Glossary

The most important terms used in the manual are listed and explained here in alphabetical order.

8-bit transparency

The ability of a software component to process 8-bit characters without modifying or utilizing any part of the character in a way that is inconsistent with the rules of the current coded character set.

absolute pathname

A pathname beginning with the root directory of the POSIX file system and leading to a specific file or directory. Every file and every directory has a unique absolute pathname (see pathname resolution).

access mode

The method used to access the records of a file.

account number

BS2000:
Designates an account for the associated user ID. Multiple user IDs may be assigned the same account number. Each user ID can be provided with a maximum of 60 account numbers. The account number is evaluated at LOGON and at the time of an ENTER-JOB.

address

In general, a number used to specify a memory location.

address space

The memory area that can be accessed by a process.

alert

An audible or visual indication at the user ́s terminal that an error or some other event has occurred. When the standard output is directed to a terminal device, the method for alerting the terminal user is unspecified. When the standard output is not directed to a terminal device, the alert is accomplished by writing the alert character to standard output.

alert character

A character that in the output stream should cause a terminal to alert its user via a visual or audible signal. The alert character is the character designated by \a in the C language. It is unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the alert function.

alias name

A word consisting solely of underscores ( _ ) , digits, alphabetic characters from the portable character set, and the characters !, %, and @. Other implementations may allow other characters within alias names as an extension.

appropriate privileges

Special privileges needed by some of the function calls and function call options defined in the this manual. In accordance with the POSIX standard, this term supersedes the older concept of system administrator privileges.

argument

In the shell, an argument is a parameter that is passed to a utility. This parameter is the equivalent of a single string in the argv array created by one of the exec functions. An argument can be one of the options, option-arguments or operands following the command name.
In the C language, an argument is a string that passes data to a function. The arguments of a function are specified within parentheses, which follow the function name. The number of arguments may also be zero. If two or more arguments are specified, they must be delimited by commas. The definition of a function includes a description of the number and types of arguments.

authentication

A verification of user entries when logging on at the system. The user attributes "user ID" and "password" are checked against the entries in the join file (also called a user catalog).

background

A method of executing a program in which no dialog between the user and computer occurs during program execution. The shell displays its prompt while the program is executing, so further commands may be invoked at the terminal (see foreground).

background process

A process which is a member of a background process group and which does not fully utilize system resources, but allows the simultaneous execution of other (generally more important) processes. A background process normally utilizes time gaps in which the processor would be otherwise unoccupied.

background process group

Any process group, other than a foreground process group, that is a member of a session that has established a connection with a controlling terminal.

backslash

The character \, also known as a reverse solidus.

backspace character

A character that, in the output stream, should cause printing (or displaying) to occur one column position previous to the position about to be printed. If the position about to be printed or displayed is at the first column of the current line, the behavior is unspecified. The backspace is the character designated by \b in the C language. It is unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the backspace function.

binary file

An ordered sequence of bytes. The data written by C output functions is transferred to a binary file on a 1:1 basis. In contrast to text files, control characters for line feeds and tabs are non converted (see text file), but are mapped as corresponding EBCDIC values. Data that is read from a binary file thus corresponds precisely to the data that was originally written to the file.
The following files are binary files with stream-oriented I/O: cataloged PAM files, temporary PAM files (INCORE), and cataloged SAM files that were opened with fopen() or freopen() in binary mode.
The following files are binary files with record-oriented I/O: cataloged ISAM files, cataloged SAM files, and cataloged PAM files that were opened with
the function fopen() or freopen() in binary mode and with the option "type=record".
Binary mode can only be specified with the fopen() and freopen() functions. The elementary functions open() and creat() always open SAM and ISAM files as text files.

block special file

A special file for block-oriented I/O devices. A block special file is normally distinguished from a character special file by the fact that it provides access to the device in a manner such that the hardware characteristics of the device are not visible.

block-mode terminal

A terminal that does not support character-based input and output operations.

buffer

A memory area in which data is temporarily stored.

buffering

For all output functions that write data to text files and binary files with streamoriented I/O (printf(), putc(), fwrite() etc.), data is initially stored in a buffer and is not written to the external file until a specific event occurs. This differs for text and binary files.

carriage-return character

A character that in the output stream indicates that printing should start at the beginning of the same physical line in which the carriage-return character occurred. The carriage-return is the character designated by \r in the C language. It is unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the movement to the beginning of the line.

character

A sequence of one or more bytes representing a single graphic symbol or control code. This term also applies to multi-byte characters and single-byte characters, where a single-byte character is a special case of a multi-byte character.

character class

A named set of characters sharing an attribute associated with the name of the class. The classes and the characters contained in the set are dependent on the value of the LC_CTYPE category in the current locale.

