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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.

     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)

FreeBSD 5.4			 July 5, 2004			   FreeBSD 5.4

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