How to replace a fixed position character of a string?

Akash Mondal 0
Viewed 62

Suppose I have a file having a string AKASHMANDAL

I want to replace 7th positioned character (whatever the character may be) with "D"

Output will looks like

AKASHMDNDAL

I tried with the following command which only add the character after 7th position

sed -E 's/^(.{7})/\1D/' file

This gives me AKASHMADNDAL

How can I replace the character instead of just adding?

sed
4 Answers

Substitute any character in the 7th position using sed

$ sed 's/./D/7' input_file
AKASHMDNDAL
HatLess0

You can simply match one character outside of the capture group:

sed  -E 's/^(.{6})./\1D/'

(notice the dot outside the parenthesis)

Simon Doppler0

If you can consider an awk solution. awk can handle it better without regex and with more power to tweak based on positions:

awk '{print substr($0,1,6) "D" substr($0,8)}' file

AKASHMDNDAL
anubhava0

With your shown samples only, please try following awk code. Written and tested in GNU awk. Here is the Online demo for used awk code here.

awk -v RS='^.{7}' '
RT{
  sub(/.$/,"",RT)
  ORS=RT"D"
  print
}
END{
  ORS=""
  print
}
' Input_file
RavinderSingh130
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