character set

In the international "C" locale, characters are encoded according to the rules of the 7-bit US ASCII coded character set. Each character of the character set is assigned various attributes, such as a graphic symbol, possible conversions into corresponding uppercase or lowercase letters, the character class to which it belongs, and a position within the codeset collating sequence. Different native language character sets could be used in internationalized programs.

character special file

A special file for character-oriented I/O devices. One example of a character special file is a terminal device file.

character string

A contiguous sequence of characters that contains a null byte as the last element.

child directory

A directory that is under another directory at the next-higher level of the file system.

child process

See process.

clock tick

The (machine-specific) number of intervals per second is defined by{CLK_TCK}. It is used to express the value in type clock_t as returned by time.h.

collating element

The smallest entity used to determine the logical ordering of character or widecharacter strings (see collation sequence). A collating element consists of either a single character, or two or more characters collating as a single entity. The value of the LC_COLLATE category in the current locale determines the current set of collating elements.

collating sequence

The relative order of collating elements, as determined by the setting of the LC_COLLATE category in the current locale.
The character order, as defined for the LC_COLLATE category in the current locale, defines the relative order of all collating elements, such that each element occupies a unique position in the order. This is the order used in ranges of characters and collating elements in regular expressions and pattern matching. In addition, the definition of the collating weights of characters and collating elements uses collating elements to represent their respective positions within the collation sequence.
Multi-level sorting is accomplished by assigning the collating elements one or more collation weights, up to the limit {COLL_WEIGHTS_MAX} (see the header file limits.h).
On each level, elements may be given the same weight (at the primary level, called an equivalence class; see equivalence class) or be omitted from the sequence. Strings that collate equal using the first assigned weight (primary ordering) are then compared using the next assigned weight (secondary ordering), and so on.

collation order

The logical ordering of character or wide-character strings according to defined precedence rules. These rules identify a collation sequence between the collating elements, and such additional rules that can be used to order strings consisting of multiple collating elements.

column position

The distance of a character from the start of a line. It is assumed that each character in a character set has an intrinsic column width independent of any output device. Each printable character in the portable character set has a column width of one. The XPG4 standard utilities, when used as described in this manual, assume that all characters have integral column widths. The column width of a character is not necessarily related to the internal representation of the character (numbers of bits or bytes).
The column position of a character in a line is defined as one plus the sum of the column widths of the preceding characters in the line.

command

A directive to the shell to perform a particular task (see the manual "POSIX Commands”).

command interpreter

An interface that interprets sequences of text input as commands. It may operate on an input stream or it may interactively prompt and read commands from a terminal. It is possible for applications to invoke utilities through a number of interfaces, which are collectively considered to act as command interpreters. The most obvious of these are the sh utility and the system() function, although popen() and the various forms of exec may also be considered to behave as interpreters.

control character

A character, other than a graphic character, that affects the recording, processing, transmission or interpretation of text.

controlling process

The session leader that established the connection to the controlling terminal. If the terminal ceases 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 may 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 process group associated with the controlling terminal.

core dump

An image of the memory area occupied by a specific process. If the process is aborted, the core dump is written to the file core.

current (or working) directory

A directory, associated with a process, that is used in pathname resolution for pathnames that do not begin with a slash (/).

daemon

A background process that performs its activities silently once started and terminates only when the system is shut off. The best known UNIX example is the printer daemon, which handles the printing of a file in the background while the user continues working.

data set pointer (file pointer)

A data set pointer (also called a file pointer) is a pointer to a structure of type FILE. It is used to process a file with the standard access functions (see stdio.h). When a file is opened with fopen(), fdopen(), or freopen(), it is assigned a file pointer, which serves as a file argument when the file is subsequently accessed using fprintf(), fscanf(), fclose(), etc. At program startup, the standard I/O files are automatically opened with the following file pointers: stdin (standard input), stdout (standard output), stderr (standard error).

default

Normal method by which a program is executed when no additional specifications are made.

device ID

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

device

A non-negative integer used to identify a device.

directory

A file that contains directory entries with unique names (see file name). Directories are used to organize files and other directories into a hierarchical systeme.

directory entry (or link)

An object that associates a file name with a file. Several directory entries can associate names with the same file.

directory stream

A per-process unique value used to reference an open directory.

display (on-screen)

Output to the terminal device file. The output appears on the screen of themonitor. If the output is not directed to a terminal, the results are undefined.
The terms "display" and "write" are clearly differentiated in the XPG4 standard. When the term "display" is used, the method of outputting to the terminal is unspecified; termcap or terminfo is frequently used for this purpose, but this is not a requirement. The term "write" is reserved for cases when a file descriptor is used and the output can be redirected. However, when the writing is directly to the terminal (i.e. has not been redirected elsewhere), there is no practical way for a user or test suite to determine whether a file descriptor is being used or not. Therefore, the use of a file descriptor is mandated only for the redirection case.

