Manual page for JOIN(1)
join - relational database operator
SYNOPSIS
join
[
-an
] [
-e string
] [
-j
[1|2]
m
] [
-o list
] [
-tc
]
filename1
filename2
DESCRIPTION
join
forms, on the standard output, a join of the two relations specified
by the lines of
filename1
and
filename2.
If
filename1
is
`-',
the standard input is
used.
filename1
and
filename2
must be sorted in increasing
ASCII
collating sequence on the fields
on which they are to be joined -- normally the first in each line.
There is one line in the output for each pair of lines in
filename1
and
filename2
that have identical join fields. The output line normally consists of
the common field, then the rest of the line from
filename1,
then the rest of the line from
filename2.
The default input field separators are
SPACE,
TAB,
and
NEWLINE
characters.
If the default input field separators are used,
multiple separators count as one field separator,
and leading separators are ignored.
The default output field separator is a blank.
OPTIONS
- -an
-
The parameter
n
can be one of the values:
-
- 1
-
Produce a line for each unpairable line in
filename1.
- 2
-
Produce a line for each unpairable line in
filename2.
- 3
-
Produce a line for each unpairable line in both
filename1 and filename2.
The normal output is also produced.
- -e string
-
Replace empty output fields by
string.
- -j[1|2]m
-
The
j
may be immediately followed by
n,
which is either a
1
or a
2.
If
n
is missing, the join is on the
m'th
field of both files. If
n
is present, the join is on the
m'th
field of file
n,
and
the first field of the other. Note:
join
counts fields from 1 instead of 0 as
sort.1v
does.
- -o list
-
Each output line comprises the fields specified in
list,
each element of which has the form
n.m,
where
n
is a file number and
m
is a field number.
The common field is not printed unless specifically requested.
Note:
join
counts fields from 1 instead of 0 like
sort
does.
- -tc
-
Use character
c
as a separator (tab
character). Every appearance of
c
in a line is significant.
The character
c
is used as the field separator for both
input and output.
EXAMPLE
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.
join -j1 4 -j2 3 -o 1.1 2.1 1.6 -t: /etc/passwd /etc/group
SEE ALSO
awk.1
comm.1
look.1
sort.1v
uniq.1
BUGS
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
join,
sort,
comm,
uniq,
look,
and
awk
are wildly incongruous.
Filenames that are numeric may cause conflict
when the
-o
option is used right before listing filenames.
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97
