C program to sort items given as input arguments

sortArguments.c

#include "stdlib.h"
#include "stdio.h"
#include "string.h"

/*
 * Returns a string containing each argument separated by a newline.
 */
char* parse_args(int argc, char** argv) {
    int char_count = 0;
    for (int i = 1; i < argc; i++) {
       char_count += (strlen(argv[i]) + 1);
    }
    char* format = (char*) malloc(char_count * sizeof(char));
    char* format_index = format;
    for (int i = 1; i < argc; i++) {
        char* str = argv[i];
        strcpy(format_index, str);
        format_index += strlen(str);
        if (i < argc - 1) {
            *(format_index++) = '\n';
        } else {
            *format_index = '\0';
        }
    }
    return format;
}

/*
 * Takes the input arguments and sorts them, removing duplicates,
 * printing the output to the screen.
 */
int main(int argc, char** argv) {
    char* input = parse_args(argc, argv);
    char* command_format = "echo \"%s\" | sort -u";
    char command[strlen(input) + strlen(command_format) - 2];
    sprintf(command, command_format, input);

    return system(command);
}

I wrote this because I hadn't done anything in C for a while and I wanted to see if I still remembered how to work with pointers and arrays. The actual sorting is on lines 34-38, and isn't the point of this code.