#include <stdio.h>
#include <stdlib.h>		// includes NULL==0
#include <string.h>

int main(int argc, char *argv[])
{
    // argc is count, includes program name
    // argv[0] is program name

    // print arguments in reverse order
    int i;
    for (i = argc - 1; i > 0; i--)
	puts(argv[i]);

    char *suits[] = { "Hearts", "Spades", "Diamonds", "Clubs" };
    for (i = 0; i < 4; i++)
	printf("%d %s\n", strlen(suits[i]), suits[i]);


    char *s1 = "string 1";
    puts(s1);

    char *s2;
    s2 = "string 2";
    puts(s2);

// char s3[];
    char s3[100];		// must have size
//      s3 = "string 3";        // not compatible types
    s3[0] = 's';
    s3[1] = 't';
    s3[2] = '\0';
    s3[3] = '*';
    s3[99] = '$';
    puts(s3);			// st

//      s3 = s1;        // s3 is constant
    s2 = s1;
//      s2[0] = 'P';    // seg fault
//      *s2 = 'P';      // seg fault
// can't change contents of string if allocated as literal
    printf("%p %s\n", s2, s2);
    printf("%p %s\n", s1, s1);

    s2 = s3;			// point to same memory array
    s2[0] = '*';
    printf("%p %s\n", s2, s2);
    printf("%p %s\n", s3, s3);

    char s4[] = "string 4";
    puts(s4);
    //      s4 = s1;  // incompatible types
    s4[0] = '*';

// strcpy(to, from) - up to you that to is big enough to hold from
    strcpy(s3, s4);
    puts(s3);

/* doesn't work because s5 doesn't point to any memory
	char *s5;
	strcpy(s5, s4);
	puts(s5);
*/

    char *s5 = "l;skdj fowiealskdjfg;oiewasd";
//      strcpy(s5, s4); // seg fault because s5 memory immutable
    puts(s5);

    char s6[strlen(s4) * 2 + 1];
    strcpy(s6, s4);
    puts(s6);
    strcat(s6, s4);
    puts(s6);

/*
	char *s7 = NULL;
	gets(s7);		// seg fault because s7 is NULL
*/
    char *s7;			// random junk value
//      gets(s7);  // causes compiler warning because unsafe
// also causes seg fault when run
//      puts(s7);       // seg fault 
//      printf("%p\n", s7);
    s7 = "s7 init";
    puts(s7);

    char s8[10];
    puts("enter string: ");
    fgets(s8, 10, stdin);	// safe way, reads 9 chars or less, puts in \0
    puts(s8);

    strcat(s8, "hello");
    puts(s8);

/* other string functions
in string.h
char *strcpy(char *to, const char *from)
char *strcat(char *to, const char *from)
int strlen(const char *s)
int strcmp(const char *s1, const char *s2)

in stdio.h
puts(s)
fgets(s,SIZE,stream)

in stdlib.h
double atof(const char *s)
int atoi(const char *s)
double strtod(const char *s, char **endp)

*/
    char *line = "   123.45 other stuff";
    char *s;
    double d;
    d = strtod(line, &s);
    printf("d=%f s=%s line=%s\n", d, s, line);

    int month = 0, day = 0, year = 0;
    char *date = "4/23/2010";
    const char *DELIM = "/ ";	// use '/' and ' ' (space) to break apart
    char *token;
//      token = strtok(date,DELIM);  // can't use on string literals
    // because strtok changes the original string

    char dateVar[11];
    strcpy(dateVar, date);	// copy from literal date to variable

    printf("dateVar before month taken: %s\n", dateVar);
    token = strtok(dateVar, DELIM);
    month = atoi(token);
    printf("dateVar after month taken: %s\n", dateVar);
    day = atoi(strtok(NULL, DELIM));
    year = atoi(strtok(NULL, DELIM));
    printf("%d-%d-%d\n", month, day, year);
    printf("%02d-%02d-%04d\n", month, day, year);

    return 0;
}