Thread: strstr Function: Search and Replacing New String

LOOK!

Code:

#include<stdio.h>
#include<string.h>
#define MAX 25

int main(void)
{   
    int ch;
    
    char *str[] = {
                  "You Know",
                  "That i learning programming",
                  "Because im interested",
                  "And its cool",
                  "When i get confused for debugging",
                  "After i succeed, i feel relieved",
                  "So i will learning and using it",
                  "Even i have no life"
                  };
    
    int i;
    char str1[MAX];
    char str2[MAX];
    char *strloc;
    
       printf("%s",str[3]);
       printf("\nNow Choose Available String in [3]:\n");
       fgets(str1,MAX,stdin);
       printf("Then Insert The New String:\n");
       fgets(str2,MAX,stdin);
       
       char *p1,*p2;
       if ((p1 = strchr(str1,'\n')) != NULL) *p1 = '\0';
       if ((p2 = strchr(str2,'\n')) != NULL) *p2 = '\0';
       
       strloc = strstr(str[3],str1);
       strncpy(strloc,str2,strlen(str2));
       
       while((ch = getchar()) != '\n' && ch != EOF);
       getchar();
       return 0;
}

this is from exercise Let Us C book i get from online
the objective located the available string in line and replacing with other string
Example:
char str[5] = "After i succeed, i feel relieved";
if "succeed" string is replacing with new string like "failed"
the new line has to be
char str[5] = "After i failed, i feel relieved";

im surfing the internet c string reference and i got the wonderful function in string.h that is
strstr() function
which located the same string and with
strncpy() function
the string will changed

but seems strstr() function must using string constant (i use *strloc) in this case.

that's the problem
i get confused with line

strloc = strstr(str[3],str1)

str[3] was a string constant based on array, the declaration are *str[] which related to multidimensional array.

i think that cause this program to be error.
because when i using the reference from internet, the program was executed for sure.
This code what i mean

Code:

#include <stdio.h>
#include <string.h>
#define MAX 10

int main ()
{
  int ch;
  char str[] ="This is a simple string";
  char str1[MAX];
  char str2[MAX];
  
  printf("Insert The Same String:\n");
  fgets(str1,MAX,stdin);
  printf("Insert The Replacing String:\n");
  fgets(str2,MAX,stdin);
  
  char *p1,*p2;
  if ((p1 = strchr(str1,'\n')) != NULL) *p1 = '\0';
  if ((p2 = strchr(str2,'\n')) != NULL) *p2 = '\0';
  
  char *pch;
  pch = strstr(str,str1);
  strncpy (pch,str2,strlen(str2));
  puts(str);
  
  while((ch = getchar()) != '\n' && ch != EOF);
  getchar();
  return 0;
}

and rather than that i didnt have anymore idea to make that replacing string.
anyhelp will appreciated
Thank You!

PS: This is only exercise for me, not a homework, so lets discuss this matter if u want to

this is from exercise Let Us C book i get from online

I guess that explains why it's so terrible. Try reading K&R2.

im surfing the internet c string reference and i got the wonderful function in string.h that is
strstr() function
which located the same string and with
strncpy() function
the string will changed

You can implement strstr with strncpy or without it.

but seems strstr() function must using string constant (i use *strloc) in this case.

The 'const's that appear in strstr's parameter list simply guarantee that strstr won't modify any elements through either of the pointers you pass. You don't need to make your own types const -- they'll be converted to the correct pointer type automatically when you make the call.

I guess that explains why it's so terrible. Try reading K&R2.

why terrible? let us c book is bad ?

The 'const's that appear in strstr's parameter list simply guarantee that strstr won't modify any elements through either of the pointers you pass. You don't need to make your own types const -- they'll be converted to the correct pointer type automatically when you make the call.

yeah, on a minute before i reading your reply, i realize that string constant cannot be changed or modified, i guess i will passing all string *str[] into the new array string like this.

char ss[MAX];
int i;
for(i = 0; i < 7; i++)
ss = str[i];

but it still had weakness just by looking at it

why terrible? let us c book is bad ?

Sure is.

You know you can't assign to arrays right?

String, String, why don't you give me a call?
String, String, the happiest sound of them all
String, String, I stare at the phone on the wall
And I sit all alone impatiently
Won't you please understand the need in me
So, String, String, why don't you give me a call?
So, String, String, why don't you give me a call?

i would say swing swing rather than string - string