Shell脚本：检查列表文件中目录中是否存在文件

Question

I am trying to check if file names listed in a text file exist in a directory. If the file name in medialist.txt exists in the medialab directory put the file name in foundfiles.txt otherwise put the file name in lostfiles.txt. Where I am having difficulty is passing a single file name from medialist.txt into the if statement. How would I pass a single file name from medialist.txt to the if statement?

The following block of code is what I have come up with so far.

for i in $(cat /home/user/Downloads/medialab/medialist.txt)
do
   if [[ $([[ -e $i ]]) == $(ls /home/user/Downloads/medialab/)  ]]
   then
           echo "$i" > /home/user/foundfiles.txt
   else
           echo "$i" > /home/user/lostfiles.txt
   fi
done

I have experimented with the xargs command in the if statement. This would replace the current if statement in the for loop above. I would remove the LS variable, it is just for testing the if statement on its own. Here is the example:

LS=$(ls /home/user/Downloads/medialab/)

if [[ -e $(xargs echo "$LS") ]]
then    
    echo "$i" > /home/user/foundfiles.txt
else    
    echo "$i" > /home/user/lostfiles.txt
fi

Answer 1

You can just read the file in a while-loop and check if the path is a file with the -f (checks if the given path is a file) switch, like so:

while read -r || [[ -n $REPLY ]]; do
    [[ -z $REPLY ]] && continue
    if [[ -f "/home/user/Downloads/medialab/${REPLY}" ]]; then
        echo "$REPLY" >> "/home/user/foundfiles.txt"
    else
        echo "$REPLY" >> "/home/user/lostfiles.txt"
    fi
done < "/home/user/Downloads/medialab/medialist.txt"

What's happening here is we're reading the inputfile with a redirection to the while loop, using read to read the input into a variable using the inbuilt $REPLY variable, then the || [[ -n $REPLY ]] || [[ -n $REPLY ]] handles an inputfile that doesn't end with a newline.

Next we check if the variable is empty with -z , this handles empty lines in the middle of the file skipping them with continue .

Then we check if the string in the now populated $REPLY variable is a file with -f (expanding the filename as a part of the path in quotes) and append the appropriate file with >> .

Note how using [[ as the test, you don't need to quote the LHS variable, but you do need to quote a RHS variable (as well as variables in pretty much any other use).