Login or Register to Ask a Question and Join Our Community


Shell Programming and Scripting

Would like to check user input for letters within a loop

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Would like to check user input for letters within a loop
# 8  
Old 12-14-2018
You can shorten it like this:
Code:
while
  printf "Please input a number: "
  read number
  [[ -z "$number" ]] || [[ $number == *[^0-9]* ]]
do
  echo "That is not a number"
done
echo "That is a number, Good Job!"

You can even stagger the conditions, via two nested while loops:
Code:
while
  while
    printf "Please input a number: "
    read number
    [[ -z "$number" ]]
  do
    :
  done
  [[ $number == *[^0-9]* ]]
do
  echo "That is not a number"
done
echo "That is a number, Good Job!"

How does it work?
The definition for a while loop is
Code:
while list
do list
done

where list is any (even multi-line, but not empty) shell code.
The last exit code in the while list determines if the loop should run or terminate.
The : is a no-op command that prevents an empty do list.
Last edited by MadeInGermany; 12-14-2018 at 03:57 PM..
This User Gave Thanks to MadeInGermany For This Post:
jvezinat
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

How to check the user input to be valid using shell script?

How to check the user input to be valid using shell script? The valid input is in the format like as follows. 1. It can only have r,w,x or a hyphen and nothing else. 2. ensure the r, w, x are in the correct order. for example: rwxr-xr-x is a valid format. Thanks (5 Replies)
Discussion started by: hyeewang
5 Replies

2. Shell Programming and Scripting

How-To Check & Filter user input

Hi, On my Java webpage which invokes the shell script has two checkboxes viz ... apache and weblogic apache require one parameter i.e apache home from the user while Weblogic requires three or five params from the user vi.z weblogic_home or <jdk_home, config_home & pid>, username and... (4 Replies)
Discussion started by: mohtashims
4 Replies

3. Shell Programming and Scripting

Loop breaks on yes/no user input

I have a shell script, and its pretty much done, I decided to add a loop that ends or continues depending on user input. like "would you like to continue?" and if I hit y or yes it will run the loop again until I hit n or no and breaks out of the loop. To be hones I didn't think I needed to add... (2 Replies)
Discussion started by: Demon_Jester
2 Replies

4. Shell Programming and Scripting

Check user input

Hi, I need my script to check if the user enters 3 values if not 5 values to my script and alert if the input has any other number of values. for example: ./myscript.sh 22 56 3221 - > correct ./myscript.sh 22 56 3221 45 777 -> correct ./myscript.sh 22 56 3221 45 -> incorrect Please... (6 Replies)
Discussion started by: mohtashims
6 Replies

5. Homework & Coursework Questions

Function to Check if string input from user is alphabetic only

Good Evening. I'm new to C. Can you please help me. I'm creating an error checking function, user will input a string, this will check if the input is all alphabet or all letters only. If there is a digit or other special char, it will print Error then ask input from user again. Here's my... (1 Reply)
Discussion started by: eracav
1 Replies

6. Shell Programming and Scripting

matching user input to a text file loop?

until do read -p "Invalid cars. Try againa" cars1 done Ok i have the above code, im getting users input and if it doesnt match in the file the user has to try again untill its correct But when i run this it gives me an error saying ./Cars.bash: line 43: (2 Replies)
Discussion started by: gangsta
2 Replies

7. UNIX for Dummies Questions & Answers

Getting user input from inside a while loop?

I'm new to BASH and i'm trying to create a script which is simply put a large find and replace file. This is what I have so far N=0 while read LINE ; do N=$((N+1)) sed 's/'$2'/'$3'/g' $LINE > .temp echo "Changes to file $N = $LINE" echo 'The following changes... (5 Replies)
Discussion started by: Azumandious
5 Replies

8. UNIX for Dummies Questions & Answers

how to check the user input from terminal

Hello everybody!!! I am writing my own rm command in unix. I prompt the user to type if he wants to delete a file and then read what he typed. But how do i check what he typed? This is my program so far: echo 'Delete prog1.c (y/n)?' read yesOrNo if yesOrNo == 'y' then rm prog1.c... (6 Replies)
Discussion started by: mskart
6 Replies

9. Shell Programming and Scripting

Loop until user input is correct

Hello, i know how to retrieve a user input (read), and how to manage the different options (case statement). But... could anybody show me a script that, if the user option is incorrect, don't allow to continue the excution, i.e., if the value entered is not 1 or 2, the script shows a question. ... (2 Replies)
Discussion started by: aristegui
2 Replies

10. UNIX for Dummies Questions & Answers

read user input from within a wile loop that is being fed from below

hi! i need to do a ksh script that uses a wile loop that is fed form below while read line do some things done < myfile inside the while loop i need to read user input to ask the user what he wants to do, but "read" reads the file, and not the standard input while read line do ... (2 Replies)
Discussion started by: broli
2 Replies
Login or Register to Ask a Question