C String strrchr() Function

What You’ll Learn

The strrchr() function finds the last occurrence of a character in a C-string. It is the reverse-direction partner of strchr()—perfect for file paths, extensions, and any task where the final match matters.

Definition and Usage

strrchr stands for string reverse char. It scans from the end of the string backward (conceptually) and returns a pointer to the last byte equal to c. Printing result with %s shows the suffix starting at that character.

Common jobs include finding the last path separator in /home/user/docs/report.pdf, the last dot before an extension, or the final delimiter in a log line.

📝 Syntax

Standard C declaration:

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

Parameters

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

Return Value

• Pointer to the last occurrence of c in str.
• NULL if c does not appear (except c == '\0', which always matches the terminator).

Header

• #include <string.h>

Examples Gallery

Compile with gcc strrchr.c -std=c11 -o strrchr. Each example checks for NULL before using the returned pointer.

#include <stdio.h>
#include <string.h>

int main(void) {
    const char *text = "Hello, C Programming!";
    char searchChar = 'o';

    char *result = strrchr(text, searchChar);

    if (result != NULL) {
        printf("Last occurrence of '%c': %s\n", searchChar, result);
    } else {
        printf("'%c' not found in the string.\n", searchChar);
    }

    return 0;
}

Last occurrence of 'o': ogramming!

#include <stdio.h>
#include <string.h>

int main(void) {
    const char *path = "/home/user/projects/main.c";

    char *slash = strrchr(path, '/');

    if (slash != NULL) {
        printf("Directory part: %.*s\n", (int)(slash - path), path);
        printf("File part:      %s\n", slash + 1);
    }

    return 0;
}

Directory part: /home/user/projects
File part:      main.c

#include <stdio.h>
#include <string.h>

int main(void) {
    const char *filename = "report.final.pdf";

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

    if (dot != NULL && dot[1] != '\0') {
        printf("Extension: %s\n", dot + 1);
    } else {
        printf("No extension found.\n");
    }

    return 0;
}

Extension: pdf

#include <stdio.h>
#include <string.h>

int main(void) {
    const char *s = "ab-cd-ef";

    char *first = strchr(s, '-');
    char *last  = strrchr(s, '-');

    printf("strchr:  %s\n", first);
    printf("strrchr: %s\n", last);

    return 0;
}

strchr:  -cd-ef
strrchr: -ef

#include <stdio.h>
#include <string.h>

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

    char *p = strrchr(word, 'z');

    if (p == NULL) {
        printf("'z' does not appear in \"%s\"\n", word);
    } else {
        printf("Found at: %s\n", p);
    }

    return 0;
}

'z' does not appear in "CodeToFun"

🚀 Common Use Cases

• File paths — find the last / or \ before the filename.
• Extensions — locate the final . in a simple filename.
• Log parsing — split at the last delimiter in a line.
• URL handling — isolate the path segment after the final slash.
• Teaching pointer views — suffix strings without copying memory.

📝 Notes

• Case-sensitive—'a' and 'A' differ.
• Return pointer points into str; do not free() it.
• strrchr(str, '\0') returns the terminator (same as end of string).
• For Windows paths, also search '\\' or normalize separators first.
• Not for binary blobs unless they are valid null-terminated C-strings.

⚡ Optimization

Standard library implementations scan at most once from the end. If you only need the string length, use strlen directly rather than strrchr(str, '\0'). For repeated searches on the same long string, cache the last known position when parsing incrementally.

💡 Best Practices