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 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 char-
     acters 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