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NAME    [Toc]    [Back]

     join - relational database operator

SYNOPSIS    [Toc]    [Back]

     join [-a file_number  |  -v  file_number]  [-e  string]  [-j
file_number field]
          [-o list] [-t char] [-1 field] [-2 field] file1 file2

DESCRIPTION    [Toc]    [Back]

     The join 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 options are as follows:

     -a file_number
             In addition to the default output,  produce  a  line
for each unpairable
 line in file file_number.

     -e string
             Replace empty output fields with string.

     -o list
             Specifies  the  fields that will be output from each
file for each
             line with matching join  fields.   Each  element  of
list has 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
 -o options.)

     -t char
             Use character char as a field delimiter for both input and output.
  Every occurrence of char in a line is significant.

     -v file_number
             Do not display the default  output,  but  display  a
line for each
             unpairable line in file file_number.  The options -v
1 and -v 2
             may be specified at the same time.

     -1 field
             Join on the field'th field of file 1.

     -2 field
             Join on the field'th field of file 2.

     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
     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

     The join utility exits 0 on success or >0 if  an  error  occurred.

SEE ALSO    [Toc]    [Back]

     awk(1), comm(1), paste(1), sort(1), uniq(1)

STANDARDS    [Toc]    [Back]

     The   join  command  is  expected  to  be  IEEE  Std  1003.2
(``POSIX.2'') compatible.

     In the absence of the -o option, historical versions of join
wrote nonmatching
  lines  without reordering the fields.  The current
version writes
     the join field first, followed by the remaining fields.

     For compatibility with historical versions of join, the following options
     are available:

     -a           In  addition  to  the default output, produce a
line for each
                 unpairable line in both file 1 and file 2.

     -j1 field   Join on the field'th field of file 1.

     -j2 field   Join on the field'th field of file 2.

     -j field    Join on the field'th field of both  file  1  and
file 2.

     -o list ...
                 Historical  implementations  of  join  permitted
multiple arguments
 to the -o option.  These arguments were of
the form
                 ``file_number.field_number''  as  described  for
the current -o
                 option.  This has obvious  difficulties  in  the
presence of
                 files named ``1.2''.

     These options are available only so historical shell scripts
don't require
 modification and should not be used.

HISTORY    [Toc]    [Back]

     A join utility appeared in Version 7 AT&T UNIX.

OpenBSD     3.6                          April      28,      1995
[ Back ]
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