CSE 2031 Lecture 4

Strings

• strlen(s)
  
  • returns length
    
• strcmp(s,t)
  
• returns positive if s>t, negative if s<t, and 0 if they are equal.
  
• strcat(s,t)
  
  • concatenates t onto s
    
    • changes string s
      
  • looks or \o and contatenates at that spot
    

#include <stdio.h>

Int main(void)

{

char s1[] = {'H','e','l','l','o','\o'};

char s2[4];

printf("Address of s1 is %p\n", s1);

printf("address of s2 is %p\n", s2);

printf("Enter a line: ");

fgets(s2, sizeof(s2), stdin);/* bolded represent extras for using fgets*/

printf("%s\n", s2);

printf("%s\n", s1);

return 0;

}

 

• Fgets is the new one that works better, if you use just gets you will run into problems with memory over runs
  
• Where s1 in this example can be overwritten by s2 if the user input is long enough
  
• Look up input and output in textbook
  
• With fgets it will only take in the amount of characters assigned after the first comma
  
• However if less than the specified amount is passed and the enter key is pushed, the new line character will count as 1 char
  

Pointers

int n = 5;

int *p;

p = &n

printf("%d\n", *p);

printf("%d\n", n);

 

 

• *p = 7;
  
  • Changes whatever value P was addressing to 7
    

If n = 5, and you said this before printing, it would print 7