join(C)                         19 June 1992                         join(C)


 Name

    join - join two relations

 Syntax

    join [ options ] file1 file2

 Description

    The join command prints to the standard output a join of the two rela-
    tions specified by the lines of file1 and file2.  If file1 is a dash (-),
    the standard input is used.

    file1 and file2 must be sorted in increasing collating sequence (defined
    by the current locale; see locale(M)) 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.

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

    These options are recognized:

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

    -e s      Replaces empty output fields by string s.

    -j nm     Joins on the mth field of file n.  If n is missing, uses the
              mth field in each file.

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

    -t c      Uses character c as a field separator.  Every appearance of c
              in a line is significant.

 See also

    awk(C), comm(C), sort(C)

 Notes

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

 Standards conformance

    join is conformant with:

    AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.