JOIN(1) BSD Reference Manual JOIN(1)NAMEjoin - relational database operator
SYNOPSISjoin [-a file_number | -v file_number] [-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 sin-
gle 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 un-
pairable 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 whi-
tespace separated. (The latter requires quoting to protect it
from the shell, or, a simpler approach is to use multiple -o op-
tions.)
-t char
Use character char as a field delimiter for both input and out-
put. 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.
SEE ALSOawk(1), comm(1), paste(1), sort(1), uniq(1)STANDARDS
The join command is expected to be IEEE Std 1003.2 ("POSIX.2") compati-
ble.
In the absence of the -o option, historical versions of join wrote non-
matching 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 argu-
ments 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 re-
quire modification and should not be used.
HISTORY
A join utility appeared in Version 7 AT&T UNIX.
MirOS BSD #10-current April 28, 1995 1
