Shell file size in Linux

filesize=$(stat -c '%s' testing.txt)

You can do it this way with ls (check the man page for the meaning of -s)

var=$(ls -s1 testing.txt | awk '{print $1}')

Or you can use stat with -c '%s'.

Or you can use find (GNU):

var=$(find testing.txt -printf "%s")

size() {
  file="$1"
  if [ -b "$file" ]; then
    /sbin/blockdev --getsize64 "$file"
  else
    wc -c < "$file"  # Handles pseudo files like /proc/cpuinfo
    # stat --format %s "$file"
    # find "$file" -printf '%s\n'
    # du -b "$file" | cut -f1
  fi
}

fs=$(size testing.txt)

size=`ls -l | grep testing.txt | cut -f6 -d' '`