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

     join -- relational	database operator

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

     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 out-
     put 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 op-
     tions are available:

     -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
	     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

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

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

     -a	     In	addition to the	default	output,	produce	a line for each	un-
	     pairable 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	op-
	     tion.  This has obvious difficulties in the presence of files
	     named `1.2'.

     These options are available only so historic shellscripts don't require
     modification and should not be used.

     The join command conforms to IEEE Std 1003.1-2001 ("POSIX.1").

     awk(1), comm(1), paste(1),	sort(1), uniq(1)

BSD				 July 5, 2004				   BSD


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