How to tell curl to check file existence before download?

Question

I use this command to download a series of images:

curl -O --max-time 10 --retry 3 --retry-delay 1 http://site.com/image[0-100].jpg

Some images are corrupted, so I delete them.

for i in *.jpg; do jpeginfo -c $i || rm $i; done

How to tell curl to check file existence before download?

I can use this command to prevent curl override existing images:

chmod 000 *.jpg

But I don't want to re-download them.

Answer 1

If the target resource is static, curl has an option -z to only download a newer target copy.

Usage example:

curl -z image0.jpg http://site.com/image0.jpg

An example for your case:

for i in $(seq 0 100); do curl -z image$i.jpg -O --max-time 10 --retry 3 --retry-delay 1 http://site.com/image$i.jpg; done

Answer 2

No idea about doing it with curl, but you could check it with Bash before you run the curl command.

for FILE in FILE1 FILE2 …
do
  if [[ ! -e $FILE ]]; then
    # Curl command to download the image.
  fi
done