| ||join - relational database operator
| ||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
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.
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.
- Join on the fieldnumberth
field of file 2. Fields are decimal integers starting with 1.
The following operands are supported:
- 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)).
for the description of the behavior of join when encountering
files greater than or equal to 2 Gbyte ( 231
| ||Example 1. Joining the password file and group file
Example 2. Using the o option
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
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:
where the large expanses of white space are meant to each
represent a single tab character), the command:
!Name Fax Number
Don +1 123-456-7899
Keith +1 456-789-0122
Yasushi +2 345-678-9011
example% join -t"tab" -a 1 -a 2 -e '(unknown)' -o 0,1.2,2.2 phone fax
!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
for descriptions of the following environment variables that affect the
execution of join: LC_CTYPE, LC_MESSAGES, LC_COLLATE, and NLSPATH.
The following exit values are returned:
- All input files were output successfully.
- An error occurred.
for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE
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.