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33 .\" @(#)join.1 8.3 (Berkeley) 4/28/95
34 .\"
35 .Dd $Mdocdate: January 19 2014 $
36 .Dt JOIN 1
37 .Os
38 .Sh NAME
39 .Nm join
40 .Nd relational database operator
41 .Sh SYNOPSIS
42 .Nm join
43 .Op Fl 1 Ar field
44 .Op Fl 2 Ar field
45 .Oo
46 .Fl a Ar file_number | Fl v Ar file_number
47 .Oc
48 .Op Fl e Ar string
49 .Op Fl o Ar list
50 .Op Fl t Ar char
51 .Ar file1
52 .Ar file2
53 .Sh DESCRIPTION
54 The
55 .Nm
56 utility performs an
57 .Dq equality join
58 on the specified files
59 and writes the result to the standard output.
60 The
61 .Dq join field
62 is the field in each file by which the files are compared.
63 The first field in each line is used by default.
64 There is one line in the output for each pair of lines in
65 .Ar file1
66 and
67 .Ar file2
68 which have identical join fields.
69 Each output line consists of the join field, the remaining fields from
70 .Ar file1
71 and then the remaining fields from
72 .Ar file2 .
73 .Pp
74 The default field separators are tab and space characters.
75 In this case, multiple tabs and spaces count as a single field separator,
76 and leading tabs and spaces are ignored.
77 The default output field separator is a single space character.
78 .Pp
79 Many of the options use file and field numbers.
80 Both file numbers and field numbers are 1 based, i.e., the first file on
81 the command line is file number 1 and the first field is field number 1.
82 .Pp
83 When the default field delimiter characters are used, the files to be joined
84 should be ordered in the collating sequence of
85 .Xr sort 1 ,
86 using the
87 .Fl b
88 option, on the fields on which they are to be joined, otherwise
89 .Nm
90 may not report all field matches.
91 When the field delimiter characters are specified by the
92 .Fl t
93 option, the collating sequence should be the same as
94 .Xr sort 1
95 without the
96 .Fl b
97 option.
98 .Pp
99 If one of the arguments
100 .Ar file1
101 or
102 .Ar file2
103 is
104 .Sq - ,
105 the standard input is used.
106 .Pp
107 The options are as follows:
108 .Bl -tag -width Ds
109 .It Fl 1 Ar field
110 Join on the
111 .Ar field Ns 'th
112 field of
113 .Ar file1 .
114 .It Fl 2 Ar field
115 Join on the
116 .Ar field Ns 'th
117 field of
118 .Ar file2 .
119 .It Fl a Ar file_number
120 In addition to the default output, produce a line for each unpairable
121 line in file
122 .Ar file_number .
123 .It Fl e Ar string
124 Replace empty output fields with
125 .Ar string .
126 .It Fl o Ar list
127 Specifies the fields that will be output from each file for
128 each line with matching join fields.
129 Each element of
130 .Ar list
131 has the form
132 .Dq file_number.field ,
133 where
134 .Ar file_number
135 is a file number and
136 .Ar field
137 is a field number,
138 or the form
139 .Dq 0
140 (zero),
141 representing the join field.
142 The elements of list must be either comma
143 .Pq Ql \&,
144 or whitespace separated.
145 (The latter requires quoting to protect it from the shell, or a simpler
146 approach is to use multiple
147 .Fl o
148 options.)
149 .It Fl t Ar char
150 Use character
151 .Ar char
152 as a field delimiter for both input and output.
153 Every occurrence of
154 .Ar char
155 in a line is significant.
156 .It Fl v Ar file_number
157 Do not display the default output, but display a line for each unpairable
158 line in file
159 .Ar file_number .
160 The options
161 .Fl v Cm 1
162 and
163 .Fl v Cm 2
164 may be specified at the same time.
165 .El
166 .Sh EXIT STATUS
167 .Ex -std join
168 .Sh SEE ALSO
169 .Xr awk 1 ,
170 .Xr comm 1 ,
171 .Xr lam 1 ,
172 .Xr paste 1 ,
173 .Xr sort 1 ,
174 .Xr uniq 1
175 .Sh STANDARDS
176 The
177 .Nm
178 utility is compliant with the
179 .St -p1003.1-2008
180 specification.
181 .Pp
182 In the absence of the
183 .Fl o
184 option,
185 historical versions of
186 .Nm
187 wrote non-matching lines without reordering the fields.
188 The current version writes the join field first, followed by the
189 remaining fields.
190 .Pp
191 For compatibility with historical versions of
192 .Nm join ,
193 the following options are available:
194 .Bl -tag -width Fl
195 .It Fl a
196 In addition to the default output, produce a line for each unpairable line
197 in both
198 .Ar file1
199 and
200 .Ar file2 .
201 .It Fl j Ar field
202 Join on the
203 .Ar field Ns 'th
204 field of both
205 .Ar file1
206 and
207 .Ar file2 .
208 .It Fl j1 Ar field
209 Join on the
210 .Ar field Ns 'th
211 field of
212 .Ar file1 .
213 .It Fl j2 Ar field
214 Join on the
215 .Ar field Ns 'th
216 field of
217 .Ar file2 .
218 .It Fl o Ar list ...
219 Historical implementations of
220 .Nm
221 permitted multiple arguments to the
222 .Fl o
223 option.
224 These arguments were of the form
225 .Dq file_number.field_number
226 as described for the current
227 .Fl o
228 option.
229 This has obvious difficulties in the presence of files named
230 .Dq 1.2 .
231 .El
232 .Pp
233 These options are available only so historical shell scripts don't require
234 modification and should not be used.
235 .Sh HISTORY
236 A
237 .Nm
238 utility appeared in
239 .At v7 .