JOIN(1) User Commands JOIN(1)

NAME

join - relational database operator

SYNOPSIS

join [-a filenumber | -v filenumber] [-1 fieldnumber]
[-2 fieldnumber] [-o list] [-e string] [-t char] file1 file2


join [-a filenumber] [-j fieldnumber] [-j1 fieldnumber]
[-j2 fieldnumber] [-o list] [-e string] [-t char] file1 file2

DESCRIPTION

The join command forms, on the standard output, a join of the two
relations specified by the lines of file1 and file2.


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. This format can be changed by
using the -o option (see below). The -a option can be used to add
unmatched lines to the output. The -v option can be used to output
only unmatched lines.


The default input field separators are blank, 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 blank.


If the input files are not in the appropriate collating sequence, the
results are unspecified.

OPTIONS

Some of the options below use the argument filenumber. This argument
should be a 1 or a 2 referring to either file1 or file2,
respectively.

-a filenumber
In addition to the normal output, produce a line
for each unpairable line in file filenumber,
where filenumber is 1 or 2. If both -a 1 and -a 2
are specified, all unpairable lines will be
output.


-e string
Replace empty output fields in the list selected
by option -o with the string string.


-j fieldnumber
Equivalent to -1fieldnumber -2fieldnumber.


-j1 fieldnumber
Equivalent to -1fieldnumber.


-j2 fieldnumber
Equivalent to -2fieldnumber. Fields are numbered
starting with 1.


-o list
Each output line includes the fields specified in
list. Fields selected by list that do not appear
in the input will be treated as empty output
fields. (See the -e option.) Each element of
which has the either the form
filenumber.fieldnumber, or 0, which represents
the join field. The common field is not printed
unless specifically requested.


-t char
Use character char as a separator. Every
appearance of char in a line is significant. The
character char is used as the field separator for
both input and output. With this option
specified, the collating term should be the same
as sort without the -b option.


-v filenumber
Instead of the default output, produce a line
only for each unpairable line in filenumber,
where filenumber is 1 or 2. If both -v 1 and -v 2
are specified, all unpairable lines will be
output.


-1 fieldnumber
Join on the fieldnumberth field of file 1. Fields
are decimal integers starting with 1.


-2fieldnumber
Join on the fieldnumberth field of file 2. Fields
are decimal integers starting with 1.

OPERANDS

The following operands are supported:

file1


file2
A path name of a file to be joined. If either of the file1
or file2 operands is -, the standard input is used in its
place.


file1 and file2 must be sorted in increasing collating sequence as
determined by LC_COLLATE on the fields on which they are to be
joined, normally the first in each line (see sort(1)).

USAGE

See largefile(7) for the description of the behavior of join when
encountering files greater than or equal to 2 Gbyte (2^31 bytes).

EXAMPLES

Example 1: Joining the password file and group file

The following command line will join 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 ASCII collating sequence on the group ID
fields.


example% join -j1 4-j2 3 -o 1.1 2.1 1.6 -t:/etc/passwd /etc/group

Example 2: Using the -o option

The -o 0 field essentially selects the union of the join fields. For
example, given file phone:


!Name Phone Number
Don +1 123-456-7890
Hal +1 234-567-8901
Yasushi +2 345-678-9012


and file fax:


!Name Fax Number

Don +1 123-456-7899

Keith +1 456-789-0122

Yasushi +2 345-678-9011


where the large expanses of white space are meant to each represent a
single tab character), the command:


example% join -t"tab" -a 1 -a 2 -e '(unknown)' -o 0,1.2,2.2 phone fax


would produce


!Name Phone Number Fax Number
Don +1 123-456-7890 +1 123-456-7899
Hal +1 234-567-8901 (unknown
Keith (unknown) +1 456-789-012
Yasushi +2 345-678-9012 +2 345-678-9011

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment
variables that affect the execution of join: LANG, LC_ALL, LC_CTYPE,
LC_MESSAGES, LC_COLLATE, and NLSPATH.

EXIT STATUS

The following exit values are returned:

0
All input files were output successfully.


>0
An error occurred.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|CSI | Enabled |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO

awk(1), comm(1), sort(1), uniq(1), attributes(7), environ(7),
largefile(7), standards(7)

NOTES

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 the join, sort, comm, uniq, and awk commands are
wildly incongruous.

February 8, 2000 JOIN(1)