join – relational database operator|
join [ options ] file1 file2|
Join forms, on the standard output, a join of the two relations
specified by the lines of file1 and file2. If one of the file
names is –, the standard input is used. |
File1 and file2 must be sorted in increasing ASCII collating sequence on the fields on which they are to be joined, normally the first in each line.
There is one line in the output for each pair of lines in file1 and file2 that have identical join fields. The output line normally consists of the common field, then the rest of the line from file1, then the rest of the line from file2.
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.
The following options are recognized, with POSIX syntax.
sort –t: +1 /adm/users | join –t: –1 2 –a 1 –e "" – bdays|
join –1 3 –2 3 –o 1.1,2.1 temp temp | awk '$1 < $2'
sort(1), comm(1), awk(1)|
With default field separation, the collating sequence is that
of sort –b –ky,y; with –t, the sequence is that of sort –tx –ky,y.
One of the files must be randomly accessible.