How to scan a string for specific terms - c

Question

I'm trying to scan user input text for specific words and then, when those words occur, print them to the console.
#import <Foundation/Foundation.h>
#include <stdio.h>
int main(){
char cArray[] = "example";
char cInput[] = "";
char cOutput[] = "";
printf("\nType your message:\n");
for (int y=0; y<1; y++){
fgets(cInput, 120, stdin);
}
printf("\nInitialised character array:\n");
for (int x=0; x<1; x++){
if(strncmp(&cInput[x], &cArray[x], 120) == 0){
strncpy(cOutput, cArray, strnlen(cInput, +1));
printf("%s\n", cOutput);
break;
}
}
}
Output:
Type your message:
example
Initialised character array:
Program ended with exit code: 120
Appreciate any feedback as I'm still learning :)
Thanks.
The edited code:
#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++;
}
}
}
Works although I'm encountering a different problem now. The output only seems to register one word before it completes, thus only "example" is printed.
Output:
Type your message:
this is an example
Initialised string array:
example
Program ended with exit code: 0

Answer 1

char cInput[] = "";
The sizeof this array is 1.
fgets(cInput, 120, stdin);
This is array out of bound write which will lead to undefined behavior.
Have
char cInput[120] = "";
You need to take care of
char cOutput[120] = "";
also. Since you are trying to write to this array after comparing.

Answer 2

You need strstr function from string.h
const char * strstr ( const char * str1, const char * str2 );
the following gives you an example of usage:
#include <stdio.h>
#include <string.h>
#define MAX_STR_LEN 120
int main(){
char cArray[MAX_STR_LEN] = "example"; // string to be searched in the input string
char cInput[MAX_STR_LEN] = ""; // input string
char cOutput[MAX_STR_LEN] = ""; // buffer for found string
printf("\nType your message:\n");
for (int y=0; y<1; y++){ // this loop from original example looks strange, but it works
fgets(cInput, MAX_STR_LEN, stdin);
}
// search in the input string
char * ptr;
if( ( ptr=strstr(cInput, cArray) ) != NULL)
{
//copy the string to cOutput
strncpy(cOutput, ptr, strlen(cArray));
// output the found string
printf("String that was found: \n%s\n", cOutput);
}
else
{
printf("String was not found in the input!\n");
}
}
EDIT:
If you want to all the strings, use the following loop instead of if-else:
// search in the input string
char * ptr = cInput;
while( ( ptr=strstr(ptr, cArray) ) != NULL)
{
//copy the string to cOutput
strncpy(cOutput, ptr, strlen(cArray));
// output the found string
printf("String \"%s\" was found at position %d\n", cOutput, (int)(ptr - cInput + 1));
// find next string
ptr++;
}