Replace string by regex

Question

I have bunch of string like "{one}two", where "{one}" could be different and "two" is always the same. I need to replace original sting with "three{one}", "three" is also constant. It could be easily done with python, for example, but I need it to be done with shell tools, like sed or awk.

Answer 1

If I understand correctly, you want:

{one}two --> three{one}
{two}two --> three{two}
{n}two   --> three{n}

SED with a backreference will do that:

echo "{one}two" | sed 's/\(.*\)two$/three\1/'

The search store all text up to your fixed string, and then replace with the your new string pre-appended to the stored text. SED is greedy by default, so it should grab all text up to your fixed string even if there's some repeat in the variable part (e.gxx`., {two}two will still remap to three{two} properly).

Answer 2

Using sed:

s="{one}two"
sed 's/^\(.*\)two/three\1/' <<< "$s"
three{one}

Answer 3

echo "XXXtwo" | sed -E 's/(.*)two/three\1/'

Answer 4

Here's a Bash only solution:

string="{one}two"
echo "three${string/two/}"

Answer 5

awk '{a=gensub(/(.*)two/,"three\\1","g"); print a}' <<< "{one}two"

Output:

three{one}

Answer 6

awk '/{.*}two/ { split($0,s,"}"); print "three"s[1]"}" }' <<< "{one}two"

does also output

three{one}

Here, we are using awk to find the correct lines, and then split on "}" (which means your lines should not contain more than the one to indicate the field).

Answer 7

Through GNU sed,

$ echo 'foo {one}two bar' | sed -r 's/(\{[^}]*\})two/three\1/g'
foo three{one} bar

Basic sed,

$ echo 'foo {one}two bar' | sed 's/\({[^}]*}\)two/three\1/g'
foo three{one} bar