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
file1
or
file2
is
-,
the standard input is used.
file1
and
file2
must be sorted in increasing collating sequence
(see Environment Variables below)
on the fields on which they are to be joined;
normally the first in each line.
The output contains one line for each pair of lines in
file1
and
file2
that have identical join fields.
The output line normally consists of the common field
followed by the rest of the line from
file1,
then the rest of the line from
file2.
The default input field separators are space, tab, or new-line.
In this case, multiple separators count as one field separator,
and leading separators are ignored.
The default output field separator is a space.
Some of the below options use the argument
n.
This argument should be a
1
or a
2
referring to either
file1
or
file2,
respectively.
Options
- -a n
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.
- -j m
Join on field
m
of both files.
The argument
m
must be delimited by space characters.
This option and the following two are provided for backward compatibility.
Use of the
-1
and
-2
options ( see below ) is recommended for portability.
- -j1 m
Join on field
m
of
file1.
- -j2 m
Join on field
m
of
file2.
- -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.
The common field is not printed unless specifically requested.
- -t c
Use character
c
as a separator (tab character).
Every appearance of
c
in a line is significant.
The character
c
is used as the field separator for both input and output.
- -v file_number
Instead of the default output,
produce a line only for each unpairable line in
file_number,
where
file_number
is
1
or
2.
- -1 f
Join on field
f
of file 1.
Fields are numbered starting with 1.
- -2 f
Join on field
f
of file 2.
Fields are numbered starting with 1.
EXTERNAL INFLUENCES
Environment Variables
LC_COLLATE
determines the collating sequence
join
expects from input files.
LC_CTYPE
determines the alternative blank character as an input field separator,
and the interpretation of data within files
as single and/or multi-byte characters.
LC_CTYPE
also determines whether the separator defined through the
-t
option is a single- or multi-byte character.
If
LC_COLLATE
or
LC_CTYPE
is not specified in the environment
or is set to the empty string, the value of
LANG
is used as a default for each unspecified or empty variable.
If
LANG
is not specified or is set to the empty string, a default of ``C'' (see
lang(5))
is used instead of
LANG.
If any internationalization variable contains an invalid setting,
join
behaves as if all internationalization variables are set to ``C''
(see
environ(5)).
International Code Set Support
Single- and multi-byte character code sets are supported
with the exception that multi-byte-character file names are not supported.
EXAMPLES
The following command line joins the password file and the group file,
matching on the numeric group
ID,
and outputting the login name, the group name,
and the login directory.
It is assumed that the files have been sorted
in the collating sequence defined by the
LC_COLLATE
or
LANG
environment variable on the group
ID
fields.
join -1 4 -2 3 -o 1.1 2.1 1.6 -t: /etc/passwd /etc/group
The following command produces an output consisting all possible combinations
of lines that have identical first fields in the two sorted files
sf1
and
sf2,
with each line consisting of the first and third fields from
sorted_file1
and the second and fourth fields from
sorted_file2:
join -j1 1 -j2 1 -o 1.1,2.2,1.3,2.4 sorted_file1 sorted_file2
WARNINGS
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,
and
awk
are incongruous.
Numeric filenames may cause conflict when the
-o
option is used immediately before listing filenames.
AUTHOR
join
was developed by OSF and HP.
STANDARDS CONFORMANCE
join: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2
Printable version
