CPP

convert uppercase to lowercase

// C++ program to convert whole string to
// uppercase or lowercase using STL.
#include<bits/stdc++.h>
using namespace std;
  
int main()
{
    // su is the string which is converted to uppercase
    string su = "Jatin Goyal";
  
    // using transform() function and ::toupper in STL
    transform(su.begin(), su.end(), su.begin(), ::toupper);
    cout << su << endl;
  
    // sl is the string which is converted to lowercase
    string sl = "Jatin Goyal";
  
    // using transform() function and ::tolower in STL
    transform(sl.begin(), sl.end(), sl.begin(), ::tolower);
    cout << sl << endl;
  
    return 0;
}

onvert it to lower case letter if it’s an upper case letter and convert it to upper case letter if it’s a lower

#include<iostream>
#include<string>
using namespace std; 

int main() 
{ 
    string str="Hello World"; 
    int i;
    
    cout<<"The String is: 
"<<str;
    cout<<endl<<endl;
    
    cout<<"String after uppercase lowercase modification: 
";
    for(i=0; i < str.length(); i++)
    {
        //if its uppercase add to its Ascii code 32 to make lowercase
        if(str[i]>='A' && str[i]<='Z')
      	cout<<char(str[i]+32);
      	
      	// else if its lowercase subtract 32 to make it upper case 
        else if(str[i]>='a' && str[i]<='z')
      	cout<<char(str[i]-32);
      	
      	// else if its a space or symbol for example just print it as is
      	else cout<<str[i];
      	
      	//the reason this works is that the distance in Ascii from uppercase to lowercase 
      	//is standard and constant
    }
    return 0;
}

How to convert lower case to upper case

$cat greekfile | tr “[a-z]” “[A-Z]”