C/String/String Search

A demonstration of seeking and finding

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

void main() {

 char str1[] = "This string contains the key.";
 char str2[] = "the key";
 char str3[] = "the keys";
 if(strstr(str1, str2) == NULL)
   printf("\nString not found.");
 else
   printf("\nString: %s\n was found in string: %s",str2, str1);
 if(strstr(str1, str3) == NULL)
   printf("\nString not found.");
 else
   printf("\nWe shouldn"t get to here!");

}

      </source>

Find character in string: how to use strchr

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main () {

 char str[] = "This is a line";
 char *p;
 
 printf ("Looking for "s" character in \"%s\"...\n", str);
 
 p = strchr(str, "s");
 
 while (p != NULL) {
   printf ("found at %d\n",p - str + 1);
   p = strchr(p + 1, "s");
 }
 return 0;

}

      </source>

Finding occurrences of one string in another: strstr

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>
3. include <ctype.h>

void main() {

 char text[100];             
 char substring[40];         
 int i = 0;                  
 
 printf("\n string to be searched(less than 100 characters):\n");
 gets(text);
 
 printf("\n string sought (less than 40 characters ):\n");
 gets(substring);

 /* Convert both strings to upper case. */
 for(i = 0 ; (text[i] = toupper(text[i])) != "\0" ; i++);
 for(i = 0 ; (substring[i] = toupper(substring[i])) != "\0" ; i++);
   printf("\nThe second string %s found in the first.\n",
             ((strstr(text, substring) == NULL) ? "was not" : "was"));

}

      </source>

Find last occurrence of character in string

<source lang="cpp">

1. include <string.h>
2. include <stdio.h>

int main(void) {

 char *p;
 p = strrchr("this is a test", "i");
 printf(p);
 return 0;

}

      </source>

Find last occurrence of character in string: how to use strrchr

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main () {

 char str[] = "This is a line";
 char *p;
 
 p = strrchr(str, "i");
 printf ("Last occurence of "i" is %d \n", p - str + 1);
 
 return 0;

}

      </source>

Find substring

<source lang="cpp">

1. include <string.h>
2. include <stdio.h>

int main(void) {

 char *p;
 p = strstr("this is a test", "is");
 printf(p);
 return 0;

}

      </source>

Find substring: how to use strstr

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main () {

 char str[] ="This is a line";
 char *p;
 
 p = strstr (str, "is");
 strncpy (p, "sample",5 );
 puts (str);
 
 return 0;

}

      </source>

Find sub string: our own function

<source lang="cpp">

1. include <stdio.h>

int find_substr(char *listPointer, char *itemPointer); int main(void) {

 if(find_substr("C is fun", "is") != -1)
   printf("Substring is found.");
 return 0;

} /* Return index of first match of itemPointer in listPointer. */ int find_substr(char *listPointer, char *itemPointer) {

 int t;
 char *p, *p2;
 for(t=0; listPointer[t]; t++) {
   p = &listPointer[t];
   p2 = itemPointer;
   while(*p2 && *p2==*p) {
     p++;
     p2++;
   }
   if(!*p2) return t; /* 1st return */
 }
  return -1; /* 2nd return */

}

      </source>

Look up names in a hardcoded list

<source lang="cpp">

1. define STRING_LENGTH 80
2. include <stdio.h>
3. include <string.h>

int lookup(char const *const name); /* lookup a name */ int main() {

   char name[STRING_LENGTH] = "Jim";
   name[strlen(name)] = "\0";
   if (lookup(name)){
       printf("%s is in the list\n", name);
   }else{
       printf("%s is not in the list\n", name);
   }
   return (0);

} int lookup(char const *const name) {

   static char *list[] = {"John","Jim","Jane","Clyde",NULL};
   int index;
   for (index = 0; list[index] != NULL; ++index) {
       if (strcmp(list[index], name) == 0)
           return (1);
   }
   return (0);

}

      </source>

Scan string for specified characters

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main(void) {

 char *p;
 p = strpbrk("this is a test", " absj");
 printf(p);
 return 0;

}

      </source>

Scan string for specified characters: how to use strpbrk

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main () {

 char str[] = "This is a line";
 char key[] = "aeiou";
 char *p;
 printf ("Vowels in "%s": ",str);
 p = strpbrk (str, key);
 while (p != NULL) {
 
   printf ("%c " , *p);
   p = strpbrk (p + 1, key);
 
 }
 printf ("\n");
 
 return 0;

}

      </source>

Search a char inside a string

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main(void) {

 char *p;
 p = strchr("this is a test", " ");
 printf(p);
 return 0;

}

      </source>

Search string

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int search(char *p[], char *name); char *names[] = {"John","Jim","Jane","James",NULL}; int main(void) {

 if(search(names, "James") != -1)
   printf("in list.\n");
 if(search(names, "Bill") == -1)
   printf("not found.\n");
 return 0;

} int search(char *p[], char *name) {

 int t;
 for(t=0; p[t]; ++t){
   if(!strcmp(p[t], name)) {
      return t;
   }
 }
   return -1; /* not found */

}

      </source>

Search string for occurrence of character set

<source lang="cpp">

1. include <string.h>
2. include <stdio.h>

int main(void) {

 int len;
 len = strcspn("this is a test", "ab");
 printf("%d", len);
 return 0;

}

      </source>

Search string for occurrence of character set: how to use strcspn

<source lang="cpp">

1. include <stdio.h>
2. include <string.h>

int main () {

 char str1[] = "1245789000";
 char str2[] = "1234567890";
 int i;
 i = strcspn (str1,str2);
 printf ("The first number in str1 is str1[%d]\n", i);
 return 0;

}

      </source>