join is a command in

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user 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

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operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s that merges the lines of two sorted

text file A text file (sometimes spelled textfile; an old alternative name is flat file) 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 ope ...

s based on the presence of a common field. It is similar to the join operator used in

relational database A relational database (RDB) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A Relational Database Management System (RDBMS) is a type of database management system that stores data in a structured for ...

s but operating on text files.

Overview

The join command takes as input two text files and several options. If no command-line argument 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 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 printed 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 Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the

Single Unix Specification The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, ...

. The version of join bundled in GNU coreutils was written by Mike Haertel. The command is available as a separate package for

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as part of the UnxUtils collection of native Win32

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of common GNU Unix-like utilities.

References

External links

* *
join command
{{Core Utilities commands Unix text processing utilities Unix SUS2008 utilities Plan 9 commands

Overview

History

See also

References

External links