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OpenDarwin 7.2.1 - man page for join (opendarwin section 1)

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 pro-
	     tect 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.

DIAGNOSTICS
     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 shellscripts don't require modification and
     should not be used.

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

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

BSD					  April 18, 2002				      BSD


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