我正在编写一个 shell 脚本，需要在“if then”语句中组合“find”和“grep”

Question

I have been working on a Script that automatically changes my Macbooks wallpaper based on the currently connected SSID. and it will select a new wallpaper every 30min

Long story short it's working fine, but im trying to create the illusion of "randomness" by not allowing the script to repeat the same wallpapers too often.

The command to pull a wallaper currently looks like this;

find -E -L ~/WallAware/A -type f -regex ".*\.(jpg|gif|png|jpeg)" \( -atime +5 -o -mtime -1 \) | ~/WallAware/gshuf -n 1

Which I mistakenly thought would work.

So what I need to do is:

1. use find to get a random file from a folder with an access time of 5+ days (This will prevent wallpapers being repeated too often)
2. If there is no file with an access time of 5+ days, then get a file with a modified time of -1 (This will prioritize new wallpapers if all other have been seen in the last 5 days)
3. If it cant do either of those then just pick a random file.
4. put the path to the selected wallpaper in the variable "$B"

I am very much still learning, I am documenting my progress over at Github for fun.

Answer 1

I would do the following:

#!/bin/sh

my_find() {
    find -type f '(' -false $(for ext in png jpg gif jpeg; do echo "-o -name *.$ext"; done) ')' "$@"
}

if my_find -atime +5 -print -quit | grep .; then
    B=$(my_find -atime +5 | shuf -n 1)
elif my_find -mtime -1 -print -quit | grep .; then
    B=$(my_find -mtime -1 | shuf -n 1)
else
    B=$(my_find | shuf -n 1)
fi

# then do your stuff with B

Feel free to replace shuf by gshuf if you are on Mac OS X. I am not sure find on Mac OS X will have all these options though. -quit is optional. Also you could put extensions in a variable ( $exts ).

Edit: from this SuperUser post :

The difference? Spotlight doesn't index /tmp, but it does index ~. I'm pretty sure that what you're seeing here is spotlight reading the file to index it after you change the atime - which then sets the atime back to now.

I believe this could be your atime issue. Otherwise atime should work just fine on Darwin. You could either add your path to exceptions, or use a path not indexed by Spotlight ( /wallpapers could work).