NAME
join —
relational database operator
SYNOPSIS
join |
[-a file_number |
-v file_number]
[-e string]
[-o list]
[-t char]
[-1 field]
[-2 field]
file1 file2 |
DESCRIPTION
Thejoin utility performs an “equality
join” on the specified files and writes the result to the standard
output. The “join field” is the field in each file by which the
files are compared. The first field in each line is used by default. There is
one line in the output for each pair of lines in file1
and file2 which have identical join fields. Each output
line consists of the join field, the remaining fields from
file1 and then the remaining fields from
file2.
The default field separators are tab and space characters. In this case, multiple tabs and spaces count as a single field separator, and leading tabs and spaces are ignored. The default output field separator is a single space character.
Many of the options use file and field numbers. Both file numbers and field numbers are 1 based, i.e., the first file on the command line is file number 1 and the first field is field number 1. The following options are available:
-afile_number- In addition to the default output, produce a line for each unpairable line in file file_number.
-estring- Replace empty output fields with string.
-olist- The
-ooption specifies the fields that will be output from each file for each line with matching join fields. Each element of list has either the form file_number.field, where file_number is a file number and field is a field number, or the form ‘0’ (zero), representing the join field. The elements of list must be either comma (‘,’) or whitespace separated. (The latter requires quoting to protect it from the shell, or, a simpler approach is to use multiple-ooptions.) -tchar- Use character char as a field delimiter for both input and output. Every occurrence of char in a line is significant.
-vfile_number- Do not display the default output, but display a line for each unpairable
line in file file_number. The options
-v1and-v2may be specified at the same time. -1field- Join on the field'th field of file1.
-2field- Join on the field'th field of file2.
When the default field delimiter characters are used, the files to
be joined should be ordered in the collating sequence of
sort(1), using the -b option, on the fields
on which they are to be joined, otherwise join may
not report all field matches. When the field delimiter characters are
specified by the -t option, the collating sequence
should be the same as
sort(1) without the -b option.
If one of the arguments file1 or
file2 is ‘-’,
the standard input is used.
EXIT STATUS
The join utility exits 0 on
success, and >0 if an error occurs.
COMPATIBILITY
For compatibility with historic versions of
join, the following options are available:
-a- In addition to the default output, produce a line for each unpairable line in both file1 and file2.
-j1field- Join on the field'th field of file1.
-j2field- Join on the field'th field of file2.
-jfield- Join on the field'th field of both file1 and file2.
-olist ...- Historical implementations of
joinpermitted multiple arguments to the-ooption. These arguments were of the form file_number.field_number as described for the current-ooption. This has obvious difficulties in the presence of files named 1.2.
These options are available only so historic shell scripts do not require modification and should not be used.
SEE ALSO
STANDARDS
The join command conforms to
IEEE Std 1003.1-2001 (“POSIX.1”).