TH JOIN 1
CT 1 files
SH NAME
join \- relational database operator
SH SYNOPSIS
B join
[
I options
]
I file1 file2
SH DESCRIPTION
I Join
forms, on the standard output,
a join
of the two relations specified by the lines of
I file1
and
IR file2 .
If one of the file names is
LR - ,
the standard input is used.
PP
I File1
and
I file2
must be sorted in increasing
SM ASCII
collating
sequence on the fields
on which they are to be joined,
normally the first in each line.
PP
There is one line in the output
for each pair of lines in
I file1
and
I file2
that have identical join fields.
The output line normally consists of the common field,
then the rest of the line from
IR file1 ,
then the rest of the line from
IR file2 .
PP
Input fields are normally separated spaces or tabs;
output fields by space.
In this case, multiple separators count as one, and
leading separators are discarded.
PP
The following options are recognized, with POSIX syntax.
TP
BI -a " n
In addition to the normal output,
produce a line for each unpairable line in file
IR n ,
where
I n
is 1 or 2.
TP
BI -v " n
Like
BR -a ,
omitting output for paired lines.
TP
BI -e " s
Replace empty output fields by string
IR s .
TP
BI -1 " m
br
ns
TP
BI -2 " m
Join on the
IR m th
field of
I file1
or
IR file2 .
TP
BI -j "n m"
Archaic equivalent for
BI - n " m"\f1.
TP
BI -o fields
Each output line comprises the designated fields.
The comma-separated field designators are either
BR 0 ,
meaning the join field, or have the form
IR n . m ,
where
I n
is a file number and
I m
is a field number.
Archaic usage allows separate arguments for field designators.
PP
TP
BI -t c
Use character
I c
as the only separator (tab character) on input and output.
Every appearance of
I c
in a line is significant.
SH EXAMPLES
TP
L
sort -t: +1 /adm/users | join -t: -1 2 -a 1 -e "" - bdays
Add birthdays to the
B /adm/users
file, leaving unknown
birthdays empty.
The layout of
B /adm/users
is given in
IR users (6);
B bdays
contains sorted lines like
LR "ken:Feb\ 4,\ 1953" .
TP
L
tr : ' ' </adm/users | sort -k 3 3 >temp
br
ns
TP
L
join -1 3 -2 3 -o 1.1,2.1 temp temp | awk '$1 < $2'
Print all pairs of users with identical userids.
SH SOURCE
B /sys/src/cmd/join.c
SH "SEE ALSO"
IR sort (1),
IR comm (1),
IR awk (1)
SH BUGS
With default field separation,
the collating sequence is that of
BI "sort -b"
BI -k y , y\f1;
with
BR -t ,
the sequence is that of
BI "sort -t" x
BI -k y , y\f1.
br
One of the files must be randomly accessible.
