Thread: How to use "strstr" to find all occurrences of a substring in a string not only first

Hello guys.
Im having troubles with the "strstr" function.

Im trying to count the number of times a substring appears in a string.
For this im using the STRSTR function but that function returns only the first occurrence of a substring in a string.

So if I use STRSTR to count the number of times the word "par" appears in "parparpar" it will return 1 because after the first occurrence, the function stops.

The code im using is this:

Code:

int countPar(char str[256])
{
int total;
if (strstr(str, "par")!=NULL) // finds "par" in string
total++;
return total;    
}

That function always returns 1.

I want it to return 3 if I use "parparpar" as str.

All I want is to know the number of times a substring appears in a string.

THANKS!!!!!!

Code:

char *p = str;
while ( strstr(p,"par") != NULL ) {
  p++; // can you improve this?
  total++;
}

Salem thanks but its not working, I tried your code but its not returning what it should.
For the code below, it returns 4 instead of 2.

Thanks for your help, waiting for more answers if possible.

Code:

int main()
{
int total=0;
char *p="parpar";
while ( strstr(p,"par") != NULL ) 
   {
printf("%s", p); // to know the content of p
p++;
total++;
   }
printf("%i", total);
getch(); // pause
}

while ( (p=strstr(p,"par")) != NULL )

It works now, perfectly.
Full code:

Code:

int main()
{
char *p="parparpar";
int total=0;
while ( (p=strstr(p,"par")) != NULL )
  {
total++;
p++;
  }
printf("%i", total); // prints 3 as it should
getch();
}

Thanks for your help.

Originally Posted by Salem

Code:

char *p = str;
while ( strstr(p,"par") != NULL ) {
  p++; // can you improve this?
  total++;
}

Just an idea to improve this piece of code:

Code:

char *p = str;
while ( strstr(p,"par") != NULL ) {
  p += strlen(p);
  total++;
}

Did you know p += strlen(p) always ends up pointing at the \0 ?

Ok really bored:

Code:

#include <stdio.h>

int main()
{
        const char *haystack =
        "Is this the real life-\n"
        "Is this just fantasy-\n"
        "Caught in a landslide-\n"
        "No escape from reality-\n"
        "Open your eyes\n"
        "Look up to the skies and see-\n"
        "I.m just a poor boy,i need no sympathy-\n"
        "Because I.m easy come,easy go,\n"
        "A little high,little low,\n"
        "Anyway the wind blows,doesn.t really matter to me,\n"
        "To me\n"
        "Mama,just killed a man,\n"
        "Put a gun against his head,\n"
        "Pulled my trigger,now he.s dead,\n"
        "Mama,life had just begun,\n"
        "But now I.ve gone and thrown it all away-\n"
        "Mama ooo,\n"
        "Didn.t mean to make you cry-\n"
        "If I.m not back again this time tomorrow-\n"
        "Carry on,carry on,as if nothing really matters-\n"
        "Too late,my time has come,\n"
        "Sends shivers down my spine-\n"
        "Body.s aching all the time,\n"
        "Goodbye everybody-I.ve got to go-\n"
        "Gotta leave you all behind and face the truth-\n"
        "Mama ooo- (any way the wind blows)\n"
        "I don.t want to die,\n"
        "I sometimes wish I.d never been born at all-\n"
        "I see a little silhouetto of a man,\n"
        "Scaramouche,scaramouche will you do the fandango-\n"
        "Thunderbolt and lightning-very very frightening me-\n"
        "Galileo,galileo,\n"
        "Galileo galileo\n"
        "Galileo figaro-magnifico-\n"
        "But I.m just a poor boy and nobody loves me-\n"
        "He.s just a poor boy from a poor family-\n"
        "Spare him his life from this monstrosity-\n"
        "Easy come easy go-,will you let me go-\n"
        "Bismillah! no-,we will not let you go-let him go-\n"
        "Bismillah! we will not let you go-let him go\n"
        "Bismillah! we will not let you go-let me go\n"
        "Will not let you go-let me go\n"
        "Will not let you go let me go\n"
        "No,no,no,no,no,no,no-\n"
        "Mama mia,mama mia,mama mia let me go-\n"
        "Beelzebub has a devil put aside for me,for me,for me-\n"
        "So you think you can stone me and spit in my eye-\n"
        "So you think you can love me and leave me to die-\n"
        "Oh baby-can.t do this to me baby-\n"
        "Just gotta get out-just gotta get right outta here-\n"
        "Nothing really matters,\n"
        "Anyone can see,\n"
        "Nothing really matters-,nothing really matters to me,\n"
        "Any way the wind blows....";
        const char *needle = "poor";
        unsigned total = 0;
        const char *p = haystack;
        while ( (p=strstr(p,needle)) != NULL ) {
                p += strlen(needle);
                total++;
        }
        printf("%u occurences of %s\n", total, needle);
        return 0;
}

How many occurences of "harhar" are in "harharharharharhar"?

Originally Posted by SlyMaelstrom

Even though that reply was meant to be trivial, it made me consider that some might say 3 and some might say 5.

Yes, that was my point, and to illustrate the simple += strlen(needle) technique may produce unwanted results.