dot

A file name consisting of a single dot character (.); it represents the current working directory (see pathname resolution).

dot-dot

A file name consisting solely of two dot characters (..); it represents the parent directory (see pathname resolution)..

downshifting

The conversion of uppercase characters to their corresponding lowercase representations.

effective group ID

An attribute of a process that is used in determining various permissions, including file access permissions (see group ID). This value is subject to change during the process lifetime, as described under setgid() and the exec family of functions.

effective user ID

An attribute of a process that is used in determining various permissions, including file access permissions (see user ID). This value is subject to change during the process lifetime, as described under setuid() and exec.

elementary functions

BS2000:
Functions that process a file on the basis of file descriptors are referred to as "elementary". This is in contrast to the standard I/O functions, all of which operate on the basis of file pointers. In addition, the elementary functions allow SAM files to be processed only as text files, whereas with the standard functions they can also be processed as binary files.
In UNIX/POSIX, elementary functions are implemented in the form of system calls, which differ from standard functions by virtue of improved performance and greater operating system support. No such distinction is made between a system call and a function in BS2000.

empty directory

A directory that contains, at most, directory entries for . and .. (see dot and dot-dot).

empty string

A string whose first byte is a null byte.

empty wide character string

A wide character string whose first element is a null wide-character code.

epoch

The time zero hours, zero minutes, zero seconds, on January 1, 1970 (Coordinated Universal Time).

BS2000:
The time zero hours, zero minutes, zero seconds, on January 1, 1970 local time.

equivalence class

A set of collating elements with the same primary collation weight. The following letters, for example, constitute an equivalence class, since they are all based on the same base letter and differ only in terms of their accents: á, à, â, ä, ã, å. The collation order of elements within an equivalence class is determined by the weights assigned on any subsequent levels after the primary weight.

executable file

A regular file which is accepted as a new process image by the exec family of functions, which has execute permission, and can thus be called as a command or utility. The standard utilities described as compilers can produce executable files, but other unspecified methods of producing executable files can also be provided. The internal format of an executable file is unspecified, but a conforming application can detect that an executable file is not a text file.

expression

A mathematical or logical symbol or a meaningful combination of such symbols.

extended security controls

The access control (see file access permissions) and privilege (see appropriate privileges) mechanisms have been defined to allow implementation-dependent extended security controls. These permit an implementation to provide security mechanisms that differ from those from those described in the XPG4 standard. These mechanisms do not alter or override the defined semantics of any of the functions described in this manual.

feature test macro

A macro used to determine whether a particular set of features will be included from a header.

FIFO special file

A type of file from which data is read on a first-in-first-out basis. Other properties of FIFO special files are described under lseek(), open(), read(), and write().

file

An object that can be written to, or read from, or both. A file is identified in UNIX by means of an inode has certain attributes, including access permissions and type. File types include regular file, character special file, block special file, FIFO special file and directory. A regular file contains text, data, programs or other information. A special file refers to a device or a part of a physical device such as a drive or hard disk partition. A directory contains other files.

BS2000:
Records that are related to one another are combined into a named unit (i.e. a file). Typical files include conventional I/O data of programs, load modules, and plaintext information that can be created and edited with an editor.

file access permissions

Part of the open file description. The file permission bits are used for file access control. These bits are set at the time of file creation by functions such as open(), creat(), mkdir() and mkfifo() and are changed by chmod(). The bits are read by stat() or fstat().
Applications may provide additional or alternate file access control mechanisms, or both. An alternate file access control mechanism must have the following features:

• It must specify file permission bits for the file owner class, file group class, and file other class of the file.

• It must be enabled only by explicit user action, on a per-file basis by the file owner or a user with the appropriate privileges.

• It may be disabled for a file after the file permission bits are changed for that file with chmod(). The disabling of the alternate mechanism need not disable any additional mechanisms defined by the implementation.

Whenever a process requests file access permission for a read, write, or execute/search operation, access is determined as described below (provided no additional mechanism denies access):

If a process has appropriate privileges:

• If read, write or directory search permission is requested, access is granted.

• If execute permission is requested, access is granted if execute permission is granted to at least one user by the file permission bits or by an alternate access control mechanism; otherwise, access is denied.

If a process does not have appropriate privileges:

• The file permission bits of a file contain read, write and execute/search permissions for the file owner class, file group class and file other class.

