File download automation in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this wget command?

You run this command in a terminal:

wget -q --show-progress https://example.com/file.txt -O downloaded.txt && echo "Done"

What will be printed on the terminal?

Bash Scripting

wget -q --show-progress https://example.com/file.txt -O downloaded.txt && echo "Done"

A No output at all

B Progress bar showing download progress

C Done

D Error message about missing file

💡 Hint

The -q option means quiet, but --show-progress overrides some quietness.

https://example.com/file.txt returns 404 Not Found, so wget exits non-zero and "Done" is not printed. -q suppresses error messages, and --show-progress does not show progress if the download fails immediately.

📝 Syntax

intermediate

Which script correctly downloads multiple files in a loop?

You want to download files from URLs stored in a file named urls.txt, one URL per line. Which script snippet correctly downloads each file using curl?

A for url in $(cat urls.txt); do curl -O "$url"; done

B while read url; do curl -O "$url"; done < urls.txt

C cat urls.txt | for url in $urls.txt; do curl -O "$url"; done

D for url in urls.txt; do curl -O "$url"; done

💡 Hint

Think about how to read lines safely from a file in bash.

Option B uses a while read loop to read each line safely from the file. Option B splits on spaces which can break URLs with spaces. Option B is invalid syntax. Option B treats the filename as a URL.

🔧 Debug

advanced

Why does this script fail to download files correctly?

Consider this script:

urls=("http://site.com/file 1.txt" "http://site.com/file2.txt")
for url in "${urls[@]}"; do
  curl -O "$url"
done

It fails to download the first file. What is the problem?

Bash Scripting

urls=("http://site.com/file 1.txt" "http://site.com/file2.txt")
for url in "${urls[@]}"; do
  curl -O "$url"
done

A The space in the URL is not encoded, causing curl to fail.

B The array syntax is wrong; it should use single quotes.

C The for loop syntax is invalid; it needs a semicolon after do.

D curl cannot handle URLs with numbers.

💡 Hint

Spaces in URLs must be encoded as %20.

curl fails because the URL contains a space character which is invalid in URLs. It should be encoded as %20 to work properly.

🚀 Application

advanced

How to automate retrying downloads on failure?

You want a bash script that tries to download a file with curl up to 3 times if it fails. Which snippet achieves this?

A curl -O http://example.com/file.txt; if [ $? -ne 0 ]; then curl -O http://example.com/file.txt; fi

B curl -O http://example.com/file.txt || curl -O http://example.com/file.txt || curl -O http://example.com/file.txt

C for i in {1..3}; do curl -O http://example.com/file.txt && break; done

D while curl -O http://example.com/file.txt; do break; done

💡 Hint

Use a loop with a break on success.

Option C tries up to 3 times and stops if curl succeeds. Option C tries sequentially but is less clear. Option C loops only if curl succeeds, so it breaks immediately. Option C tries only twice and no loop.

🧠 Conceptual

expert

What is the best way to download files securely in a script?

You want to automate file downloads in bash but ensure the files are not tampered with. Which approach is best?

A Download files and trust the source without verification.

B Use wget with --no-check-certificate to avoid SSL errors.

C Download files only over HTTP to avoid SSL overhead.

D Download files with curl and then verify their SHA256 checksum against a trusted value.

💡 Hint

Think about verifying file integrity after download.

Verifying the checksum ensures the file is exactly what you expect and not tampered with. Ignoring SSL or using HTTP is insecure.