NAME

join − join lines of two files on a common field

SYNOPSIS

join [−a 1|2] [−v 1|2] [−e empty-string] [−o field-list...] [−t char] [−j[1|2] field] [−1 field] [−2 field] file1 file2
join {−−help,−−version}

DESCRIPTION

This manual page documents the GNU version of join.  join prints to the standard output a line for each pair of input lines, one each from file1 and file2, that have identical join fields.  Either filename (but not both) can be ‘−’, meaning the standard input. file1 and file2 should be already sorted in increasing order (not numerically) on the join fields; unless the −t option is given, they should be sorted ignoring blanks at the start of the line, as sort does when given the −b option. 

The defaults are: the join field is the first field in each line; fields in the input are separated by one or more blanks, with leading blanks on the line ignored; fields in the output are separated by a space; each output line consists of the join field, the remaining fields from file1, then the remaining fields from file2.

OPTIONS

−a file-number
Print a line for each unpairable line in file file-number (either 1 or 2), in addition to the normal output. 

−e string
Replace empty output fields (those that are missing in the input) with string.

−1, −j1 field
Join on field field (a positive integer) of file 1. 

−2, −j2 field
Join on field field (a positive integer) of file 2. 

−j field
Equivalent to −1 field −2 field.

−o field-list... 
Construct each output line according to the format in field-list. Each element in field-list consists of a file number (either 1 or 2), a period, and a field number (a positive integer).  The elements in the list are separated by commas or blanks.  Multiple field-list arguments can be given after a single −o option; the values of all lists given with −o are concatenated together. 

−t char
Use character char as the input and output field separator. 

−v file-number
Print a line for each unpairable line in file file-number (either 1 or 2), instead of the normal output. 

In addition, when GNU join is invoked with exactly one argument, the following options are recognized:

−−help
Print a usage message on standard output and exit successfully.

−−version
Print version information on standard output then exit successfully.