Replace characters in a text file at a certain position
 

Hey guys!

i have a text file and want to write a textstring at, let's say, line 5 at position 4, and REPLACE the old text at that position with the new text-
so if line 5 looked like this:
ABCDEFGHIJKLMNOPQRSTUVWXYZ

Text to insert:
hello

pos 4:
ABCD>EFGHIJKLMNOPQRSTUVWXYZ

new line 5:
ABCDhelloJKLMNOPQRSTUVWXYZ

Can somebody tell me how to do this in bash, please?

Thank you!

Welcome to LQ!
Is this a homework? :)
You could try with sed.

As above, try with sed http://www.grymoire.com/Unix/Sed.html

You can do quite a bit (tediously) with commands such as tr, cut, join etc...

thanks everybody, couldn't get it to work the way i wanted to with sed, so i wrote a c program instead, using fopen etc. :)

I don't think there's a need to reinvent the wheel. As others said it can be done with sed

I'll post it as a little puzzle. Some basic sed knowledge is enough to solve it.


The string below needs to be reordered to replace the * bit in the sed command.

Example:

thank you, sycamorex

sed 4s/./hello/5 file

so this would work to replace the 5th letter in line 4, but literally only one letter is replaced
from:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
to:
ABCDhelloFGHIJKLMNOPQRSTUVWXYZ
instead of:
ABCDhelloJKLMNOPQRSTUVWXYZ

can you point me in the right direction to replace not only one letter and then insert the string, but to delete as many characters from the input file at that position as stringlength of "hello" is?

thx a ton!

Strictly speaking, the fifth occurrence of the pattern is replaced. Not merely symantic pedantry when more than one character is matched.Read the grymoire link above. Yes, all of it. You need to specify the length yourself.

Try the following:

The grymoire link will provide you with the knowledge to understand the above.