory.

supplementary group ID

A process has up to sysconf(_SC_NGROUPS_MAX) supplementary group IDs used in determining file access permissions, in addition to the effective group ID. The supplementary group IDs of a process are set to the supplementary group IDs of the parent process when the process is created. Note that the value returned from sysconf(_SC_NGROUPS_MAX) may be larger than the value of NGROUPS_MAX found in <limits.h> on certain HP-UX systems.

symbolic link

A type of file that indirectly refers to a path name. See symlink(4).

system

The HP-UX operating system. See also kernel.

system asynchronous I/O

A method of performing I/O whereby a process informs a driver or subsystem that it wants to know when data has arrived or when it is possible to perform a write request. The driver or subsystem maintains a set of buffers through which the process performs I/O. See ioctl(2), read(2), select(2), and write(2) for more information.

system call

An HP-UX operating system kernel function available to the user through a high-level language (such as FORTRAN, Pascal, or C). Also called an "intrinsic" or a "system intrinsic." The available system calls are documented in Section 2 of the HP-UX Reference.

system console

A keyboard and display (or terminal) given a unique status by HP-UX and associated with the special file /dev/console. All boot ROM error messages, HP-UX system error messages, and certain system status messages are sent to the system console. Under certain conditions (such as the single-user state), the system console provides the only mechanism for communicating with HP-UX. See the System Administrator manuals and user guides provided with your system for details on configuration and use of the system console.

system process

A system process is a process that runs on behalf of the system. It may have special implementation-defined characteristics.

terminal

A character special file that obeys the specifications of termio(7).

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 characters, 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, an effective user ID, or a saved user ID.

UTC

See Epoch.

utility

An executable file, which might contain executable object code (that is, a program), or a list of commands 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 Administrator 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 interpret some, but not necessarily all, whitespace characters as delimiters for fields, words, or command options.

working directory

Each process has associated with it the concept of a current working directory. For a shell, this appears as the directory in which you currently "reside". This is the directory in which relative path name (that is, a path name that does not begin with /) searches begin. It is sometimes referred to as the current directory, or the current working directory.

zombie process

The name given to a process which terminates for any reason, but whose parent process has not yet waited for it to terminate (via wait(2)). The process which terminated continues to occupy a slot in the process table until its parent process waits for it. Because it has terminated, however, there is no other space allocated to it either in user or kernel space. It is therefore a relatively harmless occurrence which will rectify itself the next time its parent process waits. The ps(1) command lists zombie processes as defunct.