How to insert word count as a string in a file?

I am trying to insert a line at the beginning of a file named text.txt that tells how many lines were in the text. Like:

After using the command, it should redirect the file into a textwc.txt, as

I tried to define a variable as a wc -l and tried to recall it into a awk, but i haven't achieve anything. Any ideas?

Solution

1st solution: Could you please try following in awk.

awk -v lines="$(wc -l < Input_file)" 'FNR==1{print lines} 1' Input_file

2nd solution: With 2 times reading Input_file try following.

awk 'FNR==NR{count++;next} FNR==1{print count} 1' Input_file Input_file

3rd solution: Using tac + awk solution.

tac Input_file | awk '1;END{print FNR}' | tac

4th solution: In case your Input_file is NOT huge then try following.

awk '{val=(val?val ORS:"")$0}  END{print FNR ORS val}' Input_file