join is a command in
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
and
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s that merges the lines of two sorted
text file
A text file (sometimes spelled textfile; an old alternative name is flatfile) is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists stored as data within a computer file system. In operat ...
s based on the presence of a common
field. It is similar to the join operator used in
relational database
A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relatio ...
s but operating on text files.
Overview
The
join command takes as input two text files and a number of options. If no
command-line argument
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
is given, this command looks for a pair of lines from the two files having the same first field (a sequence of characters that are different from space), and outputs a line composed of the first field followed by the rest of the two lines.
The program arguments specify which
character
Character or Characters may refer to:
Arts, entertainment, and media Literature
* ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk
* ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...
to be used in place of space to separate the fields of the line, which field to use when looking for matching lines, and whether to output lines that do not match. The output can be stored to another file rather than printing using
redirection.
As an example, the two following files list the known fathers and the mothers of some people. Both files have been sorted on the join field — this is a requirement of the program.
george jim
kumar gunaware
albert martha
george sophie
The join of these two files (with no argument) would produce:
george jim sophie
Indeed, only "george" is common as a first word of both files.
History
is intended to be a relation database operator. It is part of the
X/Open X/Open group (also known as the Open Group for Unix Systems and incorporated in 1987 as X/Open Company, Ltd.) was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of in ...
Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the
Single Unix Specification.
The version of
join bundled in
GNU
GNU () is an extensive collection of free software
Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any ...
coreutils
The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm, which are used on Unix-like operating systems.
In September 2002, the ''GNU coreutils'' were c ...
was written by Mike Haertel. The command is available as a separate package for
Microsoft Windows as part of the
UnxUtils
UnxUtils is a collection of ports of common GNU Unix-like utilities to native Win32, with executables only depending on the Microsoft C- runtime msvcrt.dll. The collection was last updated externally on April 15, 2003, by Karl M. Syring. ...
collection of
native
Native may refer to:
People
* Jus soli, citizenship by right of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Native Americans (disambiguation)
In arts and enterta ...
Win32
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations ...
ports of common GNU Unix-like utilities.
See also
*
Textutils
The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm, which are used on Unix-like operating systems.
In September 2002, the ''GNU coreutils'' were cr ...
*
Join (SQL)
A join clause in SQL – corresponding to a join operation in relational algebra – combines columns from one or more tables into a new table. Informally, a join stitches two tables and puts on the same row records with matching fields : INNER, ...
*
Relational algebra
In database theory, relational algebra is a theory that uses algebraic structures with a well-founded semantics for modeling data, and defining queries on it. The theory was introduced by Edgar F. Codd.
The main application of relational algebra ...
*
List of Unix commands
This is a list of Unix commands as specified by IEEE Std 1003.1-2008, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
List
See also
* List of G ...
References
External links
*
*
join command
Unix text processing utilities
Unix SUS2008 utilities
Plan 9 commands
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