String-Case.c

/* string-case.c */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <string.h>

void helpMessage(){
    printf("usage: ./string-case [-luh] <<< <String>\n");
    printf("-l Convert to lower case\n");
    printf("-u Convert to upper case\n");
    printf("-h Print help message\n");
}

void stringMod(char c,char *string){
    for(int i = 0; i < strlen(string); i++)
    {
        if(c == 'l'){
            putchar(tolower(string[i]));
        }
        if(c == 'u'){
            putchar(toupper(string[i]));
        }
    }
            printf("\n");
}

int
main(int argc, char *argv[])
{
int c; //Switch Controller
int o = -2; //Used to check if no option was provided, will print help message
char string[100];

    while ( (c = getopt (argc, argv, ":hul")) != -1)
    {
        switch (c)
        {
            case 'h':
                helpMessage();
            break;
            case 'l':
                gets(string);
                stringMod('l', string);
            break;
            case 'u':
                gets(string);
                stringMod('u', string);
            break;

        }
        o = 0;
    }
    if (o == -2){
        helpMessage(); //prints help message if no option was chosen
    }
return 0;
}