Question

How to remove file extension in C

Answer 1

#include <stdio.h>
#include <string.h>
 
/*
 * Removes the last file extension from a path or filename.
 *
 * Examples:
 *   "document.pdf"      -> "document"
 *   "archive.tar.gz"    -> "archive.tar"
 *   "photo.jpg"         -> "photo"
 *   "README"            -> "README"
 *   "/tmp/file.txt"     -> "/tmp/file"
 *
 * Parameters:
 *   filename     Input filename or path.
 *   output       Output buffer.
 *   outputSize   Size of output buffer.
 *
 * Returns:
 *   0 on success.
 *  -1 on error.
 */
int removeFileExtension(
    const char *filename,
    char *output,
    size_t outputSize)
{
    const char *dot;
    const char *slash1;
    const char *slash2;
    const char *lastSeparator;
    size_t length;
 
    if (filename == NULL || output == NULL || outputSize == 0) {
        return -1;
    }
 
    /* Copy original string safely. */
    strncpy(output, filename, outputSize - 1);
    output[outputSize - 1] = '\0';
 
    /* Find the last dot. */
    dot = strrchr(output, '.');
 
    /* Find the last path separator. */
    slash1 = strrchr(output, '/');
    slash2 = strrchr(output, '\\');
 
    lastSeparator = slash1;
 
    if (slash2 != NULL &&
        (lastSeparator == NULL || slash2 > lastSeparator))
    {
        lastSeparator = slash2;
    }
 
    /*
     * Remove the extension only if the dot belongs
     * to the filename and is not part of a directory.
     */
    if (dot != NULL &&
        (lastSeparator == NULL || dot > lastSeparator))
    {
        * (char *)dot = '\0';
    }
 
    length = strlen(output);
 
    return (length < outputSize) ? 0 : -1;
}
 
int main(void)
{
    const char *filename = "archive.tar.gz";
    char result[256] = "";
 
    if (removeFileExtension(filename, result, sizeof(result)) == 0) {
        printf("Original: %s\n", filename);
        printf("Without extension: %s\n", result);
    }
    
    if (removeFileExtension("document.pdf", result, sizeof(result)) == 0) {
        printf("Original: %s\n", "document.pdf");
        printf("Without extension: %s\n", result);
    }

    if (removeFileExtension("README", result, sizeof(result)) == 0) {
        printf("Original: %s\n", "README");
        printf("Without extension: %s\n", result);
    }

    if (removeFileExtension("/tmp/file.txt", result, sizeof(result)) == 0) {
        printf("Original: %s\n", "/tmp/file.txt");
        printf("Without extension: %s\n", result);
    }
 
    return 0;
}
 

/*
run:

Original: archive.tar.gz
Without extension: archive.tar
Original: document.pdf
Without extension: document
Original: README
Without extension: README
Original: /tmp/file.txt
Without extension: /tmp/file

*//

 

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Answer 2

#include <stdio.h>
#include <string.h>
 
/*
 * Removes the last file extension from a path or filename.
 *
 */
/*
 * Removes the last extension from a filename in place.
 */
void removeFileExtension(char *filename)
{
    char *dot = strrchr(filename, '.');
 
    if (dot != NULL) {
        *dot = '\0';
    }
}
 
int main(void)
{
    char filename[]  = "archive.tar.gz";
 
    removeFileExtension(filename);
    printf("Without extension: %s\n", filename);

    strcpy(filename, "document.pdf");
    removeFileExtension(filename);
    printf("Without extension: %s\n", filename);
    
    strcpy(filename, "README");
    removeFileExtension(filename);
    printf("Without extension: %s\n", filename);

    strcpy(filename, "/tmp/file.txt");
    removeFileExtension(filename);
    printf("Without extension: %s\n", filename);
 
    return 0;
}
 
 

/*
run:

Without extension: archive.tar
Without extension: document
Without extension: README
Without extension: /tmp/file

*/

 

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