join

- relational database operator

Synopsis

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

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

Description

join performs an equality join on the files file1 and file2 and writes the resulting joined files to standard output. By default, a field is delimited by one or more spaces and tabs with leading spaces and/or tabs ignored. The -t option can be used to change the field delimiter.

The join field is a field in each file on which files are compared. By default join writes one line in the output for each pair of lines in files1 and files2 that have identical join fields. The default output line consists of the join field, then the remaining fields from file1, then the remaining fields from file2, but this can be changed with the -o option. 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 files file1 and file2 must be ordered in the collating sequence of sort -b on the fields on which they are to be joined otherwise the results are unspecified.

If either file1 or file2 is -, join uses standard input starting at the current location.

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 are output.

-e string

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

-j fieldnumber

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

-j1 fieldnumber

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

-j2 fieldnumber

Equivalent to -2 fieldnumber. 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 are 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 are output.

-1 fieldnumber

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

-2 fieldnumber

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

Operands

The following operands are supported:

file1

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.

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(5) for the description of the behavior of join when encountering files greater than or equal to 2 Gbyte (2³¹ bytes).

Examples

Example 1 Joining the password File and Group File

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 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(5) 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(5) for descriptions of the following attributes:

See Also

awk(1), comm(1), sort(1), uniq(1), attributes(5), environ(5), largefile(5), standards(5)

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.