| .\" Copyright (c) 2000 by Michael Kerrisk <mtk.manpages@gmail.com> |
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| .\" Created, 14 Dec 2000 by Michael Kerrisk |
| .\" |
| .TH BASENAME 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| basename, dirname \- parse pathname components |
| .SH SYNOPSIS |
| .nf |
| .B #include <libgen.h> |
| .PP |
| .BI "char *dirname(char *" path ); |
| .BI "char *basename(char *" path ); |
| .fi |
| .SH DESCRIPTION |
| Warning: there are two different functions |
| .BR basename () |
| - see below. |
| .PP |
| The functions |
| .BR dirname () |
| and |
| .BR basename () |
| break a null-terminated pathname string into directory |
| and filename components. |
| In the usual case, |
| .BR dirname () |
| returns the string up to, but not including, the final \(aq/\(aq, and |
| .BR basename () |
| returns the component following the final \(aq/\(aq. |
| Trailing \(aq/\(aq characters are not counted as part of the pathname. |
| .PP |
| If |
| .I path |
| does not contain a slash, |
| .BR dirname () |
| returns the string "." while |
| .BR basename () |
| returns a copy of |
| .IR path . |
| If |
| .I path |
| is the string "/", then both |
| .BR dirname () |
| and |
| .BR basename () |
| return the string "/". |
| If |
| .I path |
| is a null pointer or points to an empty string, then both |
| .BR dirname () |
| and |
| .BR basename () |
| return the string ".". |
| .PP |
| Concatenating the string returned by |
| .BR dirname (), |
| a "/", and the string returned by |
| .BR basename () |
| yields a complete pathname. |
| .PP |
| Both |
| .BR dirname () |
| and |
| .BR basename () |
| may modify the contents of |
| .IR path , |
| so it may be desirable to pass a copy when calling one of |
| these functions. |
| .PP |
| 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 |
| .IR path , |
| so that the string referred to by |
| .I path |
| should not be modified or freed until the pointer returned by |
| the function is no longer required. |
| .PP |
| The following list of examples (taken from SUSv2) |
| shows the strings returned by |
| .BR dirname () |
| and |
| .BR basename () |
| for different paths: |
| .RS |
| .TS |
| lb lb lb |
| l l l l. |
| path dirname basename |
| /usr/lib /usr lib |
| /usr/ / usr |
| usr . usr |
| / / / |
| \&. . . |
| \&.. . .. |
| .TE |
| .RE |
| .SH RETURN VALUE |
| Both |
| .BR dirname () |
| and |
| .BR basename () |
| return pointers to null-terminated strings. |
| (Do not pass these pointers to |
| .BR free (3).) |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR basename (), |
| .BR dirname () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| There are two different versions of |
| .BR basename () |
| - the POSIX version described above, and the GNU version, which one gets |
| after |
| .PP |
| .in +4n |
| .EX |
| .BR " #define _GNU_SOURCE" " /* See feature_test_macros(7) */" |
| .B " #include <string.h>" |
| .EE |
| .in |
| .PP |
| The GNU version never modifies its argument, and returns the |
| empty string when |
| .I path |
| has a trailing slash, and in particular also when it is "/". |
| There is no GNU version of |
| .BR dirname (). |
| .PP |
| With glibc, one gets the POSIX version of |
| .BR basename () |
| when |
| .I <libgen.h> |
| is included, and the GNU version otherwise. |
| .SH BUGS |
| In the glibc implementation, |
| the POSIX versions of these functions modify the |
| .I path |
| argument, and segfault when called with a static string |
| such as "/usr/". |
| .PP |
| Before glibc 2.2.1, the glibc version of |
| .BR dirname () |
| did not correctly handle pathnames with trailing \(aq/\(aq characters, |
| and generated a segfault if given a NULL argument. |
| .SH EXAMPLES |
| The following code snippet demonstrates the use of |
| .BR basename () |
| and |
| .BR dirname (): |
| .in +4n |
| .EX |
| char *dirc, *basec, *bname, *dname; |
| char *path = "/etc/passwd"; |
| |
| dirc = strdup(path); |
| basec = strdup(path); |
| dname = dirname(dirc); |
| bname = basename(basec); |
| printf("dirname=%s, basename=%s\en", dname, bname); |
| .EE |
| .in |
| .SH SEE ALSO |
| .BR basename (1), |
| .BR dirname (1) |