JOIN(1)                    OpenBSD Reference Manual                    JOIN(1)

NAME
     join - relational database operator

SYNOPSIS
     join [-1 field] [-2 field] [-a file_number | -v file_number] [-e string]
          [-o list] [-t char] file1 file2

DESCRIPTION
     The join utility performs an ``equality join'' on the specified files and
     writes the result to the standard output.  The ``join field'' is the
     field in each file by which the files are compared.  The first field in
     each line is used by default.  There is one line in the output for each
     pair of lines in file1 and file2 which have identical join fields.  Each
     output line consists of the join field, the remaining fields from file1
     and then the remaining fields from file2.

     The default field separators are tab and space characters.  In this case,
     multiple tabs and spaces count as a single field separator, and leading
     tabs and spaces are ignored.  The default output field separator is a
     single space character.

     Many of the options use file and field numbers.  Both file numbers and
     field numbers are 1 based, i.e., the first file on the command line is
     file number 1 and the first field is field number 1.

     When the default field delimiter characters are used, the files to be
     joined should be ordered in the collating sequence of sort(1), using the
     -b option, on the fields on which they are to be joined, otherwise join
     may not report all field matches.  When the field delimiter characters
     are specified by the -t option, the collating sequence should be the same
     as sort(1) without the -b option.

     If one of the arguments file1 or file2 is `-', the standard input is
     used.

     The options are as follows:

     -1 field
             Join on the field'th field of file1.

     -2 field
             Join on the field'th field of file2.

     -a file_number
             In addition to the default output, produce a line for each un-
             pairable line in file file_number.

     -e string
             Replace empty output fields with string.

     -o list
             Specifies the fields that will be output from each file for each
             line with matching join fields.  Each element of list has the
             form ``file_number.field'', where file_number is a file number
             and field is a field number, or the form ``0'' (zero), represent-
             ing the join field.  The elements of list must be either comma
             (`,') or whitespace separated.  (The latter requires quoting to
             protect it from the shell, or a simpler approach is to use multi-
             ple -o options.)

     -t char
             Use character char as a field delimiter for both input and out-
             put.  Every occurrence of char in a line is significant.

     -v file_number
             Do not display the default output, but display a line for each
             unpairable line in file file_number.  The options -v 1 and -v 2
             may be specified at the same time.

     The join utility exits 0 on success, and >0 if an error occurs.

SEE ALSO
     awk(1), comm(1), lam(1), paste(1), sort(1), uniq(1)

STANDARDS
     The join utility is compliant with the IEEE Std 1003.1-2008 (``POSIX'')
     specification.

     In the absence of the -o option, historical versions of join wrote non-
     matching lines without reordering the fields.  The current version writes
     the join field first, followed by the remaining fields.

     For compatibility with historical versions of join, the following options
     are available:

     -a          In addition to the default output, produce a line for each
                 unpairable line in both file1 and file2.

     -j field    Join on the field'th field of both file1 and file2.

     -j1 field   Join on the field'th field of file1.

     -j2 field   Join on the field'th field of file2.

     -o list ...
                 Historical implementations of join permitted multiple argu-
                 ments to the -o option.  These arguments were of the form
                 ``file_number.field_number'' as described for the current -o
                 option.  This has obvious difficulties in the presence of
                 files named ``1.2''.

     These options are available only so historical shell scripts don't re-
     quire modification and should not be used.

HISTORY
     A join utility appeared in Version 7 AT&T UNIX.

OpenBSD 4.7                    February 8, 2009                              2
