File: coreutils.info,  Node: Working with fields,  Next: Paired and unpaired lines,  Prev: Sorting files for join,  Up: join invocation

8.3.3 Working with fields
-------------------------

Use ‘-1’,‘-2’ to set the key fields for each of the input files.  Ensure
the preceding ‘sort’ commands operated on the same fields.

The following example joins two files, using the values from seventh
field of the first file and the third field of the second file:

     $ sort -k 7b,7 file1 > file1.sorted
     $ sort -k 3b,3 file2 > file2.sorted
     $ join -1 7 -2 3 file1.sorted file2.sorted > file3

If the field number is the same for both files, use ‘-j’:

     $ sort -k4b,4 file1 > file1.sorted
     $ sort -k4b,4 file2 > file2.sorted
     $ join -j4    file1.sorted file2.sorted > file3

Both ‘sort’ and ‘join’ operate of whitespace-delimited fields.  To
specify a different delimiter, use ‘-t’ in _both_:

     $ sort -t, -k3b,3 file1 > file1.sorted
     $ sort -t, -k3b,3 file2 > file2.sorted
     $ join -t, -j3    file1.sorted file2.sorted > file3

To specify a tab (ASCII 0x09) character instead of whitespace, use:(1)

     $ sort -t$'\t' -k3b,3 file1 > file1.sorted
     $ sort -t$'\t' -k3b,3 file2 > file2.sorted
     $ join -t$'\t' -j3    file1.sorted file2.sorted > file3

If ‘join -t ''’ is specified then the whole line is considered which
matches the default operation of sort:

     $ sort file1 > file1.sorted
     $ sort file2 > file2.sorted
     $ join -t '' file1.sorted file2.sorted > file3

   ---------- Footnotes ----------

   (1) the ‘$'\t'’ is supported in most modern shells.  For older
shells, use a literal tab.