fourth field is number in a line

Shell Programming and Scripting
1

hi
i hav a file like
121212 asdd d 7 dfsdffdffsdfsdfsdfdf rrretrtrtre
121212 asdd d 5 dfsdffdffsdfsdfsdfdf rrretrtrtre
121212 asdd d 5 dfsdffdffsdfsdfsdfdf rrretrtrtre
121212 asdd d 4 dfsdffdffsdfsdfsdfdf rrretrtrtre
121212 asdd d 6 dfsdffdffsdfsdfsdfdf rrretrtrtre

i need to extract lines if the 4th field contains the required no like 7
please help

2 
awk '$4==7' file > new.file
3

hi
try this

awk '$4 == 7 { printf "%s\n",$0; }' filename

4

hi danmero
is is working but when i gave
awk '$4==$threadno' file > new.file is not working
it is creating a empty file,please help

5 
awk '$4=='$threadno'' file > new.file