如何在路径字符串中使用if_existing语句？

Question

Im trying to chech if the file exists in conky using ${if_existing ..} as follows:

    ${if_existing /home/stanislav/.cache/yandexweather/bkn_n.png}YES \
    ${else}NO
    ${endif}\

And this works perfectly. However how can I use ${if_existing ..} statement with an output of another command? For Example:

    ${if_existing echo "~/.cache/yandexweather/"$(python ~/.cache/yandexweather/yw_script.py -image_0)}YES \
    ${else}NO
    ${endif}\

The latter doesnt work

Answer 1

You could use ${eval ...} to have the shell command calculated first, then having the ${if_...} part parsed. For example,

${eval $${if_existing ${execi 10 echo "myfile"}}\
          YES $${else} NO $${endif} }

Inside the eval, the if.. else and endif parts are made to not work by doubling the $ to $$ . However, the ${execi part runs and executes the shell command ( echo ... ) every 10 seconds (choose a big value if your expression will never change).

After the execi has returned the string ( myfile , in this example), the resulting command is parsed again. Each $$ has been evaluated to $ , so we have:

${if_existing myfile} YES ${else} NO ${endif}