Check if filename exist from inline command

Question

I have a file named input.txt with this contents:

...
FILE "Edie - Realities.txt" TXT
...

And I want to read it, then strip filename path from line that starts with FILE, and check if it exists, so:

[ -f $(cat input.txt | grep FILE | grep -o "\".*\"") ] && echo "exist" || echo "does not exist"

but this outputs:

[: too many arguments  
does not exist

If I run:

echo $(cat input.txt | grep FILE | grep -o "\".*\"")

I get what I expected:

"Edie - Realities.txt"

So why is this, or how can I solve this problem?

Answer 1

$(...) is evidently passing "Edie, -, and Realities.txt" as separate arguments. You need to quote $(...) like any other $variable, and you probably want to remove the "s.

[ -f "$(cat input.txt | grep FILE | sed 's/^.*"\(.*\)".*$/\1/')" ] && echo "exist" || echo "does not exist"

Answer 2

You need to quote the argument to -f -- if you run with set -x you'd see the command being performed is [ -f '"Edie' '-' 'Realities.txt"' ] which is too many arguments.

[ -f "$(sed -e '/FILE/!d' -e 's/FILE "\([^"]*\).*/\1/' input.txt)" ]

If you have GNU grep on your system, you can use:

[ -f "$(grep -Po '(?<=FILE ").*(?=")' input.txt)" ] 

Answer 3

For your file contents

FILE "/path_to_file/filename" TXT

do something like

grep FILE  input.txt | while read line 
  do
    fname=`echo $line | awk -F\" '{print $2}'`  # this separates the line by the quotes
                                                # result is like /path_to_file
    echo $fname # just to check it 
    if [ -f $fname ]
    then
      ls -l $fname
      echo "file exists"
    else
      echo "no file there $file"
    fi
  done