如何使用 Xidel 从图像 @srcset 属性中获得图像的最佳分辨率？

Question

我有这段代码可以从@srcset 属性中列出图像的大小：

cat <<EOF | xidel -s - -e 'extract(//@srcset,"(\d+w)",1,"*")'
<img ... srcset="https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w, 
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w" />
EOF

696w
220w
300w
768w
475w
800w
741w
640w

如何使用 Xidel 获得最佳分辨率？在这种情况下，只有800w? 最大的尺寸可以在开头、结尾或中间（随机顺序）。

Xidel 预期输出：

cat <<EOF | xidel -s - -e '?'
<img ... srcset="https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w, 
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w" />
EOF

800w

或输出完整的网址：

cat <<EOF | xidel -s - -e '?'
<img ... srcset="https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w, 
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w" />
EOF

https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg

Answer 1

要提取最大宽度，只需在其周围加上max()：-e 'max(extract(//@srcset,"(\d+w)",1,"*"))'。

要提取宽度最大的网址，您首先必须拆分每个网址：

$ cat <<EOF | xidel -s - -e 'tokenize(//@srcset,", ")'
<img srcset="https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w" />
EOF

https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w
https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w

然后，令我惊讶的是，您可以再次将 max() 包裹起来：

$ cat <<EOF | xidel -s - -e 'max(tokenize(//@srcset,", "))'
<img srcset="https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-696x457.jpg 696w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-220x144.jpg 220w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-300x197.jpg 300w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-768x504.jpg 768w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-475x312.jpg 475w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-741x486.jpg 741w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu-640x420.jpg 640w, https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w" />
EOF

https://www.jewishpress.com/wp-content/uploads/Billionaire-Arnon-Milchan-and-PM-Benjamin-Netanyahu.jpg 800w

仅返回您可以执行的网址：-e 'substring-before(max(tokenize(//@srcset,", "))," ")'。