Write a script to put a series of files in sequence - bash

Question

I am beginning in scripting and I am trying to write a script in bash. I need a script to write a sequence of several file names that are numbered from 1 to 50 inside one file. These are trajectory files from MD simulations. My idea was to write something like:
for valor in {1..50}
do
echo "
#!/bin/bash
catdcd -o Traj-all.dcd -stride 10 -dcd traj-$valor.dcd" > Traj.bash
exit
However, I just got one file with the following line:
#!/bin/bash
catdcd -o Traj-all.dcd -stride 10 -dcd traj-50.dcd
exit
But what I really want is something like:
#!/bin/bash
catdcd -o Traj-all.dcd -stride 10 -dcd traj-1.dcd -dcd traj-2.dcd -dcd traj-3.dcd ... -dcd traj-50.dcd
exit
How can I solve this problem?

Answer 1

You need to read a bit more about bash brace expansion. You can do this:
{
echo "#!/bin/bash"
echo "catdcd -o Traj-all.dcd -stride 10" "-dec traj-"{1..50}".dcd"
# ^^^^^^^^^^^^^^^^^^^^^^^^^
} > Traj.bash
The underlined part is where the brace expansion will get expanded by the shell into
-dec traj-1.dcd -dec traj-2.dcd ... -dec traj-50.dcd
You don't need to explicitly end your script with exit -- the shell will exit by itself when it runs out of commands.

Answer 2

> truncates the file on open. Either only use it once before the loop to create the file and then append (>>) within the loop, or redirect the entire loop.
> foo
for ...
do ...
echo ... >> foo
done
...
{
for ...
do ...
echo ...
done
} > foo