2

I don't understand why the last part of my script does not display anything when no file or directory is found.

echo -n "Please enter a filename or directory: "
read filename
if [ -z "$filename" ]; then
  echo "You did not enter anything!"
  exit 1
fi
if [ -e "$filename" ]; then
  if [ -f "$filename" ]; then
    echo "You entered a file."
  elif [ -d "$filename" ]; then
    echo "You entered a directory."
  else
    echo "You did not enter a valid file or directory."
  fi
fi
exit

I don't know what's wrong with my code. It will not display the echo if an invalid or nonexistent file or directory is inputted.

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2 Answers 2

Reset to default
4

I re-formatted your script to indent the if statements. Doing so made it clearer that your last echo only happens if -f is true and -d is false. If the user enters a file or directory that doesn't exist, then -f fails.

Consider this revision to your last section:

if [ -e "$filename" ]; then
  if [ -f "$filename" ]; then
    echo "You entered a file."
  elif [ -d "$filename" ]; then
    echo "You entered a directory."
  fi
else
  echo "You did not enter a valid file or directory."
fi

Where the true section of the first if statement is ended earlier (by else); then files/directories that don't exist have a section of code to execute.

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7
  • Still trying to comprehend this. So my order is wrong? Commented Nov 2, 2015 at 0:51
  • I wouldn't say the order was wrong so much as the logic. See my recent edit for code & explanation. Commented Nov 2, 2015 at 0:56
  • I see. Just one of those things I overlooked, but makes a big difference. Good eye Jeff thanks. Commented Nov 2, 2015 at 0:59
  • 1
    It's easy to get lost in deeply-nested statements, which is why the first thing I wanted to do was edit your code to indent it. Another thing I'll do when writing code where I know nested statement are coming is to write the "structure" (if/elif/else/fi) in direct sequence, so that I know which section deals with what, then go fill in the blanks. Commented Nov 2, 2015 at 1:02
  • 1
    btw, see stackoverflow.com/questions/28832899/… Commented Nov 2, 2015 at 1:09
3

There are many other types of files that will not cause any output in this code. These include symbolic links, named pipes, sockets, and block and character special files. Notably, /dev/tty, /dev/stdin, /dev/stdout and /dev/stderr fall through, undetected by the code.

You could modify the logic to account for this, however, this structure (case statement style structure) is easier to read and less error-prone: 

if [ ! -e "$filename" ]; then
    echo "$filename does not exist"
    exit 1
elif [ -f "$filename" ]; then
    echo "You entered a file."
elif [ -d "$filename" ]; then
    echo "You entered a directory."
else 
    echo "$filename is not a regular file or directory."
    exit 2
fi
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