JOIN(1)JOIN(1)NAMEjoin - relational database operator
SYNOPSISjoin [-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 rela‐
tions 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 con‐
sists 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 collat‐
ing 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(5) 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(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:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│CSI │ Enabled │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
└────────────────────┴─────────────────┘
SEE ALSOawk(1), comm(1), sort(1), uniq(1), attributes(5), environ(5), large‐
file(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.
Feb 8, 2000 JOIN(1)
