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JOIN(1)                 NetBSD General Commands Manual                 JOIN(1)


NAME

     join -- relational database operator


SYNOPSIS

     join [-a file_number | -v file_number] [-e string] [-j file_number field]
          [-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.  (The argument to -a
                 must not be preceded by a space; see the COMPATIBILITY sec-
                 tion.)

     -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 ele-
                 ment of list has the form `file_number.field', where
                 file_number is a file number and field is a field number.
                 The elements of list must be either comma (``,'') or white-
                 space separated.  (The latter requires quoting to protect 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.

     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.  (To distinguish
                 between this and -a file_number, join currently requires that
                 the latter not include any white space.)

     -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 argu-
                 ments 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 shell scripts don't require
     modification and should not be used.


SEE ALSO

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


STANDARDS

     The join command is expected to be IEEE Std 1003.2 (``POSIX.2'') compati-
     ble.

NetBSD 5.0                      April 28, 1995                      NetBSD 5.0