Shell Programming and Scripting

Hi,
can I do something like this to add a condition of checking if the 4th field is number or space or blank also:

awk -F, '$4 /^[]*||[0-9]*/' MYFILE >> OTHERFILE

I also want the other part i.e. I need to exclude all lines whose 4th field is space or blank or number:

MYFILE
a,b,c,d,e
a,b,c,2,r
c,d,f,,g
t,y,u, ,i

The new file should contain only first line. I tried using the below but I also get 3rd line

awk -F, '$4 /^ [A-Z]*/' MYFILE >> OTHERFILE

I need OTHERFILE to have only first record.

this will work .. but its not the efficient code

Code:

 
awk -F, '$4 !~ /^[0-9]/  && $4 !~ /^[ ]/ && $4!=""' filename

What about:

Code:

awk -F, '$4 ~/^[a-zA-Z]/' file