basename(3)

1basename(3)                Library Functions Manual                basename(3)
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NAME

6       basename, dirname - parse pathname components
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

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

18       Warning: there are two different functions basename(); see below.
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20       The functions dirname() and basename() break a null-terminated pathname
21       string into directory and filename  components.   In  the  usual  case,
22       dirname()  returns  the string up to, but not including, the final '/',
23       and basename() returns the component following the final '/'.  Trailing
24       '/' characters are not counted as part of the pathname.
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26       If  path  does  not  contain  a slash, dirname() returns the string "."
27       while basename() returns a copy of path.  If path is  the  string  "/",
28       then both dirname() and basename() return the string "/".  If path is a
29       null pointer or points to an empty  string,  then  both  dirname()  and
30       basename() return the string ".".
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32       Concatenating  the  string returned by dirname(), a "/", and the string
33       returned by basename() yields a complete pathname.
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35       Both dirname() and basename() may modify the contents of  path,  so  it
36       may be desirable to pass a copy when calling one of these functions.
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38       These  functions  may  return  pointers  to statically allocated memory
39       which may be overwritten by subsequent calls.  Alternatively, they  may
40       return  a  pointer to some part of path, so that the string referred to
41       by path should not be modified or freed until the pointer  returned  by
42       the function is no longer required.
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44       The following list of examples (taken from SUSv2) shows the strings re‐
45       turned by dirname() and basename() for different paths:
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47              path       dirname   basename
48              /usr/lib   /usr      lib
49              /usr/      /         usr
50              usr        .         usr
51              /          /         /
52              .          .         .
53              ..         .         ..
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RETURN VALUE

56       Both  dirname()  and  basename()  return  pointers  to  null-terminated
57       strings.  (Do not pass these pointers to free(3).)
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ATTRIBUTES

60       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
61       tributes(7).
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63       ┌────────────────────────────────────────────┬───────────────┬─────────┐
64       │Interface                                   │ Attribute     │ Value   │
65       ├────────────────────────────────────────────┼───────────────┼─────────┤
66       │basename(), dirname()                       │ Thread safety │ MT-Safe │
67       └────────────────────────────────────────────┴───────────────┴─────────┘
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VERSIONS

70       There are two different versions of basename() - the POSIX version  de‐
71       scribed above, and the GNU version, which one gets after
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73               #define _GNU_SOURCE         /* See feature_test_macros(7) */
74               #include <string.h>
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76       The  GNU  version  never  modifies  its argument, and returns the empty
77       string when path has a trailing slash, and in particular also  when  it
78       is "/".  There is no GNU version of dirname().
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80       With glibc, one gets the POSIX version of basename() when <libgen.h> is
81       included, and the GNU version otherwise.
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STANDARDS

84       POSIX.1-2008.
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HISTORY

87       POSIX.1-2001.
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BUGS

90       In the glibc implementation, the POSIX versions of these functions mod‐
91       ify  the  path  argument, and segfault when called with a static string
92       such as "/usr/".
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94       Before glibc 2.2.1, the glibc version of dirname()  did  not  correctly
95       handle pathnames with trailing '/' characters, and generated a segfault
96       if given a NULL argument.
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EXAMPLES

99       The following code snippet  demonstrates  the  use  of  basename()  and
100       dirname():
101           char *dirc, *basec, *bname, *dname;
102           char *path = "/etc/passwd";
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104           dirc = strdup(path);
105           basec = strdup(path);
106           dname = dirname(dirc);
107           bname = basename(basec);
108           printf("dirname=%s, basename=%s\n", dname, bname);
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