NAME

join − relational database operator

SYNOPSIS

join [ options ] file1 file2

DESCRIPTION

Join forms, on the standard output, is a join of the two relations specified by the lines of file1 and file2. If file1 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, which is normally the first field in each line. 

One line in the output exists for each pair of lines in file1 and file2 that have identical join fields.  The output line normally consists of the common field, and the remainder of the line from file1, and file2.

Fields are normally separated by blank, tab or newline.  In this case, multiple separators count as one, and leading separators are discarded. 

The following options are recognized:

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

−e s Replace empty output fields by string s.

−jn m
Join on the mth field of file n. If n is missing, use the mth field in each file.

−o list
Each output line comprises the fields specifed in list, of which each element has the form n.m, where n is a file number and m is a field number. 

−tc Use character c as a separator (tab character).  Every appearance of c in a line is significant. 

SEE ALSO

sort(1), comm(1), awk(1)

BUGS

With default field separation, the collating sequence is that of sort −b; with −t, the sequence is that of a plain sort. 

The conventions of join, sort, comm, uniq, look and awk(1) are wildly incongruous.

October 26, 1983  —  %W%%Q%%Y%