The output of seek is used by the replace and append programs to write new rows and by lock and unlock to set and remove row locks.

-fc

use c (instead of TAB) as the input column separation character.

-m[bhirs]

use fast access methods. See search.

-o outfile

write the row found in outfile.

$ cat inventory
Item    Amount  Cost    Value   Description
----    ------  ----    -----   --------------
   1         3    50      150   rubber gloves
   2       100     5      500   test tubes
   3         5    80      400   clamps
   4        23    19      437   plates
   5        99    24     2376   cleaning cloth
   6        89   147    13083   bunsen burners
   7         5   175      875   scales

$ echo 5 | seek -mb inventory Item
207     245     0       8

The numbers mean that the row is 207 bytes from the beginning of the file and that it ends at byte 245 (making it 38 bytes long).

The following commands extract a row, blank it out, and then write it back into the inventory in the same place as the original row.

$ LOCATION=`echo 5 | seek -mb -o tmp inventory Item`
$ cat tmp
Item    Amount  Cost    Value   Description
----    ------  ----    -----   --------------
   5        99    24     2376   cleaning cloth

$ blank < tmp | replace inventory $LOCATION
$ cat inventory
Item    Amount  Cost    Value   Description
----    ------  ----    -----   --------------
   1         3    50      150   rubber gloves
   2       100     5      500   test tubes
   3         5    80      400   clamps
   4        23    19      437   plates
 
   6        89   147    13083   bunsen burners
   7         5   175      875   scales