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| <tr><td width=20><td><b>JOIN(1)</b><td align=right><b>JOIN(1)</b> |
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| <p><font size=+1><b>NAME </b></font><br> |
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| join – relational database operator<br> |
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| <p><font size=+1><b>SYNOPSIS </b></font><br> |
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| <tt><font size=+1>join</font></tt> [ <i>options</i> ] <i>file1 file2<br> |
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| <p><font size=+1><b>DESCRIPTION </b></font><br> |
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| <i>Join</i> forms, on the standard output, a join of the two relations |
| specified by the lines of <i>file1</i> and <i>file2</i>. If one of the file |
| names is <tt><font size=+1>−</font></tt>, the standard input is used. |
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| <i>File1</i> and <i>file2</i> must be sorted in increasing ASCII collating sequence |
| on the fields on which they are to be joined, normally the first |
| in each line. |
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| There is one line in the output for each pair of lines in <i>file1</i> |
| and <i>file2</i> that have identical join fields. The output line normally |
| consists of the common field, then the rest of the line from <i>file1</i>, |
| then the rest of the line from <i>file2</i>. |
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| Input fields are normally separated spaces or tabs; output fields |
| by space. In this case, multiple separators count as one, and |
| leading separators are discarded. |
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| The following options are recognized, with POSIX syntax.<br> |
| <tt><font size=+1>−a</font></tt> <i>n</i> In addition to the normal output, produce a line for each |
| unpairable line in file <i>n</i>, where <i>n</i> is 1 or 2.<br> |
| <tt><font size=+1>−v</font></tt> <i>n</i> Like <tt><font size=+1>−a</font></tt>, omitting output for paired lines.<br> |
| <tt><font size=+1>−e</font></tt> <i>s</i> Replace empty output fields by string <i>s</i>.<br> |
| <tt><font size=+1>−1</font></tt> <i>m<br> |
| </i><tt><font size=+1>−2</font></tt> <i>m</i> Join on the <i>m</i>th field of <i>file1</i> or <i>file2</i>.<br> |
| <tt><font size=+1>−j</font></tt><i>n m<br> |
| </i> |
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| Archaic equivalent for <tt><font size=+1>−</font></tt><i>n</i> <tt><font size=+1>m</font></tt>.<br> |
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| <tt><font size=+1>−o</font></tt><i>fields<br> |
| </i> |
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| Each output line comprises the designated fields. The comma-separated |
| field designators are either <tt><font size=+1>0</font></tt>, meaning the join field, or have |
| the form <i>n</i>.<i>m</i>, where <i>n</i> is a file number and <i>m</i> is a field number. |
| Archaic usage allows separate arguments for field designators. |
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| </table> |
| <tt><font size=+1>−t</font></tt><i>c</i> Use character <i>c</i> as the only separator (tab character) on input |
| and output. Every appearance of <i>c</i> in a line is significant.<br> |
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| </table> |
| <p><font size=+1><b>EXAMPLES </b></font><br> |
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| <tt><font size=+1>sort /etc/passwd | join −t: −1 1 −a 1 −e "" − bdays<br> |
| </font></tt> |
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| Add birthdays to the <tt><font size=+1>/etc/passwd</font></tt> file, leaving unknown birthdays |
| empty. The layout of <tt><font size=+1>/adm/users</font></tt> is given in <a href="../man5/passwd.html"><i>passwd</i>(5)</a>; <tt><font size=+1>bdays</font></tt> contains |
| sorted lines like <tt><font size=+1>ken:Feb 4, 1953</font></tt>.<br> |
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| </table> |
| <tt><font size=+1>tr : ' ' </etc/passwd | sort −k 3 3 >temp<br> |
| join −1 3 −2 3 −o 1.1,2.1 temp temp | awk '$1 < $2'<br> |
| </font></tt> |
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| Print all pairs of users with identical userids.<br> |
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| <p><font size=+1><b>SOURCE </b></font><br> |
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| <tt><font size=+1>/usr/local/plan9/src/cmd/join.c<br> |
| </font></tt> |
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| <p><font size=+1><b>SEE ALSO </b></font><br> |
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| <a href="../man1/sort.html"><i>sort</i>(1)</a>, <a href="../man1/comm.html"><i>comm</i>(1)</a>, <a href="../man1/awk.html"><i>awk</i>(1)</a><br> |
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| </table> |
| <p><font size=+1><b>BUGS </b></font><br> |
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| With default field separation, the collating sequence is that |
| of <tt><font size=+1>sort −b −k</font></tt><i>y</i><tt><font size=+1>,</font></tt><i>y</i>; with <tt><font size=+1>−t</font></tt>, the sequence is that of <tt><font size=+1>sort −t</font></tt><i>x</i> <tt><font size=+1>−k</font></tt><i>y</i><tt><font size=+1>,</font></tt><i>y</i>. |
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| One of the files must be randomly accessible.<br> |
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