Shell Programming and Scripting

@anbu: As I see you are pretty conversant with the sed usage, I must let you know that I wouldnt have posted this question at all if I knew the way to write the sed code for my requirement , for which , I clearly quoted in my post requesting you to EXPLAIN what your POST is actually doing at the background. But somehow YOU MIGHT HAVE MISSED THAT POINT.

The positions 6 and 8 are just mere examples , but in real-time , I would be dealing with a file with volume in Gigs , for which I need to REPLACE ALL
CHARACTERS BETWEEN 103 and 108 POSITIONS (BOTH POSITIONS INCLUSIVE) OF EACH LINE WITH A STATIC STRING 00000000000000.


Thanks
Kumarjit.

@kumarjt
No rudeness please, keep in mind that contributor do it on their own time : this deserve a bit of respect : if the given example lack of clarification, you can just politely ask for some.

Code:

sed -n -e 's/\(.\{5\}\)...\(.*\)/\1KUMARJIT\2/p'

By the way, you may also read
http://pubs.opengroup.org/onlinepubs...ities/sed.html
and
http://pubs.opengroup.org/onlinepubs...html#tag_09_03

Thanks again ctsgnb .

But I fankly wasnt able to make out the meaning of the following line from quote.

Code:

\1 refers to what matched what was enclosed in the first \( \) 
\2 refers to what matched what was enclosed in the second \( \)

Request you to explain in simple terms ( if possible)

Thanks
Kumarjit.

Here is an exemple that - i hope - will help you to get the \( \) stuff

Code:

# echo "ABC" | sed 's/\(..\)\(.\)/\2-\1/'
C-AB

In fact it's like prenthesis ( ) but for them to be interpreted they need to be escaped with backslash
otherwise they are taken as litteral and not as an operator to delimit a matching string.

BTW Unix sed wants the ^ anchor outside the \( \):

Code:

echo 1234567890 | sed 's/\(^.....\).../\1KUMARJIT/'
1234567890
echo 1234567890 | sed 's/^\(.....\).../\1KUMARJIT/'
12345KUMARJIT90

and is IMHO better readable, too.
For the last requirement, it is

Code:

sed 's/^\(.\{102\}\).\{6\}/\100000000000000/'

.\{6\} is the same as ...... i.e. 6 times any character.
The \( \) marks the first 102 characters, followed by the next 6 characters. Trailing characters are not touched.
The entire match is substituted by \1 ie. the match of the first \( \), followed by 00000000000000.