• Access is granted if an alternate access control mechanism is not enabled and the requested access permission bit is set for the class (file owner class, file group class, or file other class) to which the process belongs, or if an alternate access control mechanism is enabled and it allows the requested access; otherwise, access is denied.

file description

An object that contains information on how a process or group of processes are 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. A file offset, file status and file access modes are attributes of an open file description.

file descriptor

A per-process unique, positive integer used to establish a unique association between a process and an open file for the purpose of file access. The value of a file descriptor is from zero to {OPEN_MAX}. A process can have no more than {OPEN_MAX} file descriptors open simultaneously. File descriptors may also be used to implement message catalog descriptors and directory streams. See open file description in this Glossary and {OPEN_MAX} in the limits.h header.

file group class

A process is in the file group class of a file if the process is not in 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. Other conformant implementations may specify different members for this class.

file hierarchy

Files in the system are organized in a hierarchical tree structure in which all of the non-terminal nodes (branches) are directories and all of the terminal nodes (leaves) are any type of file. Multiple directory entries may refer to the same file.

file mode

A combination of attributes that specify the file type and the access permissions of a file (see the header file sys/stat.h).

file name

A name consisting of 1 to {NAME_MAX} bytes used to name a file. The characters composing the name may be selected from the set of all character values excluding the slash character (/) and the null byte (\0). The file names . (dot) and .. (dot-dot) have special meaning; see pathname resolution. File names are constructed from the portable file name character set, since the use of other characters can be confusing or ambiguous in certain contexts. For example, the use of a colon (:) in a pathname could cause ambiguity if that pathname were included in a PATH definition (see portable file name character set).

file offset

The file offset specifies the byte position in the file, i.e. the number of bytes from the start of the file (byte 1 = 1), where the next I/O operation begins. Each open file description associated with a regular file, block special file or directory has a file offset. A character special file that does not refer to a terminal device may have a file offset. There is no file offset specified for a pipe or FIFO.

file other class

The property of a file indicating access permissions for a process related to the user and group identification of a process. A process is in the file other class of a file if the process is not in the file owner class or file group class.

file owner class

The property of a file indicating access permissions for a process related to the user identification of a process.
A process is in the file owner class of a file if the effective user ID of the process matches the user ID of the file. Other conformant implementations may specify different members for this class.

file permission bits

Information about a file that is used, along with other information, to determine if a process has read, write or execute/search permission to a file. The bits are divided into three parts: owner, group and other. Each part is used with the corresponding file class of processes. These bits are contained in the file mode, as described under sys/stat.h. The detailed usage of the file permission bits in access decisions is described under file access permissions.

file position indicator

The file position indicator contains information on the current file position. Data is read from or written to the file from this current position onwards. The structure of the information contained in the file position indicator varies in accordance with the type of file.
For text files, it contains information on the current record and the position within that record.

BS2000:
For binary files with stream I/O, it contains the byte offset, i.e. the number of bytes calculated from the beginning of the file. The structure differs for SAM and ISAM files. This information is used internally by the runtime system.
For binary files with record I/O, it contains information on the position after the last record to be read, written or deleted, or the position reached by an directly preceding seek operation.
For ISAM files with duplicate keys, it contains the position after the last record of a group having identical keys if one of these records was read, written or deleted earlier.

file serial number

A per-file-system unique identifier for a file.

file status

The current status of a file.

file structure

As soon as a file is opened with fopen(), fdopen() or freopen(), it is automatically assigned a specific structure of type FILE. This structure is defined in stdio.h and includes, among other things, the following information on the file: pointer to the I/O buffer, buffer size, location of the file position indicator, and the size of the file.

file system

A collection of files and certain of their attributes. A UNIX file system is organized in a hierarchical structure (see file hierarchy). A file system provides a name space for file serial numbers referring to the files in it.

file times update

Each file has three associated time values that are updated when file data has been accessed, file data has been modified, or file status has been changed, respectively. These values are returned in the file characteristics structure stat (see sys/stat.h).
For each function in this manual that reads or writes file data or changes the file status, the appropriate time-related fields are noted as "marked for update". At the time of an update, all marked fields are set to the current time, and the update marks are cleared. Two such update times are when the file is no longer open by any process and when stat() or fstat() is performed on the file. Additional update times are unspecified. Updates are not done for files on readonly file systems.

filter

A command with which data is read from standard input or a list of input files and written to standard output. Typically, its function is to perform some transformation on the data stream.

foreground

Normal method of executing a command in a shell. When a command is executed in the foreground, the shell waits for that command to complete before prompting the user for further input.

foreground process

A process that is a member of a foreground process group.

foreground process group

A process group whose member processes have certain privileges, denied to processes in background process groups, when accessing their controlling terminal. Each session that has established a connection with a controlling terminal has exactly one process group of the session as the foreground process group of that controlling terminal.

foreground process group ID

The process group ID of the foreground process group.

form-feed character

A character that in the output stream indicates that printing should start on the next page of an output device. The form-feed is the character designated by \f in the C language. If the form-feed is not the first character of an output line, the result is unspecified. It is likewise unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the movement to the next page.

group database

A system database of implementation-dependent format that contains at least the following information for each group ID: group name, numerical group ID, and a list of users allowed in the group. The list of users allowed in the group is used by the newgrp utility.

