This is a mirror of my library hosted at https://create.stephan-brumme.com/practical-string-searching/

There is a huge number of scientific papers on fast, faster and super-fast string searching algorithms. They usually prove theoretical performance in O-Notation and most papers cover memory consumption as well.

However, theoretical performance isn't always the same as practical performance. That's why I always want to measure real-world throughput: this article presents hopefully understandable C implementations of the most common generic string search algorithms.

In addition I also wrote a simple tool called mygrep that prints all lines of a file where a search phrase is found. It doesn't come with all the bells and whistles of the Unix tool grep but achieves similar or sometimes even better speed.

• simple loop / brute force
• memchr/memcmp
• memmem
• strstr
• Knuth-Morris-Pratt
• Boyer-Moore-Horspool
• Bitap aka Baeza-Yates-Gonnet
• Rabin-Karp

All C functions share the same interface: const char* search(const char* haystack, const char* needle); for strings const char* search(const char* haystack, size_t haystackLength, const char* needle, size_t needleLength); for binary data

See my website https://create.stephan-brumme.com/practical-string-searching/ for a live demo, code examples and benchmarks.