exercise7-1.md

Exercise 7-1

Write a program that converts upper case to lower or lowercase to upper, depending on the name it is invoked with, as found in argv[0].

Process

Very straightforward exercise, I was expecting something more complicated ha. Kind of a fun idea to change functionality based on the name of the program. Could be a cool hidden feature in a game.

Being on windows, the program checks for the name and for .exe extension.

Used a function pointer because it felt like an appropriate use case.

Used symbolic links to change argv[0].

Found the answers on clc-wiki to be maybe too complicated? I liked the simplicity of the answer in the C Answers Book.

Code

#include <stdio.h>
#include <ctype.h>
#include <string.h>

int main(int argc, char *argv[])
{
    int c, (*convert)(int c) = NULL;
    
    if ((strcmp(*argv,"lower") == 0) || (strcmp(*argv,"lower.exe") == 0))
        convert = tolower;
    else if ((strcmp(*argv,"upper") == 0) || (strcmp(*argv,"upper.exe") == 0))
        convert = toupper;
    
    if (convert == NULL) {
        while ((c = getchar()) != EOF)
            putchar(c);
    } else {
        while ((c = getchar()) != EOF)
            putchar(convert(c));
    }
    
    return 0;
}

Output

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