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35 .\" @(#)join.1 8.3 (Berkeley) 4/28/95
43 .Nd relational database operator
47 .Fl a Ar file_number | Fl v Ar file_number
63 on the specified files
64 and writes the result to the standard output.
67 is the field in each file by which the files are compared.
68 The first field in each line is used by default.
69 There is one line in the output for each pair of lines in
73 which have identical join fields.
74 Each output line consists of the join field, the remaining fields from
76 and then the remaining fields from
79 The default field separators are tab and space characters.
80 In this case, multiple tabs and spaces count as a single field separator,
81 and leading tabs and spaces are ignored.
82 The default output field separator is a single space character.
84 Many of the options use file and field numbers.
85 Both file numbers and field numbers are 1 based, i.e., the first file on
86 the command line is file number 1 and the first field is field number 1.
87 The following options are available:
88 .Bl -tag -width indent
89 .It Fl a Ar file_number
90 In addition to the default output, produce a line for each unpairable
94 Replace empty output fields with
99 option specifies the fields that will be output from each file for
100 each line with matching join fields.
104 .Ar file_number . Ns Ar field ,
109 is a field number, or the form
112 representing the join field.
113 The elements of list must be either comma
115 or whitespace separated.
116 (The latter requires quoting to protect it from the shell, or, a simpler
117 approach is to use multiple
123 as a field delimiter for both input and output.
126 in a line is significant.
127 .It Fl v Ar file_number
128 Do not display the default output, but display a line for each unpairable
135 may be specified at the same time.
148 When the default field delimiter characters are used, the files to be joined
149 should be ordered in the collating sequence of
153 option, on the fields on which they are to be joined, otherwise
155 may not report all field matches.
156 When the field delimiter characters are specified by the
158 option, the collating sequence should be the same as
164 If one of the arguments
170 the standard input is used.
174 For compatibility with historic versions of
176 the following options are available:
177 .Bl -tag -width indent
179 In addition to the default output, produce a line for each unpairable line
202 Historical implementations of
204 permitted multiple arguments to the
207 These arguments were of the form
208 .Ar file_number . Ns Ar field_number
213 This has obvious difficulties in the presence of files named
217 These options are available only so historic shell scripts do not require
218 modification and should not be used.