check_file_existence.sh

until  [ -e /tmp/file1 ] 
# It checks for the existence of a file; 
#-d se vuoi vedere se una directory esiste
#attento che se il link e' simbolico, allora devi chiedere -L, oppure se non funziona propria usa -d e il path completo
do
    echo "Io esisto"
done

if  [ ! -e /tmp/file1 ] # It checks for the existence of a file
then
    echo "file1 non esiste"
fi
FILE TEXT OPERATORS IN BASH

check if file not empty:
    
    if [-s file]

       -b FILE
              FILE exists and is block special
       -c FILE
              FILE exists and is character special
       -d FILE
              FILE exists and is a directory
       -e FILE
              FILE exists
       -f FILE
              FILE exists and is a regular file
       -g FILE
              FILE exists and is set-group-ID
       -G FILE
              FILE exists and is owned by the effective group ID
       -h FILE
              FILE exists and is a symbolic link (same as -L)
       -k FILE
              FILE exists and has its sticky bit set
       -L FILE
              FILE exists and is a symbolic link (same as -h)
       -O FILE
              FILE exists and is owned by the effective user ID
       -p FILE
              FILE exists and is a named pipe
       -r FILE
              FILE exists and read permission is granted
       -s FILE
              FILE exists and has a size greater than zero
       -S FILE
              FILE exists and is a socket
       -t FD  file descriptor FD is opened on a terminal
       -u FILE
              FILE exists and its set-user-ID bit is set
       -w FILE
              FILE exists and write permission is granted
       -x FILE
              FILE exists and execute (or search) permission is granted