C++ String strrchr() Function

What You’ll Learn

The strrchr() function scans a C-string from start to end and returns a pointer to the last occurrence of a given character. Where strchr() finds the first match, strrchr() finds the final one—ideal for file extensions, trailing path separators, and the rightmost delimiter in a line.

Definition and Usage

In C++, strrchr() is declared in <cstring>. It walks the entire null-terminated string and remembers the most recent position where the target character appeared. When the scan finishes, it returns that address or nullptr if the character never occurred.

The second parameter is typed as int but holds a character value such as '/' or '.'. The returned pointer points into the original string—no new memory is allocated.

📝 Syntax

Function signature and a typical call:

#include <cstring>

char* strrchr(const char* str, int character);

// Example:
const char* lastO = strrchr("Hello, C++ programming!", 'o');
// index == 13 when lastO is not nullptr

Parameters

• str — null-terminated C-string to search.
• character — character to find, passed as an int (e.g. 'o').

Return Value

Pointer to the last matching character in str, or nullptr if the character is absent.

Examples Gallery

Compile with g++ strrchr.cpp -std=c++17 -o strrchr. Always verify the return pointer is not nullptr before using it.

#include <iostream>
#include <cstring>

int main() {
    const char* sentence = "Hello, C++ programming!";

    const char* lastO = std::strrchr(sentence, 'o');

    if (lastO != nullptr) {
        std::cout << "Last 'o' at index: " << (lastO - sentence) << "\n";
        std::cout << "Character:       " << *lastO << "\n";
    } else {
        std::cout << "'o' not found.\n";
    }

    return 0;
}

Last 'o' at index: 13
Character:       o

#include <iostream>
#include <cstring>

int main() {
    const char* filename = "tutorial.final.cpp";

    const char* dot = std::strrchr(filename, '.');

    if (dot != nullptr) {
        std::cout << "Base:      ";
        for (const char* p = filename; p != dot; ++p) {
            std::cout << *p;
        }
        std::cout << "\nExtension: " << (dot + 1) << "\n";
    }

    return 0;
}

Base:      tutorial.final
Extension: cpp

#include <iostream>
#include <cstring>

int main() {
    const char* path = "/home/user/docs/report.pdf";

    const char* firstSlash = std::strchr(path, '/');
    const char* lastSlash  = std::strrchr(path, '/');

    std::cout << "First '/':  index " << (firstSlash - path) << "\n";
    std::cout << "Last '/':   index " << (lastSlash - path) << "\n";
    std::cout << "Filename:   " << (lastSlash + 1) << "\n";

    return 0;
}

First '/':  index 0
Last '/':   index 15
Filename:   report.pdf

#include <iostream>
#include <cstring>

int main() {
    const char* fullPath = "C:/projects/cpp/strrchr.cpp";

    const char* slash = std::strrchr(fullPath, '/');
    if (slash == nullptr) {
        slash = std::strrchr(fullPath, '\\');
    }

    if (slash != nullptr) {
        std::cout << "Directory: ";
        for (const char* p = fullPath; p != slash; ++p) {
            std::cout << *p;
        }
        std::cout << "\n";
    }

    return 0;
}

Directory: C:/projects/cpp

#include <iostream>
#include <cstring>

int main() {
    const char* word = "strrchr";

    const char* atSign = std::strrchr(word, '@');

    if (atSign == nullptr) {
        std::cout << "No '@' in \"" << word << "\"\n";
    } else {
        std::cout << "Found '@' at " << (atSign - word) << "\n";
    }

    return 0;
}

No '@' in "strrchr"

🚀 Common Use Cases

• File extensions — locate the last dot in a filename.
• Path parsing — find the final slash or backslash before the basename.
• Trailing delimiters — split on the last comma or semicolon in a line.
• Log analysis — find the last colon in a timestamp or level prefix.
• Pairing with strchr() — first and last bounds of a substring region.

📝 Notes

• The returned pointer aliases memory inside str—valid only while that buffer lives.
• The search character is an int; char literals like '/' work directly.
• Case-sensitive: 'A' and 'a' are different targets.
• Passing '\0' finds the string terminator (advanced edge case).
• For std::string, prefer s.rfind('.') instead of strrchr(s.c_str(), '.').

⚡ Optimization

strrchr() always scans the full string once, even if the last match is near the end. For very long strings searched repeatedly, consider scanning backwards manually or caching parsed path components. Library implementations are typically optimized for common cases.

💡 Best Practices