UNIX for Dummies Questions & Answers

Hi all,

i have one file contains 20 records
1
2
-
-
-
20

i want to find 5th records and 8th records and 14th
plz tell me which command use?

Thanks to advance

Code:

sed -n '5p;8p;14p' file

if you are writing general programs you have two choices else the above answer is enough:

1. Scan the file sequentially to find your record.
2. Create a hash table as index for your file if it is very large:
key/value pairs in the hash is the record number and offset of that record in the file. when searching for an entry search in the hash table find the offset then seek to that offset directly. update the hash if you add new entries.

also there are other indexing mechanisms such as btree.

How can btree be used as an indexing mechanism? Good that different options are being explored, but for the question OP had asked, these data structures are too loaded and quite complex.

see here.. I was telling a general approach for this problem. of course for small applications there are better ways.