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33.\"	@(#)join.1	8.3 (Berkeley) 4/28/95
34.\"
35.Dd April 28, 1995
36.Dt JOIN 1
37.Os
38.Sh NAME
39.Nm join
40.Nd relational database operator
41.Sh SYNOPSIS
42.Nm join
43.Oo
44.Fl a Ar file_number | Fl v Ar file_number
45.Oc
46.Op Fl e Ar string
47.Op Fl j Ar file_number field
48.Op Fl o Ar list
49.Bk -words
50.Ek
51.Op Fl t Ar char
52.Op Fl \&1 Ar field
53.Op Fl \&2 Ar field
54.Ar file1
55.Ar file2
56.Sh DESCRIPTION
57The
58.Nm
59utility performs an
60.Dq equality join
61on the specified files
62and writes the result to the standard output.
63The
64.Dq join field
65is the field in each file by which the files are compared.
66The first field in each line is used by default.
67There is one line in the output for each pair of lines in
68.Ar file1
69and
70.Ar file2
71which have identical join fields.
72Each output line consists of the join field, the remaining fields from
73.Ar file1
74and then the remaining fields from
75.Ar file2 .
76.Pp
77The default field separators are tab and space characters.
78In this case, multiple tabs and spaces count as a single field separator,
79and leading tabs and spaces are ignored.
80The default output field separator is a single space character.
81.Pp
82Many of the options use file and field numbers.
83Both file numbers and field numbers are 1 based, i.e., the first file on
84the command line is file number 1 and the first field is field number 1.
85.Pp
86The options are as follows:
87.Bl -tag -width Ds
88.It Fl a Ar file_number
89In addition to the default output, produce a line for each unpairable
90line in file
91.Ar file_number .
92.It Fl e Ar string
93Replace empty output fields with
94.Ar string .
95.It Fl o Ar list
96Specifies the fields that will be output from each file for
97each line with matching join fields.
98Each element of
99.Ar list
100has the form
101.Dq file_number.field ,
102where
103.Ar file_number
104is a file number and
105.Ar field
106is a field number,
107or the form
108.Dq 0
109(zero),
110representing the join field.
111The elements of list must be either comma
112.Pq Ql \&,
113or whitespace separated.
114(The latter requires quoting to protect it from the shell, or, a simpler
115approach is to use multiple
116.Fl o
117options.)
118.It Fl t Ar char
119Use character
120.Ar char
121as a field delimiter for both input and output.
122Every occurrence of
123.Ar char
124in a line is significant.
125.It Fl v Ar file_number
126Do not display the default output, but display a line for each unpairable
127line in file
128.Ar file_number .
129The options
130.Fl v Ar 1
131and
132.Fl v Ar 2
133may be specified at the same time.
134.It Fl 1 Ar field
135Join on the
136.Ar field Ns 'th
137field of file 1.
138.It Fl 2 Ar field
139Join on the
140.Ar field Ns 'th
141field of file 2.
142.El
143.Pp
144When the default field delimiter characters are used, the files to be joined
145should be ordered in the collating sequence of
146.Xr sort 1 ,
147using the
148.Fl b
149option, on the fields on which they are to be joined, otherwise
150.Nm
151may not report all field matches.
152When the field delimiter characters are specified by the
153.Fl t
154option, the collating sequence should be the same as
155.Xr sort 1
156without the
157.Fl b
158option.
159.Pp
160If one of the arguments
161.Ar file1
162or
163.Ar file2
164is
165.Dq - ,
166the standard input is used.
167.Pp
168The
169.Nm
170utility exits 0 on success or >0 if an error occurred.
171.Sh SEE ALSO
172.Xr awk 1 ,
173.Xr comm 1 ,
174.Xr paste 1 ,
175.Xr sort 1 ,
176.Xr uniq 1
177.Sh STANDARDS
178The
179.Nm
180command is expected to be
181.St -p1003.2
182compatible.
183.Pp
184In the absence of the
185.Fl o
186option,
187historical versions of
188.Nm
189wrote non-matching lines without reordering the fields.
190The current version writes the join field first, followed by the
191remaining fields.
192.Pp
193For compatibility with historical versions of
194.Nm join ,
195the following options are available:
196.Bl -tag -width Fl
197.It Fl a
198In addition to the default output, produce a line for each unpairable line
199in both file 1 and file 2.
200.It Fl j1 Ar field
201Join on the
202.Ar field Ns 'th
203field of file 1.
204.It Fl j2 Ar field
205Join on the
206.Ar field Ns 'th
207field of file 2.
208.It Fl j Ar field
209Join on the
210.Ar field Ns 'th
211field of both file 1 and file 2.
212.It Fl o Ar list ...
213Historical implementations of
214.Nm
215permitted multiple arguments to the
216.Fl o
217option.
218These arguments were of the form
219.Dq file_number.field_number
220as described for the current
221.Fl o
222option.
223This has obvious difficulties in the presence of files named
224.Dq 1.2 .
225.El
226.Pp
227These options are available only so historical shell scripts don't require
228modification and should not be used.
229.Sh HISTORY
230A
231.Nm
232utility appeared in
233.At v7 .
234