# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/<img src=".*?((\/img\/[^"]+)\/thumbs\/([^"]+))".*alt="(.*?)"[^>]*class="([^"]*popup-img[^"]*)"[^>]*>/<a class="$5" href="..$2\/$3" title="$4" style="background: url('..$1');-webkit-background-size: cover;background-size: cover;"><\/a>/gmi;t' <<< "<img src=\"http://example/img/product/name/thumbs/100/img1.jpg\" alt=\"описание фото1\" width=\"100\" height=\"100\" caption=\"false\" class=\"popup-img\" />
<img src=\"http://example/img/product/name/thumbs/100/img2.jpg\" alt=\"описание фото2\" width=\"100\" height=\"100\" caption=\"false\" class=\"popup-img left\" />
<img src=\"http://example/img/product/name/thumbs/100/img2.jpg\" alt=\"описание фото2\" width=\"100\" height=\"100\" caption=\"false\" class=\"wrong-class left\" />"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html