CODEWITHSUNDEEP
shellvariablesinput
user3334019
user3334019

Reputation: 25

Until user input equals something do - Follow up

Following up on someone else's question titled "Until user input equals something do". My script asks user for a filename. The script must search for the file. If the file does not exist in the directory, user must again be prompted for filename until they enter file that exists (must persist until true, without exiting program). Would it look something like?: 

printf "Enter filename: "
read ifile
while [[ ! -e "$ifile" ]]
do
  printf "File $ifile not found! "
done

When a file that does not exist is entered, I get a "runaway" loop until I have to cancel (CNTL + C). Example: If file filesa exists, but user "fat-fingers" it as filessa

Enter filename: filessa File filessa not found! File filessa not found! File filessa not found! File filessa not found! File filessa not found! File filessa not found! ...........on and on and on.

Any help is greatly appreciated!

Upvotes: 0

Views: 138

Answers (2)

chepner
chepner

Reputation: 531315

There is an until loop in bash:

until [[ -e $ifile ]]; do
    [[ -z $ifile ]] || printf "File $ifile not found!\n"
    read -p "Enter filename: " ifile
done

Actually, until is part of the POSIX standard as well, although a POSIX-compliant example would be less concise:

until [ -e "$ifile" ]; do
    [ -z "$ifile" ] || printf "File $ifile not found!\n"
    printf "Enter filename: "
    read ifile
done

Upvotes: 1

shellter
shellter

Reputation: 37288

Try this

printf "Enter filename: "
read ifile
while [[ ! -e "$ifile" ]]
do
  printf "File $ifile not found! \n"
  printf "Enter filename: "
  read ifile
done

If the user has entered the wrong filename, then you have to ask them to try again ;-).

Also, if the user doesn't enter anything, that will produce a different error. I would write the more extended check as

printf "Enter filename: "
read ifile
while [[ ! -e "${ifile:-XXXXno_user_inputXXXX}" ]]
do
  printf "File ${ifile:-XXXXno_user_inputXXXX} not found! \n"
  printf "Enter filename: "
  read ifile
done

The var syntax ${var:-defaultValue} can be read as "if the variable $var is empty, then print the value after the :- as a replacement value.

A pedantic objection to XXXXno_user_inputXXXX is that it's possible that there might be a file in your directory already named XXXX_no_user_inputXXXX, so you'll have to decide if that is a big risk for your project.

IHTH

Upvotes: 1

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