How can I check if user input is in correct format?
My script:
#!/bin/bash
echo 'Enter 3 numbers separated by comma'
read text
#here i want to check if user input is in correct format
I want user input look like this: 1,2,3.
But when user input will look e.g like this: 123 or: 1.2.3 an error text message will pop up.
Maybe I have to use arguments but I don't know how?
see man bash, you can test a variable with regular expressions:
[[ $text =~ ^[0-9]+,[0-9]+,[0-9]+$ ]] || echo wrong format
Example:
$ text=1,a,4
$ [[ $text =~ ^[0-9]+,[0-9]+,[0-9]+$ ]] || echo wrong format
wrong format
$ text=1,12,34
$ [[ $text =~ ^[0-9]+,[0-9]+,[0-9]+$ ]] || echo wrong format
$
You can compare the input string to a pattern.
#!/bin/bash
while true; do
read -p 'Enter 3 numbers separated by comma' -r text
case $text in
*[!,0-9]* | *,*,*,* | ,*,* | *,*, ) ;;
*,*,* ) break;;
esac
echo invalid
done
Your processing will be much easier if you require whitespace instead of commas between the values, though.
#!/bin/bash
while true; do
read -p 'Enter 3 numbers separated by space' -r first second third
case $first,$second,$third in
*[!,0-9]* | *,*,*,* | ,*,* | *,*, ) ;;
*,*,* ) break;;
esac
echo invalid
done
In brief, each expression between | up to ) is examined like a glob pattern (what you use for file name wildcards, like *.png or ?.txt); the subpattern [!abc] matches a single character which is not a, b, or c; these consecutive characters can also be expressed as a range [!a-c].
So, we reject anything which contains a character which isn't a number or a comma, anything with too many commas, anything with commas at the edges, and (implicitly, by falling through) anything with too few commas.
if [$text =~ *,*,*] then echo 'correct' else echo 'not correct' fi[ ... ] syntax requires spaces inside the brackets.