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)