|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
JOIN(1P) POSIX Programmer's Manual JOIN(1P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
join — relational database operator
join [−a file_number|−v file_number] [−e string] [−o list] [−t char]
[−1 field] [−2 field] file1 file2
The join utility shall perform an equality join on the files file1
and file2. The joined files shall be written to the standard output.
The join field is a field in each file on which the files are
compared. The join utility shall write one line in the output for
each pair of lines in file1 and file2 that have identical join
fields. The output line by default shall consist of the join field,
then the remaining fields from file1, then the remaining fields from
file2. This format can be changed by using the −o option (see
below). The −a option can be used to add unmatched lines to the
output. The −v option can be used to output only unmatched lines.
The files file1 and file2 shall be ordered in the collating sequence
of sort −b on the fields on which they shall be joined, by default
the first in each line. All selected output shall be written in the
same collating sequence.
The default input field separators shall be <blank> characters. In
this case, multiple separators shall count as one field separator,
and leading separators shall be ignored. The default output field
separator shall be a <space>.
The field separator and collating sequence can be changed by using
the −t option (see below).
If the same key appears more than once in either file, all
combinations of the set of remaining fields in file1 and the set of
remaining fields in file2 are output in the order of the lines
encountered.
If the input files are not in the appropriate collating sequence, the
results are unspecified.
The join utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
−a file_number
Produce a line for each unpairable line in file
file_number, where file_number is 1 or 2, in addition to
the default output. If both −a1 and −a2 are specified, all
unpairable lines shall be output.
−e string Replace empty output fields in the list selected by −o with
the string string.
−o list Construct the output line to comprise the fields specified
in list, each element of which shall have one of the
following two forms:
1. file_number.field, where file_number is a file number
and field is a decimal integer field number
2. 0 (zero), representing the join field
The elements of list shall be either <comma>-separated or
<blank>-separated, as specified in Guideline 8 of the Base
Definitions volume of POSIX.1‐2008, Section 12.2, Utility
Syntax Guidelines. The fields specified by list shall be
written for all selected output lines. Fields selected by
list that do not appear in the input shall be treated as
empty output fields. (See the −e option.) Only specifically
requested fields shall be written. The application shall
ensure that list is a single command line argument.
−t char Use character char as a separator, for both input and
output. Every appearance of char in a line shall be
significant. When this option is specified, the collating
sequence shall be the same as sort without the −b option.
−v file_number
Instead of the default output, produce a line only for each
unpairable line in file_number, where file_number is 1 or
2. If both −v1 and −v2 are specified, all unpairable lines
shall be output.
−1 field Join on the fieldth field of file 1. Fields are decimal
integers starting with 1.
−2 field Join on the fieldth field of file 2. Fields are decimal
integers starting with 1.
The following operands shall be supported:
file1, file2
A pathname of a file to be joined. If either of the file1
or file2 operands is '−', the standard input shall be used
in its place.
The standard input shall be used only if the file1 or file2 operand
is '−'. See the INPUT FILES section.
The input files shall be text files.
The following environment variables shall affect the execution of
join:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions
volume of POSIX.1‐2008, Section 8.2, Internationalization
Variables for the precedence of internationalization
variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_COLLATE
Determine the locale of the collating sequence join expects
to have been used when the input files were sorted.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte
as opposed to multi-byte characters in arguments and input
files).
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
Default.
The join utility output shall be a concatenation of selected
character fields. When the −o option is not specified, the output
shall be:
"%s%s%s\n", <join field>, <other file1 fields>,
<other file2 fields>
If the join field is not the first field in a file, the
<other file fields> for that file shall be:
<fields preceding join field>, <fields following join field>
When the −o option is specified, the output format shall be:
"%s\n", <concatenation of fields>
where the concatenation of fields is described by the −o option,
above.
For either format, each field (except the last) shall be written with
its trailing separator character. If the separator is the default
(<blank> characters), a single <space> shall be written after each
field (except the last).
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 All input files were output successfully.
>0 An error occurred.
Default.
The following sections are informative.
Pathnames consisting of numeric digits or of the form string.string
should not be specified directly following the −o list.
The −o 0 field essentially selects the union of the join fields. For
example, given file phone:
!Name Phone Number
Don +1 123-456-7890
Hal +1 234-567-8901
Yasushi +2 345-678-9012
and file fax:
!Name Fax Number
Don +1 123-456-7899
Keith +1 456-789-0122
Yasushi +2 345-678-9011
(where the large expanses of white space are meant to each represent
a single <tab>), the command:
join −t "<tab>" −a 1 −a 2 −e '(unknown)' −o 0,1.2,2.2 phone fax
would produce:
!Name Phone Number Fax Number
Don +1 123-456-7890 +1 123-456-7899
Hal +1 234-567-8901 (unknown)
Keith (unknown) +1 456-789-0122
Yasushi +2 345-678-9012 +2 345-678-9011
Multiple instances of the same key will produce combinatorial
results. The following:
fa:
a x
a y
a z
fb:
a p
will produce:
a x p
a y p
a z p
And the following:
fa:
a b c
a d e
fb:
a w x
a y z
a o p
will produce:
a b c w x
a b c y z
a b c o p
a d e w x
a d e y z
a d e o p
The −e option is only effective when used with −o because, unless
specific fields are identified using −o, join is not aware of what
fields might be empty. The exception to this is the join field, but
identifying an empty join field with the −e string is not historical
practice and some scripts might break if this were changed.
The 0 field in the −o list was adopted from the Tenth Edition version
of join to satisfy international objections that the join in the base
documents does not support the ``full join'' or ``outer join''
described in relational database literature. Although it has been
possible to include a join field in the output (by default, or by
field number using −o), the join field could not be included for an
unpaired line selected by −a. The −o 0 field essentially selects the
union of the join fields.
This sort of outer join was not possible with the join commands in
the base documents. The −o 0 field was chosen because it is an
upwards-compatible change for applications. An alternative was
considered: have the join field represent the union of the fields in
the files (where they are identical for matched lines, and one or
both are null for unmatched lines). This was not adopted because it
would break some historical applications.
The ability to specify file2 as − is not historical practice; it was
added for completeness.
The −v option is not historical practice, but was considered
necessary because it permitted the writing of only those lines that
do not match on the join field, as opposed to the −a option, which
prints both lines that do and do not match. This additional facility
is parallel with the −v option of grep.
Some historical implementations have been encountered where a blank
line in one of the input files was considered to be the end of the
file; the description in this volume of POSIX.1‐2008 does not cite
this as an allowable case.
Earlier versions of this standard allowed −j, −j1, −j2 options, and a
form of the −o option that allowed the list option-argument to be
multiple arguments. These forms are no longer specified by
POSIX.1‐2008 but may be present in some implementations.
None.
awk(1p), comm(1p), sort(1p), uniq(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 JOIN(1P)
Pages that refer to this page: sort(1p)