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JOIN(1) 		     General Commands Manual			 JOIN(1)

NAME
     join - relational database operator

SYNOPSIS
     join [ options ] file1 file2

DESCRIPTION
     Join  forms,  on the standard output, a join of the two relations specified
     by the lines of file1 and file2.  If one of the file names is the	standard
     input is used.

     File1  and  file2	must be sorted in increasing ASCII collating sequence on
     the fields on which they are to be joined, normally the first in each line.

     There is one line in the output for each pair of lines in file1  and  file2
     that  have identical join fields.	The output line normally consists of the
     common field, then the rest of the line from file1, then the  rest  of  the
     line from file2.

     Input fields are normally separated spaces or tabs; output fields by space.
     In  this case, multiple separators count as one, and leading separators are
     discarded.

     The following options are recognized, with POSIX syntax.

     -a n   In addition to the normal output, produce a line for each unpairable
	    line in file n, where n is 1 or 2.

     -v n   Like -a, omitting output for paired lines.

     -e s   Replace empty output fields by string s.

     -1 m
     -2 m   Join on the mth field of file1 or file2.

     -jn m  Archaic equivalent for -n m.

     -ofields
	    Each output line comprises the designated fields.	The  comma-sepa-
	    rated  field  designators  are  either 0, meaning the join field, or
	    have the form n.m, where n is a file number and m is a field number.
	    Archaic usage allows separate arguments for field designators.

     -tc    Use character c as the only separator (tab character) on  input  and
	    output.  Every appearance of c in a line is significant.

EXAMPLES
     sort /etc/passwd | join -t: -1 1 -a 1 -e "" - bdays
	    Add  birthdays  to	the  /etc/passwd file, leaving unknown birthdays
	    empty.  The layout of /adm/users is given in passwd((5)); bdays con-
	    tains sorted lines like

     tr : ' ' </etc/passwd | sort -k 3 3 >temp
     join -1 3 -2 3 -o 1.1,2.1 temp temp | awk '$1 < $2'
	    Print all pairs of users with identical userids.

SOURCE
     /src/cmd/join.c

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

BUGS
     With default field separation, the collating sequence is that  of	sort  -b
     -ky,y; with -t, the sequence is that of sort -tx -ky,y.

     One of the files must be randomly accessible.

									 JOIN(1)

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