[SOLVED] Use sed to replace a single letter?

Spazztic_Killer · 12-01-2013, 11:59 AM

I cant seem to get sed to replace a single letter, when i use

Code:

sed -e 's/J/M/g'

It ends up matching more than a single letter of the data and replaces it to.

The data looks like

lastname:firstname:middlename

Quote:

Smith:James:J

it will look like

Quote:

Smith:Mames:M

Not sure how to confine sed to a single letter match?

druuna · 12-01-2013, 12:18 PM

The g makes it global (for all instances in the line). If you remove the g then only the first instance will be changed:

Code:

sed 's/J/M/'

You can change the second occurrence like this:

Code:

sed 's/J/M/2'

If the letter is the last on a line:

Code:

sed 's/J$/M/'

Shadow_7 · 12-01-2013, 12:46 PM

^ as above. The /g makes it do it multiple times for every instance in a line. Drop the g and it does the first instance only.

Madhu Desai · 12-01-2013, 11:45 PM

Quote:

Originally Posted by Spazztic_Killer

Not sure how to confine sed to a single letter match?

You can use word boundary (\< \> ot \b) to achieve it.

Code:

sed 's/\<J\>/M/g'
sed 's/\bJ\b/M/g'