join - relational database operator
join [-a file_number | -v file_number] [-e string] [-j
file_number field]
[-o list] [-t char] [-1 field] [-2 field] file1 file2
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 options are as follows:
-a file_number
In addition to the default output, produce a line
for each unpairable
line in file file_number.
-e string
Replace empty output fields with string.
-o list
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, or the form ``0'' (zero), representing
the join field. 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 or >0 if an error occurred.
awk(1), comm(1), paste(1), sort(1), uniq(1)
The join command is expected to be IEEE Std 1003.2
(``POSIX.2'') compatible.
In the absence of the -o option, historical versions of join
wrote nonmatching
lines without reordering the fields. The current
version writes
the join field first, followed by the remaining fields.
For compatibility with historical versions of join, 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.
-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 historical shell scripts
don't require
modification and should not be used.
A join utility appeared in Version 7 AT&T UNIX.
OpenBSD 3.6 April 28, 1995
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