NAME
join
- relational database operator
SYNOPSIS
join
ber | -v file_number
[-a file_num-]
[-e string]
[-j file_number field]
[-o list]
[-t char]
[-1 field]
[-2 field]
file1 file2
DESCRIPTION
The join utility performs an ``equality join'' on the specified files
and writes the result to the standard output.
The ``join field'' is the field in each file by which the files are compared.
The first field in each line is used by default.
There is one line in the output for each pair of lines in
file1
and
file2
which have identical join fields.
Each output line consists of the join field, the remaining fields from
file1
and then the remaining fields from
file2.
The default field separators are tab and space characters.
In this case, multiple tabs and spaces count as a single field separator,
and leading tabs and spaces are ignored.
The default output field separator is a single space character.
Many of the options use file and field numbers.
Both file numbers and field numbers are 1 based, i.e. the first file on
the command line is file number 1 and the first field is field number 1.
The following options are available:
- -a file_number
-
In addition to the default output, produce a line for each unpairable
line in file
file_number.
(The argument to
-a
must not be preceded by a space; see the
COMPATIBILITY
section.)
- -e string
-
Replace empty output fields with
string.
- -o list
-
The
-o
option specifies the fields that will be output from each file for
each line with matching join fields.
Each element of
list
has the form
`file_number.field',
where
file_number
is a file number and
field
is a field number.
The elements of list must be either comma (``,'') or whitespace separated.
(The latter requires quoting to protect it from the shell, or, a simpler
approach is to use multiple
-o
options.)
- -t char
-
Use character
char
as a field delimiter for both input and output.
Every occurrence of
char
in a line is significant.
- -v file_number
-
Do not display the default output, but display a line for each unpairable
line in file
file_number.
The options
-v 1
and
-v 2
may be specified at the same time.
- -1 field
-
Join on the
field'th
field of file 1.
- -2 field
-
Join on the
field'th
field of file 2.
When the default field delimiter characters are used, the files to be joined
should be ordered in the collating sequence of
sort(1),
using the
-b
option, on the fields on which they are to be joined, otherwise
join
may not report all field matches.
When the field delimiter characters are specified by the
-t
option, the collating sequence should be the same as
sort(1)
without the
-b
option.
If one of the arguments
file1
or
file2
is ``-'', the standard input is used.
The
join
utility exits 0 on success, and >0 if an error occurs.
COMPATIBILITY
For compatibility with historic versions of
,
the following options are available:
- -a
-
In addition to the default output, produce a line for each unpairable line
in both file 1 and file 2.
(To distinguish between this and
-a file_number,
join
currently requires that the latter not include any white space.)
- -j1 field
-
Join on the
field'th
field of file 1.
- -j2 field
-
Join on the
field'th
field of file 2.
- -j field
-
Join on the
field'th
field of both file 1 and file 2.
- -o list ...
-
Historical implementations of
join
permitted multiple arguments to the
-o
option.
These arguments were of the form ``file_number.field_number'' as described
for the current
-o
option.
This has obvious difficulties in the presence of files named ``1.2''.
These options are available only so historic shell scripts don't require
modification and should not be used.
SEE ALSO
awk(1),
comm(1),
paste(1),
sort(1),
uniq(1)
STANDARDS
The
join
command is expected to be
IEEE Std 1003.2 (``POSIX.2'')
compatible.