group ID

A non-negative integer that is used to identify a group of system users. Each system user is a member of at least one group. 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 set-group-ID.

group name

A string that is used to identify a group, as described in group database. To be portable across XSI-conformant systems, the value must be composed of characters from the portable file name character set. The hyphen should not be used as the first character of a portable group name.

header file (include file)

The file containing data definitions which are copied by the compiler into source files (see library). Header file names end with the suffix .h. Header files are included in source files by means of an #include statement. Consequently, they are also referred to as include files.

home directory

The directory in which a user is automatically placed when connected with POSIX.

host

central computer in a network. A host is the system on which programs are executed, files are stored, and I/O is controlled. Large powerful networks may often have several hosts.

internationalization

The provision, within a computer program, of the capability of making itself adaptable to the requirements of different native languages, local customs and coded character sets.

interrupt

An interruption in the normal processing of a program. Interrupts are caused by signals which are triggered by a hardware state of a peripheral device to indicate a particular status. If the interrupt is detected by the hardware, an interrupt service routine is executed. An interrupt character is usually an ASCII character that generates an interrupt when it is entered from the keyboard.

job control

A facility that allows users selectively to stop (or suspend) the execution of processes and continue (or resume) their execution at a later point. The user typically employs this facility via the interactive interface jointly supplied by the terminal I/O driver and a command interpreter.

job control ID

A handle that is used to refer to a job. The job control job ID can have any of the following forms:

Job control job ID	Meaning
%%	Current job
%+	Current job
%-	Previous job
%n	Job number n
%string	Job whose command begins with string
%?string	Job whose command contains string

job variable

BS2000:
Job variables are named memory areas that are used for mutual data exchanges among jobs and for the exchange of information between jobs and the operating system. Each job variable has a name and a value (its content). The content can be used to control jobs and programs. Job variables can be created, modified, queried and deleted by the user. In addition, users can instruct the operating system to set a monitoring job variable to reflect changes in the status of a job or a program.

join file (user catalog)

A file containing the user attributes of all user IDs of a pubset or system.

kernel

The code of the POSIX/UNIX operating system.

library

A collection of statically linked object files or source files that can be linked in dynamically (shareable library). The individual files of a library contain the program text for one or more related functions. When a relevant function is called in the source code, the corresponding object file must be linked into the program (see header file). The name of the library containing it must be specified at linkage. The file containing the library function used is then copied into the source code of the application.

link

See directory entry.

link count

The number of directory entries that refer to a file is called the link count of the file.

local machine

As far as the user is concerned, the local machine is always the one on which he or she is working. All other computers on the network are remote computers for that user.

locale

The conventions of a geographic area or territory for date, time, and currency formats.

locale (country-specific)

The definition of the subset of a user ́s environment that depends on language and cultural conventions.

localization

The process of establishing information within a computer system specific to the operation of particular native languages, local customs and coded character sets.

login name

BS2000:
A user name of up to 8 characters that is entered in the join file. The login name is the basis on which the user is identified on gaining access to the system. All files and job variables are created under a login name. The names of files and job variables are stored together with a login name in the file catalog.

mathematical range

The notation [n, m] and [n, m) denotes a mathematical range. The square brackets [ and ] include the respective limits; the parentheses ( and ) exclude them. Thus, if x is in the range [0, 1], it can be from 0 to 1 inclusive, but if x is in [0, 1), it can be from 0 up to but not including 1.

memory area

A restricted (and defined) area of working memory that can be assigned to specific programs and arbitrarily subdivided in accordance with program requirements.

message catalog

A file or storage area containing program messages, command prompts and responses to prompts for a particular native language, territory and codeset.

message catalog descriptor

A per-process unique value used to identify an open message catalog.

mode

A collection of attributes that specifies a file ́s type and its access permissions (see file access permissions).

mount point

Either the system root directory or a directory for which the st_dev field of structure stat (see sys/stat.h) differs from that of its parent directory.

multi-byte character

Characters that consist of multiple bytes, regardless of whether a normal character or wide character code is involved.

NaN (not a number)

A value that can be stored in a floating type but that is not a valid floating point number. One example of such a bit pattern is a floating-point number whose exponent bits are all set to 1.

newline character

A character that in the output stream indicates that printing should start at the beginning of the next line. The newline is the character designated by \n in the C language. If the newline is not the first character of an output line, the result is unspecified. It is likewise unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the movement to the next line.

null byte

A byte with all bits set to zero.

null pointer

The value that is obtained by converting the number 0 into a pointer; for example, (void *) 0. The C language guarantees that this value will not match that of any legitimate pointer, so many functions that return pointers use it to indicate an error.

object file

A file that contains the source code of a program in binary representation. A relocatable object file contains references that have not been resolved by associations with the corresponding definitions; an executable object file is a linked program.

open file

A file that is currently associated with a file descriptor.

option

An argument to a command that affects the execution of that command. An option is a type of argument that follows the command name and usually precedes the other arguments on the command line. Options normally begin with a minus sign. The number and types of arguments allowed vary for different commands. If options also take arguments, the arguments are separated by spaces.

option-argument

A parameter that follows certain options. In some cases, an option-argument is included within the same argument string as the option; in most cases, it is the next argument.

