tcsh error: while loop - while-loop

Question

This is a basic program but since I'm a newbie, I'm not able to figure out the solution.
I have a file named rama.xvg in the following format:
-75.635 105.879 ASN-2
-153.704 64.7089 ARG-3
-148.238 -47.6076 GLN-4
-63.2568 -8.05441 LEU-5
-97.8149 -7.34302 GLU-6
-119.276 8.99017 ARG-7
-144.198 -103.917 SER-8
-65.4354 -10.3962 GLY-9
-60.6926 12.424 ARG-10
-159.797 -0.551989 PHE-11
65.9924 -48.8993 GLY-12
179.677 -7.93138 GLY-13
..........
...........
-70.5046 38.0408 GLY-146
-155.876 153.746 TRP-147
-132.355 151.023 GLY-148
-66.2679 167.798 ASN-2
-151.342 -33.0647 ARG-3
-146.483 41.3483 GLN-4
..........
..........
-108.566 0.0212432 SER-139
47.6854 33.6991 MET-140
47.9466 40.1073 ASP-141
46.4783 48.5301 SER-142
-139.17 172.486 LYS-143
58.9514 32.0602 SER-144
60.744 18.3059 SER-145
-94.0533 165.745 GLY-146
-161.809 177.435 TRP-147
129.172 -101.736 GLY-148
I need to extract all the lines containing "ASN-2" in one file all_1.dat and so on for all the 147 residues.
If I run the following command in the terminal, it gives the desired output for ASN-2:
awk '{if( NR%147 == 1 ) printf $0 "\n"}' rama.xvg > all_1.dat
To avoid doing it repeatedly for all the residues, I have written the following code.
#!/bin/tcsh
set i = 1
while ( $i < 148)
echo $i
awk '{if( NR%147 == i ) printf $0 "\n"}' rama.xvg > all_"$i".dat
# i++
end
But this code prints the lines containing GLY-148 in all the output files.
Please let me know what is the error in this code. I think it is related to nesting.

Answer 1

In your awk-line the variable i is an awk-variable not shell variable! If you want use shell-variable $i you can do:
awk -v i="$i" '{if( NR%147 == i ) printf $0 "\n"}' rama.xvg > all_"$i".dat
But I think would better put your while-loop into awk:
awk '{for (i=1; i<=147; i++) { if (NR%147==i) {printf $0 "\n" > ("all_" i ".dat") } } }' rama.xvg