How to truncate the lines to specific length in a file which occurs between specific patterns?

Question

I have a file in which I have to truncate only the lines which comes between pattern @TEST and enabled="true">. When there is a match, the string between @TEST and enabled="true"> should be only 50 characters. All other lines should be left intact.

Example 1:

@TEST-TC_234 @TEST My name is Elli,I like to Travel, my hobbies are reading books,cooking,listening to music.I have a dog and the dog is black in colour  enabled="true">

I have to change above line as shown below.

@TEST-TC_234 @TEST My name is Elli,I like to Travel, my hobbies are r enabled="true">

Also I have few sentences containing special characters which needs to be truncated as above

Example

@TEST 05030508227_${mode} @TEST 2 Framed ABCSubData (ABCupdateLoc) with abcdcsmelSubscriptionInfo parameter  populated by tub and ABC DOS data, when ABCDN DOS & xyzabcdeDOS both use  E.164 rule where the Restriction is '4-restrict via ABC DOS'" enabled="true">

I have to change above line as shown below.

Answer 1

awk to the rescue!

$ awk '{if(match($0,/@TEST .*enabled="true">$/))
          {bo=length("@TEST");
           eo=length("enabled=\"true\">"); 
           len=(RLENGTH-bo-eo)>50?50:RLENGTH-bo-eo; 
           print substr($0,0,RSTART+bo+len) substr($0,length($0)-eo)}
       else print}' file

split the line for begin/end pattern if there is match; truncate the mid section and put them back together. If there is no match print unmodified lines.

For the updated example, the above script yields

@TEST 05030508227_${mode} @TEST 2 Framed ABCSubData (ABCupdateLoc) with abcdcsme enabled="true">