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Comments on How to write a bash function to sanitize filenames for Linux and Windows


How to write a bash function to sanitize filenames for Linux and Windows


I'm trying to write a bash function that can sanitize filenames to make them compatible with both Linux and Windows file systems. The function should perform the following operations:

  1. Replace invalid characters with similar valid ones (e.g., replace * or + with - or _, ? with ¿, etc).
  2. Remove leading and trailing spaces before the file extension.
  3. Replace multiple consecutive spaces, carriage returns, etc., with a single space.
  4. Replace single spaces with underscores (_).

Here's the function I've come up with:

sanitize_filename() {
    local input_str="$1"
    # Replace invalid characters
    input_str="${input_str//[^a-zA-Z0-9_\-\. ]/-}"
    # Remove spaces at the beginning and end before the extension
    # Replace multiple spaces, carriage returns, etc. with a single space
    input_str=$(echo "$input_str" | tr -s '[:space:]' | tr -s '\r')
    # Replace single spaces with underscore
    input_str="${input_str// /_}"
    echo "$input_str"

# Test cases
    "my file 123.txt"
    "   leading_spaces.docx"
    "trailing_spaces   .txt"
    "multiple    spaces.txt"
    "multiple  +  spaces.txt"
    "carriage\r\r return.txt"

# Expected sanitized filenames

# Test the function
for ((i=0; i<${#test_cases[@]}; i++)); do
    result=$(sanitize_filename "${test_cases[i]}")
    if [ "$result" == "${expected[i]}" ]; then
        echo "Test $i: PASSED"
        echo "Test $i: FAILED"
        echo "Expected: ${expected[i]}"
        echo "Got: $result"

I get the following output:

❯ ./
Test 0: PASSED
Test 1: FAILED
Expected: my-file-123¿.txt
Got: my-file-123-.txt
Test 2: FAILED
Expected: file_with_special-characters.jpg
Got: file_with-special-characters.jpg
Test 3: PASSED
Test 4: FAILED
Expected: trailing_spaces.txt
Got: trailing_spaces_.txt
Test 5: PASSED
Test 6: FAILED
Expected: multiple-spaces.txt
Got: multiple_-_spaces.txt
Test 7: FAILED
Expected: carriage_return.txt
Got: carriage-r-r_return.txt

How can I fix this function to handle all the test cases correctly?

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2 comment threads

Broken by design? (1 comment)
Vague and unfocused (1 comment)
Vague and unfocused
Karl Knechtel‭ wrote 2 months ago

There seem to be many separate questions here. Please start by trying to make functions to implement the individual rules that you have in mind, and testing them. Then, the requirements for those rules need to be clearer for anyone to be able to help with them. For example, how should we know which characters are "invalid" (according to whom? What concrete problem do you hope to solve by this replacement?), and what is "similar" to each for the replacement? And what part of the existing code are you expecting to implement that logic? I don't see ¿ anywhere in the code, so it's hard to imagine how it could be expected to replace ? with ¿.