ruby - Replacing text from a file with regular expressions -

i'm trying read xml file , substitute dp sp everywhere in text textsize attribute used. example android:textsize="8dp" replaced android:textsize="8sp" if below file processed:

<?xml version="1.0" encoding="utf-8"?> <linearlayout                xmlns:android="http://schemas.android.com/apk/res/android"               android:layout_width="fill_parent"               android:layout_height="wrap_content" >      <textview             android:id="@+id/description"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:textsize="8dp"/>      <view                         android:layout_width="wrap_content"             android:layout_height="5dp" />  </linearlayout> 

and have following code:

patterndp = /android:textsize=\"[\d]+dp\"/ content = file.read("layout/some_layout.xml") content.gsub!(patterndp, "???") 

i know second parameter of gsub! method string replace pattern, , have difficulties on how use in such way method not replace whole android:textsize="8dp" sp, dp string pattern.

would appreciate help, if approach not correct please let me know how solve problem in way.

capture digit(\d+) , use \\1 in replacement obtain capture.

input = input.gsub(/(?<=android:textsize=")(\d+)dp"/, '\\1sp"') 

(?<=android:textsize=") checking whether digits after android:textsize=" text or not doesn't pick others.

however, if not wish use lookbehind (?<=...) simple one.

input = input.gsub(/android:textsize="(\d+)dp"/, 'android:textsize="\\1sp"')