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.

parent directory

The directory containing a directory entry for the file in question. This concept does not apply to . and .. (dot and dot-dot).

parent process

See process.

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 the init process.

parser

A parser performs a syntactic and lexical analysis of a text.

password

A sequence of characters that must be entered by the user to gain access to a user ID, a file, a job variable, a network node, or an application.

pathname

A character string that is used to identify a file. A pathname consists of, at most, {PATH_MAX} bytes, including the terminating null byte. It has an optional beginning slash, followed by zero or more file names separated by slashes. If the pathname refers to a directory, it may also have one or more trailing slashes. Multiple successive slashes are considered to be the same as one slash. A pathname that begins with two successive slashes may be subject to special interpretation by some compatible implementations, although more than two leading slashes are treated as a single slash (see pathname resolution).

BS2000:
Every cataloged file in BS2000 can also be uniquely identified by a pathname. The pathname is composed of the catalog ID (catid), the user ID (userid), and a fully-qualified file name assigned by the user (e.g.: catid:$userid.filename).

pathname prefix

A pathname that begins with an optional slash and points to a directory.

pathname resolution

Pathname resolution is performed for a process to resolve a pathname to a particular file in a file hierarchy. There may be multiple pathnames that resolve to the same file.
Each file name in the pathname is located in the directory specified by its predecessor (for example, in the pathname fragment a/b, file b is located in directory a). Pathname resolution fails if this cannot be accomplished.
If the pathname begins with a slash, the predecessor of the first file name in the pathname is taken to be the root directory of the process. Such pathnames are referred to as absolute pathnames.
If the pathname does not begin with a slash, the predecessor of the first file name of the pathname is taken to be the current working directory of the process. Such pathnames are referred to as relative pathnames.
The interpretation of a pathname component is dependent on the values of {NAME_MAX} and {_POSIX_NO_TRUNC} associated with the path prefix of that component. If any pathname component is longer than {NAME_MAX}, and if {_POSIX_NO_TRUNC} is in effect for the path prefix of that component (see pathconf()), this is considered an error condition. Otherwise, only the first {NAME_MAX} bytes of the pathname component are taken into account. The special file name . (dot) refers to the directory specified by its predecessor. The special file name .. (dot-dot) refers to the parent directory of its predecessor. As a special case, in the root directory, dot-dot may refer to the root directory itself.
A pathname consisting of a single slash resolves to the root directory of the process. A null pathname is invalid.

pattern

A sequence of characters used either with regular expression notation or for pathname expansion as a means of selecting various character strings or pathnames, respectively. The syntaxes of the two patterns are similar, but not identical. This manual always indicates the type of pattern being referred to in the immediate context of the use of the term.

pipe

An object accessed by one of the pair of file descriptors created by the pipe() function. Once created, the file descriptors can be used to manipulate it, and it behaves identically to a FIFO special file when accessed in this way. It has no name in the file hierarchy.

portability

The capability of a program to run on different operating systems without changes. This is achieved by using standardized open programming interfaces that are offered on a variety of platforms.

portable character set

The collection of characters that are required to be present in all locales supported by XSI-conformant systems:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 ! # % ^ & * ( ) _ + - = { } [ ]
: "~ ; ́ , `, < > ? , . | \ / @ $

portable file name character set

For a file name to be portable across implementations conforming to the ISO POSIX-1 standard, it must consist only of the following characters:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 . _ -
The last three characters are the period, underscore and hyphen characters, respectively.
The hyphen must not be used as the first character of a portable file name. Uppercase and lowercase letters are differentiated by all conforming implementations.

In the case of a portable pathname, the slash character may also be used.

portable pathname

For a pathname to be portable across compatible systems, it should consist of at most {PATH_MAX} bytes, including the terminating null byte. It should be a pathname consisting of an optional leading slash, followed by zero or more portable file names separated by slashes.

POSIX file system

A file system in BS2000 with the structure of a UNIX file system (UFS). The POSIX file system comprises a set of directories and files (POSIX files) that are organized in a hierarchical tree structure. The root directory (/) is at the root of the tree, and all other directories are the branches from the root directory. Each file in the file system can be reached via precisely one absolute path and several conceivable relative paths.
The difference between a POSIX file system and a UNIX file system is the storage location: a UNIX file system is stored on a physical device, whereas a POSIX file system is stored in a PAM container file.

