First occurrence return with strstr function - c

Question

Following on from my previous question, it now appears that my code only outputs the first occurrence of cArray from cInput. Is there a way to get strstr to return all of the occurrences instead of stopping the program at the first? Much appreciated.
#include <stdio.h>
#include <string.h>
#define MAX_STR_LEN 120
int main(){
char *cArray[MAX_STR_LEN] = {"example", "this"};
char cInput[MAX_STR_LEN] = "";
char cOutput[MAX_STR_LEN] = "";
printf("Type your message:\n");
for (int y=0; y<1; y++){
fgets(cInput, MAX_STR_LEN, stdin);
char * ptr = cInput;
while((ptr=strstr(ptr, *cArray)) != NULL){
strncpy(cOutput, ptr, strlen(*cArray));
printf("Initialised string array:\n%s\n", cOutput);
ptr++;
}
}
}
Output:
Type your message:
this is an example
Initialised string array:
example
Program ended with exit code: 0
Edited code:
#include <stdio.h>
#include <string.h>
#define MAX_STR_LEN 120
int main() {
char *cArray[MAX_STR_LEN] = { "example", "this", "is", "an" };
char cInput[MAX_STR_LEN] = { 0 };
int y = 0;
printf("Type your message:\n");
fgets(cInput, MAX_STR_LEN, stdin);
cInput[strlen(cInput) - 1] = 0; /* strip newline from input */
printf("\nInitialised string array:\n");
while (cArray[y])
{
char * ptr = cInput;
while ((ptr = strstr(ptr, cArray[y])) != NULL)
{
char *ep = strchr (ptr, ' ');
if (ep) *ep = 0; /* null-terminate at space */
printf("%s\n", ptr++);
if (ep) *ep = ' '; /* put the space back */
}
y++;
}
return 0;
}
New output:
Type your message:
this is an example
Initialised string array:
example
this
is
is
an
Program ended with exit code: 0

Answer 1

here is the corrected program:
#include <stdio.h>
#include <string.h>
#define MAX_STR_LEN 120
int main(){
char *cArray[MAX_STR_LEN] = { "example", "this" };
char cInput[MAX_STR_LEN] = "";
char cOutput[MAX_STR_LEN] = "";
printf("Type your message:\n");
fgets(cInput, MAX_STR_LEN, stdin);
printf("Initialised string array:\n");
for (int y = 0; y <= 1; y++){
char * ptr = cInput;
while ((ptr = strstr(ptr, cArray[y])) != NULL){
strncpy(cOutput, ptr, strlen(cArray[y]));
printf("[%d] - %s\n", y, cOutput);
memset(cOutput, 0, sizeof(cOutput));
ptr++;
}
}
getchar();
return 0;
}
Changes:
Used memset to reset the cOutput array so that during comparison
in the next iteration, it was empty.
Used the index y to keep track of each word from the array
Chagned array range from y<1 to y<=1

Answer 2

In addition to the other answers, here is a variation that eliminates intermediate variables and rearranges the loop logic slightly. There are many ways to approach the issue of returning all occurrences of strstr matches, so you have flexibility to use any manner that fits your needs:
#include <stdio.h>
#include <string.h>
#define MAX_STR_LEN 120
int main() {
char *cArray[MAX_STR_LEN] = { "example", "this" };
char cInput[MAX_STR_LEN] = { 0 };
int y = 0;
printf("Type your message:\n");
fgets(cInput, MAX_STR_LEN, stdin);
cInput[strlen(cInput) - 1] = 0; /* strip newline from input */
while (cArray[y])
{
char * ptr = cInput;
while ((ptr = strstr(ptr, cArray[y])) != NULL)
printf("\nInitialised string array:\n%s\n", ptr++);
y++;
}
return 0;
}
output:
alchemy:~/dev/src-c/tmp> ./bin/strstrmulti
Type your message:
my example of this example for fun
Initialised string array:
example of this example for fun
Initialised string array:
example for fun
Initialised string array:
this example for fun
To isolate only the word matching in cArray, you can use strchr to test if a space remains in the input string following the pointer returned the strstr. If so, just null-terminate the string where the next space appears which will isolate just the searched for word. If I misunderstood the comment, just leave another, I'm happy to help. (code changes only)
while (cArray[y])
{
char * ptr = cInput;
while ((ptr = strstr(ptr, cArray[y])) != NULL)
{
char *ep = strchr (ptr, ' ');
if (ep) *ep = 0; /* null-terminate at space */
printf("\nInitialised string array:\n%s\n", ptr++);
if (ep) *ep = ' '; /* put the space back */
}
y++;
}
isolated output:
alchemy:~/dev/src-c/tmp> ./bin/strstrmulti
Type your message:
my example of this example for fun
Initialised string array:
example
Initialised string array:
example
Initialised string array:
this
Here is a bit of code to look at whole words only using the inch-worm method. I haven't had a lot of time to look at all potential gotchas, but this should get you going. Just replace the code in your last version:
while (cArray[y])
{
char *ptr = cInput;
char *ep = NULL;
while ((ep = strchr (ptr, ' '))) /* set end-pointer to each space in input */
{
*ep = 0; /* null-terminate and compare word */
if (strcmp (ptr, cArray[y]) == 0)
printf("\nInitialised string array:\n%s\n", ptr);
*ep = ' '; /* restore space in string */
ptr = ++ep; /* set pointer to next char after space */
}
if (strcmp (ptr, cArray[y]) == 0) /* compare last word in input */
printf("\nInitialised string array:\n%s\n", ptr);
y++;
}
output w/updated cArray
alchemy:~/dev/src-c/tmp> ./bin/strstrmulti
Type your message:
this is an example to test the example for fun
Initialised string array:
example
Initialised string array:
example
Initialised string array:
this
Initialised string array:
is
Initialised string array:
an