Rename files in a directory the simplest way in a script - unix

Question

I want to write a script that add '0' at the end of the files that doesn't have it.
This is what I wrote:
#!/bin/bash
for file in $1
do
echo $file
ls $file | grep "\0$"
if ["$?"="1"]
then
fi
done
I don't know hot to target the files in a way I can rename them

Answer 1

for file in *[!0]; do mv "$file" "${file}0"; done
For each name that does not end 0, rename it so it does. Note that this handles names with spaces etc in them.
I want to give the script a directory, and it will rename the files in it that do not end in 0. How can I use this in a way I can tell the script which directory to work with?
So, make the trivial necessary changes, working with a single directory (and not rejecting the command line if more than one directory is specified; just quietly ignoring the extras):
for file in "${1:?}"/*[!0]; do mv "$file" "${file}0"; done
The "${1:?}" notation ensures that $1 is set and is not empty, generating an error message if it isn't. You could alternatively write "${1:-.}" instead; that would work on the current directory instead of a remote directory. The glob then generates the list of file names in that directory that do not end with a 0 and renames them so that they do. If you have Bash, you can use shopt -s nullglob you won't run into problems if there are no files without the 0 suffix in the directory.
You can generalize to handle any number of arguments (all supposed to be directories, defaulting to the current directory if no directory is specified):
for dir in "${#:-.}"
do
for file in "$dir"/*[!0]; do mv "$file" "${file}0"; done
done
Or (forcing directories):
for dir in "${#:-.}"
do
(cd "$dir" && for file in *[!0]; do mv "$file" "${file}0"; done)
done
This has the merit of reporting which arguments are not directories, or are inaccessible directories.
There are endless variations of this sort that could be made; some of them might even be useful.
Now, I want to do the same but, instead of the file ending with '0', the script should rename files that do not end with '.0' so that they do end with '.0'?
This is slightly trickier because of the revised ending. Simply using [!.][!0] is insufficient. For example, if the list of files includes 30, x.0, x0, z.9, and z1, then echo *[!.][!0] only lists z1 (omitting 30, x0 and z.9 which do not end with .0).
I'd probably use something like this instead:
for dir in "${#:-.}"
do
(
cd "$dir" &&
for file in *
do
case "$file" in
(*.0) : skip it;;
(*) mv "$file" "${file}0";;
esac
done
)
done
The other alternative lists more glob patterns:
for dir in "${#:-.}"
do
(cd "$dir" && for file in *[!.][!0] *.[!0] *[!.]0; do mv "$file" "${file}0"; done)
done
Note that this rapidly gets a lot trickier if you want to look for files not ending .00 — there would be a 7 glob expressions (but the case variant would work equally straight-forwardly), and shopt -s nullglob becomes increasingly important (or you need [ -f "$file" ] && mv "$file" "${file}.0" instead of the simpler move command).