POSIX shell

A ported UNIX system program that handles communication between the user and the system. The POSIX shell is a command interpreter. It translates the entered POSIX commands into a language that can be processed by the system.
If the POSIX shell was entered as the "program" attribute of the user, the POSIX shell will be started automatically when the user logs on at a remote computer (rlogin).

process

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 by a call to the fork() function. The process that calls fork() is known as the parent process, and the new process created by the fork() is known as the child process.

process group

A collection of processes that permits the signalling of related processes. Each process in the system is a member of a process group that is identified by a process group ID. This grouping permits signals to be sent to related groups of processes. A newly created process joins the process group of its creator.

process group ID

The unique identifier representing a process group during its lifetime. A process group ID is a positive integer and cannot be reused by the system until the process group lifetime ends.

process group leader

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, due either to the end of the last process lifetime or to the last remaining process calling the setsid() or setpgid() functions.

process ID

A unique identifier of a process. A process ID is a positive integer that cannot be reused by the system until 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. Only a system process can have a process ID of 1.

process lifetime

The period of time that begins when a process is created and ends when its process ID is returned to the system.
After a process is created with a fork() 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(), or waitpid() function 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.

protocol

A set of rules for the exchange of data between two systems. The protocol defines the type of electrical connection, the data format, and the sequence of data.

pthread

A thread is a part of a program which runs concurrently with other parts. Several threads can run concurrently within a single process. A process must, however, comprise at least one thread. Unlike processes, all the threads of a program share a common address space.
In the case of the Pthreads in BS2000, the threads of a single process can be distributed over several tasks, unlike DCE threads, for instance.

radix character

The character that separates the integer part of a number from the fractional part.

read-only file system

A file system that has implementation-dependent characteristics restricting modifications.

real group ID

The attribute of a process that, at the time of process creation, identifies the group of the user who created the process (see group ID). This value is subject to change during the process lifetime, as described under setgid().

real user ID

The attribute of a process that, at the time of process creation, identifies the user who created the process (see user ID). This value is subject to change during the process lifetime, as described under setuid().

record-oriented I/O

BS2000:
Record-oriented I/O means that the file position indicator of the file can only be positioned at the start of a record or block. Record-oriented I/O enables efficient file processing, adapted to the structure of the BS2000 system. The unit for an I/O function call is always a record or block. Record-oriented processing can be used for cataloged SAM, ISAM and PAM files. Additional functions are available for actions such as deleting or inserting records or accessing keys in ISAM files.

regular expression

A pattern constructed according to specific rules (see section "Regular expressions" in the manual "POSIX Commands").

regular file

A file that is a randomly accessible sequence of bytes, with no further structure imposed by the system.

relative pathname

An access path for a file or directory, starting from the position of the current directory within the file system. Relative pathnames do not begin with a slash (/) (see pathname resolution).

remote machine

In a local network, a distinction is made between the local computer and the remote machines. As far as the user is concerned, all computers in the network other than the one at which he or she is directly working are remote machines. The user can communicate with all remote machines on the network.

root directory

A directory, associated with a process, that is used in pathname resolution for pathnames that begin with a slash.

saved set-group-ID

An attribute of a process that allows some flexibility in the assignment of the effective group ID attribute, as described under setgid() and exec.

saved set-user-ID

An attribute of a process that allows some flexibility in the assignment of the effective user ID attribute, as described under setuid() and exec.

security attributes

BS2000:
The attributes of an object (file, job variable, etc.) which define and control access to that object and are thus relevant to security.
For example, the following security attributes exist for files: ACCESS/USER-ACCESS, SERVICE bit, AUDIT attribute, RDPASS, WRPASS, EXPASS, RETPD, BACL, ACL and GUARD.

session

A collection of process groups established for job control purposes. 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()). Implementations that support setpgid() can have multiple process groups in the same session.

session leader

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

session lifetime

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

shell

A system program in UNIX that handles communication between the user and the system. The shell is a command interpreter. It translates the entered commands into a language that can be processed by the system. A shell is started for each user as soon as he or she has logged on to the system.

signal

A mechanism by which a process may be notified of, or affected by, an event occurring in the system. Examples of such events include hardware exceptions and specific actions by processes. The term signal is also used to refer to the event itself.

signal mask

The currently defined set of signals for a process that are to be blocked before the signal is delivered to that process. The signal mask of a process is initialized by its parent process. The signal mask can be controlled and manipulated with the sigaction(), sigfprocmask() and sigsuspend() functions.

slash

The term slash is used to represent the literal character /, also known as a sol idus.

special character

Characters that are assigned special functions on I/O (see section “General terminal interface” on page 130).

special file

A file, also called a device driver, that serves as the interface to an I/O device such as a terminal, disk drive, or line printer.

