Bash - Automating creation of test files

Question

I'm in the process of understanding shell scripting - this is my simple code for adding test files for python unittest

I'm looking for best practice pointers, variable naming, and of course comments on structure and readability.

EDIT: Script is called by, for example

./create_tests.sh math tensor_add

dir_name="1ドル"
file_name="2ドル"
test_dir="test/${dir_name}"
file_in_dir="${test_dir}/${file_name}.py"
addFile() {
 if [[ -f "${file_in_dir}" ]]
 then
 echo "File already exists in directory, exiting."
 exit 0
 else
 touch "${file_in_dir}"
 fi
}
if [[ -d "${test_dir}" ]]
then
 echo "Directory already exists, adding the file to this directory."
 addFile
else
 echo "Directory and __init__.py created."
 mkdir "${test_dir}"
 touch "${test_dir}/__init__.py"
 addFile
fi

Answer 1

1. Add a shebang.
2. Keep naming consistent, I personally prefer and follow Google's style guide; you may use a different guide if available.
3. Try to make your script POSIX compliant, for a wider target reach (no need to rely on [[ expression from bash)
4. Define a function to create the test directory.
5. Use shellcheck.
6. The echo "Directory and __init__.py created." should happen after the creation has happened.
7. Use mkdir -p to allow for nested directories to also be created (if needed).
8. Let script throw error and stop as early as possible on errors. This is achieved with set -e.

---

Together:

#!/bin/sh
set -e
dir_name="1ドル"
file_name="2ドル"
test_dir="test/${dir_name}"
file_in_dir="${test_dir}/${file_name}.py"
add_file() {
 if test -f "${file_in_dir}"
 then
 echo "File already exists in directory, exiting."
 exit 0
 else
 touch "${file_in_dir}"
 fi
}
create_dir() {
 mkdir -p "${test_dir}"
 touch "${test_dir}/__init__.py"
 echo "Directory and __init__.py created."
}
[ ! -d "${test_dir}" ] && create_dir "${test_dir}"
add_file

The chunk of variable declarations (dir_name, file_name etc.) could also be localised to functions.

• Toby Speight: You missed "extract common lines from if/else" from the list - though you've demonstrated in your reworked code.
• Edwin Carlsson: Thank you for your brilliant advice. One question: what is the difference between the double brackets and single brackets in my contra your implementation? Does it have to do with POSIX compliance?
• chicks: stackoverflow.com/q/669452/2002471 explains why double brackets are a good thing. Striving for POSIX-compliance after bash and Linux has taken over the world is an interesting prioritization. I'd hope that code readability and maintainability are more important these days. Going from if [[ to if test makes sense to people who understand how shell if's work, but I'd say it makes it less readable and intuitive for most folks.