How to check if a file is created/deleted/changed (Bash)

Question

declare -i fil="$1"
declare -t tid="$2"
notFinished=true
finnes=false

if [ -f $fil ];
then
finnes = true
fi

while $notFinished;
do

if [ -f $fil && ! $finnes ];          (14)
then
echo "Filen: $fil ble opprettet."
finished=true
fi

if [ ! -f $fil && $finnes ];         (20)
then
echo "Filen: $fil ble slettet."
finished=true
fi

sleep $tid
done

I'm trying to check if a file with the name $fil gets created, or deleted during the life of the script, only checking every $tid seconds. I also want to check if the file gets changed by comparing timestamps, but i'm not really sure how to do this.. Just want to mention that this is the first time trying to program in this language.

The only error i'm getting right now is:

  /home/user/bin/filkontroll.sh: line 14: [: missing `] '
  /home/user/bin/filkontroll.sh: line 20: [: missing `] '

@edit: fixed notFinished and some spacing

Answer 1

You can use something like this:

#!/bin/bash

declare -i fil="$1"
declare -t tid="$2"
notFinished=true
finnes=false

if [ -f "$fil" ]; then
   finnes=true
fi

while [ "$notFinished" = true ];
do
    if [ -f "$fil" ] && [ ! "$finnes" = true ]; then
       echo "Filen: $fil ble opprettet."
       finished=true
    fi

    if [ ! -f "$fil" ] && [ "$finnes" = true ]; then
       echo "Filen: $fil ble slettet."
       finished=true
    fi

    sleep $tid
done

Note you should read How to declare and use boolean variables in shell script? interesting question and answer (link to the answer I prefer), so that you can see the boolean checkings should be done like this (this applies to the if but also to the while):

if [ "$bool" = true ]; then

Also, note I quoted variables. It is a good practice that will avoid you getting crazy sometimes with strange behaviours when the variables are not set.

Answer 2

me@box:/tmp $ if [ a ] ; then echo foo; fi
foo
me@box:/tmp $ if [ b ] ; then echo foo; fi
foo
me@box:/tmp $ if [ a && b ] ; then echo foo; fi
bash: [: missing `]'
me@box:/tmp $ if [ a ] && [ b ] ; then echo foo; fi
foo
me@box:/tmp $ if [[ a && b ]] ; then echo foo; fi
foo