basename, dirname - parse pathname components
Warning: there are two different functions basename() - see below.
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.
path does not contain a slash, dirname()
returns the string "." while basename() returns a copy
path is the string "/", then both
dirname() and basename() return the
string "/". If
path is a null pointer or points to an empty
string, then both dirname() and
basename() return the string ".".
These functions may return pointers to statically allocated memory
which may be overwritten by subsequent calls. Alternatively, they may
return a pointer to some part of
path, so that the string
referred to by
path should not be modified or freed until the
pointer returned by the function is no longer required.
path dirname basename /usr/lib /usr lib /usr/ / usr usr . usr / / / . . . .. . ..
There are two different versions of basename() - the POSIX version described above, and the GNU version, which one gets after
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <string.h>
The GNU version never modifies its argument, and returns the empty
path has a trailing slash, and in particular also
when it is "/". There is no GNU version of
With glibc, one gets the POSIX version of basename()
<libgen.h> is included, and the GNU version
In the glibc implementation, the POSIX versions of these functions
path argument, and segfault when called with a
static string such as "/usr/".
Before glibc 2.2.1, the glibc version of dirname() did not correctly handle pathnames with trailing '/' characters, and generated a segfault if given a NULL argument.
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