| [9] | 1 | .\" @(#)join.1 6.1 (Berkeley) 4/29/85
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| 2 | .\"
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| 3 | .TH JOIN 1 "April 29, 1985"
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| 4 | .AT 3
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| 5 | .SH NAME
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| 6 | join \- relational database operator
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| 7 | .SH SYNOPSIS
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| 8 | .B join
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| 9 | .RB [ \-a\fIn ]
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| 10 | .RB [ \-e
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| 11 | .IR s ]
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| 12 | .RB [ \-o
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| 13 | .IR list ]
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| 14 | .RB [ \-t\fIc ]
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| 15 | file1 file2
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| 16 | .SH DESCRIPTION
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| 17 | .B Join
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| 18 | forms, on the standard output,
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| 19 | a join
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| 20 | of the two relations specified by the lines of
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| 21 | .I file1
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| 22 | and
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| 23 | .IR file2 .
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| 24 | If
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| 25 | .I file1
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| 26 | is `\-', the standard input is used.
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| 27 | .PP
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| 28 | .I File1
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| 29 | and
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| 30 | .I file2
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| 31 | must be sorted in increasing ASCII collating
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| 32 | sequence on the fields
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| 33 | on which they are to be joined,
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| 34 | normally the first in each line.
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| 35 | .PP
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| 36 | There is one line in the output
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| 37 | for each pair of lines in
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| 38 | .I file1
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| 39 | and
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| 40 | .I file2
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| 41 | that have identical join fields.
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| 42 | The output line normally consists of the common field,
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| 43 | then the rest of the line from
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| 44 | .IR file1 ,
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| 45 | then the rest of the line from
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| 46 | .IR file2 .
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| 47 | .PP
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| 48 | Fields are normally separated by blank, tab or newline.
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| 49 | In this case, multiple separators count as one, and
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| 50 | leading separators are discarded.
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| 51 | .PP
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| 52 | These options are recognized:
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| 53 | .TP
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| 54 | .BI \-a n
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| 55 | In addition to the normal output,
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| 56 | produce a line for each unpairable line in file
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| 57 | .IR n ,
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| 58 | where
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| 59 | .I n
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| 60 | is 1 or 2.
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| 61 | .TP
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| 62 | .BI \-e " s"
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| 63 | Replace empty output fields by string
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| 64 | .IR s .
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| 65 | .ig
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| 66 | .TP
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| 67 | .BI \-j "n m"
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| 68 | Join on the
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| 69 | .IR m th
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| 70 | field of file
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| 71 | .IR n .
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| 72 | If
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| 73 | .I n
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| 74 | is missing, use the
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| 75 | .IR m th
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| 76 | field in each file.
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| 77 | ..
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| 78 | .TP
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| 79 | .BI \-o " list"
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| 80 | Each output line comprises the fields specified in
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| 81 | .IR list ,
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| 82 | each element of which has the form
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| 83 | .IR n . m ,
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| 84 | where
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| 85 | .I n
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| 86 | is a file number and
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| 87 | .I m
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| 88 | is a field number.
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| 89 | .PP
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| 90 | .TP
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| 91 | .BI \-t c
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| 92 | Use character
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| 93 | .I c
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| 94 | as a separator (tab character).
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| 95 | Every appearance of
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| 96 | .I c
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| 97 | in a line is significant.
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| 98 | .SH "SEE ALSO"
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| 99 | .BR sort (1),
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| 100 | .BR comm (1),
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| 101 | .BR awk (9).
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| 102 | .SH BUGS
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| 103 | With default field separation,
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| 104 | the collating sequence is that of
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| 105 | .BR "sort \-b" ;
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| 106 | with
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| 107 | .BR \-t ,
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| 108 | the sequence is that of a plain sort.
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| 109 | .PP
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| 110 | The conventions of
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| 111 | .BR join ,
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| 112 | .BR sort ,
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| 113 | .BR comm ,
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| 114 | .BR uniq ,
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| 115 | .BR look
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| 116 | and
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| 117 | .BR awk (9)
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| 118 | are wildly incongruous.
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| 119 | .\" ref. to awk(9) man page corrected -- ASW 2005-01-15
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