[SOLVED] conditional statements: Forgot how to read both capital/ lower case

andrew.comly · 06-21-2016, 06:31 AM

Before I am sure that I saw some tutorial that taught that you can write a program with a if/else conditional statements that can accept the following answers:

Quote:

1) Yes
2) YEs
3) YES
4) yes
5) yES
6) yeS
7) YeS
8) yEs

My failed attempt below:

Code:

#!/bin/bash

unset ans

echo -en "Enter into call mode? > "  
read ans

#Conditional statement
	if [ "$ans" == "[Yy][Ee][Ss] ]; then
		echo "You answered "$ans", Welcome!"
	
	elif [ "$ans" == "[Nn][Oo]" ]; then
		echo "You answered "$ans", Denied"
	else
		echo "Input not valid."
	fi

There must be something wrong with my web searching skills or something not to be able to find this again. The answer stems off of [0-9a-zA-Z] being shorthand for numbers 0-9, lower case letters a-z and upper case letters A-Z. I even searched in the ebooks: Bash Beginners Guide and Advanced Bash Scripting.

pan64 · 06-21-2016, 06:59 AM

see man bash,

Code:

[[ "$ans" =~ [Yy][Ee][Ss] ]]
1. must use [[ and ]] instead of [ ]
2. must not use " " around the regexp
3. =~ is the comparator, not ==

michaelk · 06-21-2016, 07:07 AM

Too late... What you are searching for is conditionals using regular expressions.

[[ <string> =~ <regex> ]]

sundialsvcs · 06-21-2016, 07:53 AM

Generally speaking, languages are case-sensitive in string comparison. (But, as always, there are exceptions.) Regular expressions (with the "/i" modifier) can reliably be used to do case-insensitive compares. Or, you can use a "to-upper/lower case" function and compare against a literal of that case.

grail · 06-21-2016, 08:12 AM

I use bashes butilin ^^ or ,, to shift entire string to upper or lower case and then do basic string test:

Code:

[[ ${ans^^} == "YES" ]]

gnashley · 06-21-2016, 11:38 AM

[ "$ans" == "[Yy][Ee][Ss] ]
also missing closing double quote

keefaz · 06-21-2016, 12:11 PM

Another way is to use shopt -s nocasematch

Code:

shopt -s nocasematch
if [[ $ans == "yes" ]]; then
    echo "You answered '$ans', Welcome!"
	
  elif [[ $ans == "no" ]]; then
    echo "You answered '$ans', Denied"
  else
    echo "Input not valid."
  fi

Habitual · 06-21-2016, 12:13 PM

Quote:

Originally Posted by keefaz

Another way is to use shopt -s nocasematch

Code:

shopt -s nocasematch
if [[ $ans == "yes" ]]; then
    echo "You answered '$ans', Welcome!"
	
  elif [[ $ans == "no" ]]; then
    echo "You answered '$ans', Denied"
  else
    echo "Input not valid."
  fi

Good Stuff, Maynard!
Thanks!

andrew.comly · 06-21-2016, 10:41 PM

It WAS in Advanced Bash Scripting's Chapter 18.1. "A Brief Introduction to Regular Expressions" online eBook under the "Brackets -- [...] -- enclose a set of characters to match in a single RE." section in the sentence beginning with "Combined sequences".

I originally looked in the wrong chapter!! More specifically:
Chapter 9. Another Look at Variables...
Chapter 10. Manipulating Variables.

andrew.comly · 06-22-2016, 12:00 AM

Special thanks to pan64, grail and keefaz for your solutions!!

Synopsis:

Quote:

Originally Posted by pan64

Code:

[[ "$ans" =~ [Yy][Ee][Ss] ]]
1. must use [[ and ]] instead of [ ]
2. must not use " " around the regexp
3. =~ is the comparator, not ==

Quote:

Originally Posted by grail

Code:

[[ ${ans^^} == "YES" ]]

Quote:

Originally Posted by keefaz

Code:

shopt -s nocasematch
if [[ $ans == "yes" ]]; then
    echo "You answered '$ans', Welcome!"
	
  elif [[ $ans == "no" ]]; then
    echo "You answered '$ans', Denied"
  else
    echo "Input not valid."
  fi