dirname() in C: is the manual wrong?
c, dirname
Solution
Trailing '/' characters are not counted as part of the pathname.
Hence "/usr/" is the same as "/usr", which might denote a file or a directory with name (directory entry named) `usr` in the directory `/`. The function `dirname` returns the parent directory of the path. The parent directory of `/usr` is `/`. Seems entirely consistent.
Problem
Citing the manual here: The functions dirname() and basename() break a null-terminated pathname string into directory and filename components. In the usual case, dirname() returns the string up to, but not including, the final '/', and basename() returns the component following the final '/'. Trailing '/' characters are not counted as part of the pathname. And later on, you have this little table: ``` path dirname basename "/usr/lib" "/usr" "lib" "/usr/" "/" "usr" // wat? "usr" "." "usr" "/" "/" "/" "." "." "." ".." "." ".." ``` Why is `dirname( "/usr/")` returning `"/"` and not `"/usr"` ? The sentence in the manual tells me I should get `/usr` as a result. I tested the actual result in a dummy program and it behaves just like the manual says. ``` #include <libgen.h> #include <stdio.h> #include <string.h> #include <stdlib.h> int main(int argc, char const *argv[]) { const char *mydir="/usr/"; char *dummy = strdup( mydir ); char *dummy2 = strdup( mydir ); char *dname = dirname( dummy ); char *bname = basename( dummy2 ); printf("mydir: '%s', dname: '%s', bname: '%s'\n", mydir, dname, bname); free( dummy ); free( dummy2 ); return 0; } $ ./test mydir: '/usr/', dname: '/', bname: 'usr' ``` Now, what I would expect would be: ``` path dirname basename "/usr/" "/usr" "" // more consistent? ``` So.. anybody understands what's going on here?