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33 .\" @(#)join.1 8.3 (Berkeley) 4/28/95
35 .Dd $Mdocdate: January 19 2014 $
40 .Nd relational database operator
46 .Fl a Ar file_number | Fl v Ar file_number
58 on the specified files
59 and writes the result to the standard output.
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
68 which have identical join fields.
69 Each output line consists of the join field, the remaining fields from
71 and then the remaining fields from
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.
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.
83 When the default field delimiter characters are used, the files to be joined
84 should be ordered in the collating sequence of
88 option, on the fields on which they are to be joined, otherwise
90 may not report all field matches.
91 When the field delimiter characters are specified by the
93 option, the collating sequence should be the same as
99 If one of the arguments
105 the standard input is used.
107 The options are as follows:
119 .It Fl a Ar file_number
120 In addition to the default output, produce a line for each unpairable
124 Replace empty output fields with
127 Specifies the fields that will be output from each file for
128 each line with matching join fields.
132 .Dq file_number.field ,
141 representing the join field.
142 The elements of list must be either comma
144 or whitespace separated.
145 (The latter requires quoting to protect it from the shell, or a simpler
146 approach is to use multiple
152 as a field delimiter for both input and output.
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
164 may be specified at the same time.
178 utility is compliant with the
182 In the absence of the
185 historical versions of
187 wrote non-matching lines without reordering the fields.
188 The current version writes the join field first, followed by the
191 For compatibility with historical versions of
193 the following options are available:
196 In addition to the default output, produce a line for each unpairable line
219 Historical implementations of
221 permitted multiple arguments to the
224 These arguments were of the form
225 .Dq file_number.field_number
226 as described for the current
229 This has obvious difficulties in the presence of files named
233 These options are available only so historical shell scripts don't require
234 modification and should not be used.