join

JOIN(1)                      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 simpler approach is to use
             multiple -o options.)

     -t char
             Use character char as a field delimiter for both input and output.
             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”).

macOS 12.1                        July 5, 2004                        macOS 12.1