upper- to lower-case using sed

Question

Hi, I'd like to change the following patterns:

getFoo_Bar

to:

getFoo_bar

(note the lower b)

Knowing neither foo nor bar, what is the replacement pattern?

I started writing

sed 's/\(get[A-Z][A-Za-z0-9]*_\)\([A-Z]\)/\1

but I'm stuck: I want to write "\2 lower case", how do I do that?

Maybe sed is not adapted?

Answer 1

From the FAQ: How do I convert a string to all lowercase or capital letters?

Answer 2

s/\(get[A-Z][A-Za-z0-9]*_\)\([A-Z]\)/\1\L\2/g

Test:

$ echo 'getFoo_Bar' | sed -e 's/\(get[A-Z][A-Za-z0-9]*_\)\([A-Z]\)/\1\L\2/g'
getFoo_bar

Answer 3

You can use perl for this one:

perl -pe 's/(get[A-Z][A-Za-z0-9]*)_([A-Z])/\1_\l\2/'

The \l is the trick here.

sed doesn't do upper/lowercase on matched groups.

Answer 4

Somewhat shorter:

echo getFoo_Bar | sed 's/_\(.\)/_\L\1/'

Answer 5

To change getFoo_Bar to getFoo_bar using sed :

echo "getFoo_Bar" | sed 's/^\(.\{7\}\)\(.\)\(.*\)$/\1\l\2\3/'

The upper and lowercase letters are handled by :

• \U Makes all text to the right uppercase.
• \u makes only the first character to the right uppercase.
• \L Makes all text to the right lowercase.
• \l Makes only the first character to the right lower case. (Note its a lowercase letter L)

The example is just one method for pattern matching, just based on modifying a single chunk of text. Using the example, getFoo_BAr transforms to getFoo_bAr, note the A was not altered.