Getting absolute path of a file

How can I convert a relative path to an absolute path in C on Unix? Is there a convenient system function for this?

On Windows there is a GetFullPathName function that does the job, but I didn't find something similar on Unix...


  • 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);