According a book published by Dr Malwinder Jit Singh Waraich, Bhagat Singh wrote the following lines in Gurmukhi in his diary in 1929, while in Jail.
Main Ghareebon Kaa Dil Hoon Watan Kee Zubaan
Main to Gaataa Chaloon Saath
Main To Badhtaa Chaloon
Now You Know!