dirname(3)

1DIRNAME(3)                 Linux Programmer's Manual                DIRNAME(3)
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NAME

6       dirname, basename - parse pathname components
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SYNOPSIS

9       #include <libgen.h>
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11       char *dirname(char *path);
12       char *basename(char *path);
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DESCRIPTION

15       Warning: there are two different functions basename() - see below.
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17       The functions dirname() and basename() break a null-terminated pathname
18       string into directory and filename  components.   In  the  usual  case,
19       dirname()  returns  the string up to, but not including, the final '/',
20       and basename() returns the component following the final '/'.  Trailing
21       '/' characters are not counted as part of the pathname.
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23       If  path  does  not  contain  a slash, dirname() returns the string "."
24       while basename() returns a copy of path.  If path is  the  string  "/",
25       then both dirname() and basename() return the string "/".  If path is a
26       NULL pointer or points to an empty  string,  then  both  dirname()  and
27       basename() return the string ".".
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29       Concatenating  the  string returned by dirname(), a "/", and the string
30       returned by basename() yields a complete pathname.
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32       Both dirname() and basename() may modify the contents of  path,  so  it
33       may be desirable to pass a copy when calling one of these functions.
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35       These  functions  may  return  pointers  to statically allocated memory
36       which may be overwritten by subsequent calls.  Alternatively, they  may
37       return  a  pointer to some part of path, so that the string referred to
38       by path should not be modified or freed until the pointer  returned  by
39       the function is no longer required.
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41       The  following  list  of  examples (taken from SUSv2) shows the strings
42       returned by dirname() and basename() for different paths:
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44       path           dirname        basename
45       "/usr/lib"     "/usr"         "lib"
46       "/usr/"        "/"            "usr"
47       "usr"          "."            "usr"
48       "/"            "/"            "/"
49       "."            "."            "."
50       ".."           "."            ".."
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EXAMPLE

53              char *dirc, *basec, *bname, *dname;
54              char *path = "/etc/passwd";
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56              dirc = strdup(path);
57              basec = strdup(path);
58              dname = dirname(dirc);
59              bname = basename(basec);
60              printf("dirname=%s, basename=%s\n", dname, bname);
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RETURN VALUE

63       Both  dirname()  and  basename()  return  pointers  to  null-terminated
64       strings.
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NOTES

67       There  are  two  different  versions  of basename() - the POSIX version
68       described above, and the GNU version, which one gets after
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70           #define _GNU_SOURCE
71           #include <string.h>
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73       The GNU version never modifies its  argument,  and  returns  the  empty
74       string  when  path has a trailing slash, and in particular also when it
75       is "/".  There is no GNU version of dirname().
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77       With glibc, one gets the POSIX version of basename() when <libgen.h> is
78       included, and the GNU version otherwise.
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BUGS

81       In  the  glibc  implementation of the POSIX versions of these functions
82       they modify their argument, and segfault  when  called  with  a  static
83       string  like  "/usr/".   Before  glibc  2.2.1,  the  glibc  version  of
84       dirname() did not correctly handle pathnames with trailing '/'  charac‐
85       ters, and generated a segfault if given a NULL argument.
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CONFORMING TO

88       POSIX.1-2001
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