standard error

An output stream used for diagnostic messages.

standard input

A stream associated with a primary input device.

standard output

A stream associated with a primary output device.

standard utilities

The commands described in the manual "POSIX Commands" [2].

stream

A file access object that allows access to an ordered sequence of characters. Such objects can be created by the fdopen(), fopen() or popen() functions and are associated with a file descriptor. A stream provides the additional services of user-selectable buffering and formatted input and output.

stream-oriented I/O

Stream-oriented I/O means that the file position indicator can be positioned on each individual byte in the file. Stream I/O is the conventional processing mode and is set by default, i.e. without any special qualifiers specified for the open functions. Text files can be processed exclusively in this I/O mode. In contrast to record-oriented I/O, the data for output to files with stream I/O is first stored in an internal buffer and is written to the external file later (see buffering).

supplementary group ID

An attribute of a process used in determining file access permissions.
A process has up to {NGROUPS_MAX} supplementary group IDs 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. Whether a process ́ effective group ID is included in or omitted from its list of supplementary group IDs is unspecified.

suspended job

A background job that has received a SIGSTOP, SIGTSTP, SIGTTIN or SIGTTOU signal.

system

The term system is used in this manual to designate an implementation of the system interface.

system call

Request, from within a program, for a service that is executed by the operating system kernel.

system process

An object, other than a process executing an application, that is defined by the system and has a process ID.

system scheduling priority

A number used as advice to the system to alter process scheduling priorities. Raising the value gives the process additional preference when it is scheduled to run; lowering the value reduces the preference.

terminal

A character special file (i.e. a special file for a character-oriented device) that meets the specifications of the general terminal interface (see section “General terminal interface”).

text file

BS2000:
Text files are only possible for stream I/O. The following file types are treated as text files:

• cataloged SAM files (no binary mode on open),
• cataloged ISAM files,
• system files (SYSDTA, SYSOUT, SYSLST, SYSTERM)

A text file is an ordered sequence of bytes that are combined to form lines (or records). In contrast to binary files, the control characters for white space are converted to their appropriate effect, depending on the type of text file (see white space). This means that data read from a text file does not correspond precisely to the data that was originally written to it. Each written tab (\t) that is read is expanded to an appropriate number of spaces. The following points also apply to text files:

• Newline characters not originally written to the file may be read in (see fflush(), fseek(), fsetpos(), lseek(), rewind()).

• Output to SYSOUT and SYSTERM (for writing)
  Each line is started with a blank as a print control character. This produces a line feed.

• Output to SYSLST
  The line starts with a blank as the print control character only if none of the control characters \f, \v, \r or \b are specified in a line.

UNIX system

An operating system that works in interactive mode. UNIX was developed in 1969 by Bell Laboratories. Since only a central system kernel of this operating system is hardware-dependent, UNIX is installed on several different systems by various computer manufacturers. UNIX applications are portable to a large extent.

upshifting

The conversion of lowercase characters to their corresponding uppercase representations.

user

A representative of a user ID. The term user is used generically for people, applications, procedures, etc., that can obtain access to the operating system via a user ID.

user administration

BS2000:
All privileges that can be assigned with the command /SET-PRIVILEGE as well as the privileges of the security administrator and the system ID TSOS.

user attributes

All characteristics of a user ID that are stored in the join file (also called a user catalog).

user catalog

See join file.

user database

A system database of implementation-dependent format that contains at least the following information for each user ID:
user name, numerical user ID, initial numerical group ID, initial working directory, and initial user program.
The initial numerical group ID is used by the newgrp utility. Any other circumstances under which the initial values are made effective are implementationdependent.

user group

A collection of individual users under a single name (group ID).

user ID

A non-negative integer that is used to identify a system user. When the identity of a user is associated with a process, a user ID value is referred to as a real user ID, an effective user ID, or a saved set-user-ID.

user name

A string that is used to identify a user, as described in user database. To be portable across XSI-conformant systems, the value must be composed of characters from the portable file name character set. The hyphen should not be used as the first character of a portable user name.

user privileges

BS2000:
All attributes assigned to a user ID (login name), which are stored in the join file and which define the rights of the user.

variable

An object with a value that may change during program execution.

white space

A sequence of one or more characters that belong to the space character class as defined via the LC_CTYPE category in the current locale. In the POSIX locale, white space consists of one or more blank characters (space and tabs), newline characters, carriage-return characters, form-feed characters and horizontal or vertical tab characters.

wide character code

An integer value corresponding to a single graphic symbol or control code. All wide character codes of a process consist of the same number of bits. A wide character code for which all bits are set to zero is called a null wide character code.

wide character string

A contiguous sequence of wide character codes terminated by and including the first null wide character code.

zombie process

An inactive process that will be deleted at some later time when its parent process executes a wait() or waitpid() function.