man strstr

The strstr function in C is used to find the first occurrence of a substring within a string. It searches for the substring in the given string and returns a pointer to the first occurrence of the substring, or NULL if the substring is not found.

Here are the steps involved in the strstr function:

  1. The strstr function takes two arguments: the source string and the substring to search for.

  2. It starts by comparing the first character of the substring with each character in the source string.

  3. If the first character of the substring matches a character in the source string, it begins comparing subsequent characters of the substring with the corresponding characters in the source string.

  4. If all characters of the substring match the corresponding characters in the source string, the strstr function returns a pointer to the first occurrence of the substring within the source string.

  5. If the substring is not found, the strstr function returns NULL.

  6. It's important to note that the strstr function is case-sensitive, meaning it treats uppercase and lowercase characters as different. So, if the case of characters doesn't match exactly, the function will not consider it a match.

  7. Additionally, the strstr function only finds the first occurrence of the substring within the source string. If you need to find all occurrences, you would need to implement a loop or use other functions like strtok or strpbrk.

That's a brief overview of the strstr function in C and the steps involved in its execution.