join(1)
NAME
join − join files
SYNTAX
join [options] file1 file2
DESCRIPTION
The join command forms, on the standard output, a join of the two relations specified by the lines of file1 and file2. If file1 is ‘−’, the standard input is used.
The 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.
Fields are normally separated by blank, tab or new line. In this case, multiple separators count as one, and leading separators are discarded.
OPTIONS
−an
Produces an additional line for unpaired lines from specified file n, where n is 1 or 2.
−e s
Uses specified replacement string for all empty output fields. The −e option should be used with the −o option to specify fields that do not appear in a line.
−jn m
Joins the mth field in the nth file. If n is missing, use the mth field in each file.
−o list
Uses specified list for output line fields.
−tc
Sets tab character. Every appearance of c in a line is significant.
RESTRICTIONS
With default field separation, the collating sequence is that of sort −b; with −t, the sequence is that of a plain sort.