Getting absolute path of a file

Use realpath().

The realpath() function shall derive, from the pathname pointed to by file_name, an absolute pathname that names the same file, whose resolution does not involve '.', '..', or symbolic links. The generated pathname shall be stored as a null-terminated string, up to a maximum of {PATH_MAX} bytes, in the buffer pointed to by resolved_name.

If resolved_name is a null pointer, the behavior of realpath() is implementation-defined.

The following example generates an absolute pathname for the file identified by the symlinkpath argument. The generated pathname is stored in the actualpath array.

#include <stdlib.h>...char *symlinkpath = "/tmp/symlink/file";char actualpath [PATH_MAX+1];char *ptr;ptr = realpath(symlinkpath, actualpath);

Try realpath() in stdlib.h

char filename[] = "../../../../data/000000.jpg";char* path = realpath(filename, NULL);if(path == NULL){    printf("cannot find file with name[%s]\n", filename);} else{    printf("path[%s]\n", path);    free(path);}

There is also a small path library cwalk which works cross-platform. It has cwk_path_get_absolute to do that:

#include <cwalk.h>#include <stdio.h>#include <stddef.h>#include <stdlib.h>int main(int argc, char *argv[]){  char buffer[FILENAME_MAX];  cwk_path_get_absolute("/hello/there", "./world", buffer, sizeof(buffer));  printf("The absolute path is: %s", buffer);  return EXIT_SUCCESS;}

Outputs:

The absolute path is: /hello/there/world