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31 .\" @(#)join.1 8.3 (Berkeley) 4/28/95
39 .Nd relational database operator
43 .Fl a Ar file_number | Fl v Ar file_number
57 on the specified files
58 and writes the result to the standard output.
61 is the field in each file by which the files are compared.
62 The first field in each line is used by default.
63 There is one line in the output for each pair of lines in
67 which have identical join fields.
68 Each output line consists of the join field, the remaining fields from
70 and then the remaining fields from
73 The default field separators are tab and space characters.
74 In this case, multiple tabs and spaces count as a single field separator,
75 and leading tabs and spaces are ignored.
76 The default output field separator is a single space character.
78 Many of the options use file and field numbers.
79 Both file numbers and field numbers are 1 based, i.e., the first file on
80 the command line is file number 1 and the first field is field number 1.
81 The following options are available:
82 .Bl -tag -width indent
83 .It Fl a Ar file_number
84 In addition to the default output, produce a line for each unpairable
88 Replace empty output fields with
93 option specifies the fields that will be output from each file for
94 each line with matching join fields.
98 .Ar file_number . Ns Ar field ,
103 is a field number, or the form
106 representing the join field.
107 The elements of list must be either comma
109 or whitespace separated.
110 (The latter requires quoting to protect it from the shell, or, a simpler
111 approach is to use multiple
117 as a field delimiter for both input and output.
120 in a line is significant.
121 .It Fl v Ar file_number
122 Do not display the default output, but display a line for each unpairable
129 may be specified at the same time.
142 When the default field delimiter characters are used, the files to be joined
143 should be ordered in the collating sequence of
147 option, on the fields on which they are to be joined, otherwise
149 may not report all field matches.
150 When the field delimiter characters are specified by the
152 option, the collating sequence should be the same as
158 If one of the arguments
164 the standard input is used.
168 For compatibility with historic versions of
170 the following options are available:
171 .Bl -tag -width indent
173 In addition to the default output, produce a line for each unpairable line
196 Historical implementations of
198 permitted multiple arguments to the
201 These arguments were of the form
202 .Ar file_number . Ns Ar field_number
207 This has obvious difficulties in the presence of files named
211 These options are available only so historic shell scripts do not require
212 modification and should not be used.