JOIN(1)                   BSD General Commands Manual                  JOIN(1)

NAME
     join -- relational database operator

SYNOPSIS
     join [-a file_number | -v file_number] [-e string] [-o list] [-t char]
          [-1 field] [-2 field] 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.  The following
     options are available:

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

     -e string
             Replace empty output fields with string.

     -o list
             The -o option specifies the fields that will be output from each
             file for each line with matching join fields.  Each element of
             list has the either the form `file_number.field', where
             file_number is a file number and field is a field number, or the
             form `0' (zero), representing 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 sim-
             pler approach is to use multiple -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.

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

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

     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.

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

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

     -a      In addition to the default output, produce a line for each
             unpairable line in both file 1 and file 2.

     -j1 field
             Join on the field'th field of file 1.

     -j2 field
             Join on the field'th field of file 2.

     -j field
             Join on the field'th field of both file 1 and file 2.

     -o list ...
             Historical implementations of join permitted multiple arguments
             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 historic shell scripts do not require
     modification.  They should not be used in new code.

LEGACY DESCRIPTION
     The -e option causes a specified string to be substituted into empty
     fields, even if they are in the middle of a line.  In legacy mode, the
     substitution only takes place at the end of a line.

     Only documented options are allowed.  In legacy mode, some obsolete
     options are re-written into current options.

     For more information about legacy mode, see compat(5).

SEE ALSO
     awk(1), comm(1), paste(1), sort(1), uniq(1), compat(5)

STANDARDS
     The join command conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD                              July 5, 2004                              BSD