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basename(3) Library Functions Manual basename(3) NAME basename, dirname, dirname_r - Return the base filename or directory portion of a pathname LIBRARY Standard C Library (libc.so, libc.a) SYNOPSIS #include <libgen.h> char *basename( char *path); char *dirname( char *path); The following function is supported only for backward compatibility: #include <string.h> int dirname_r( char *path, char *buf, int size); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: basename(), dirname(): XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS The string from which the base pathname or the directory portion is to be extracted. [Digital] Specifies a working buffer to hold the direc- tory name component. [Digital] Specifies the length of buf. DESCRIPTION The basename() and dirname() functions complement each other. The basename() function reads path and returns a pointer to the final com- ponent of the pathname, deleting any trailing / (slash) characters. If the string consists entirely of the / (slash) character, basename() re- turns a pointer to the string / (slash). If path is a null pointer or points to an empty string, basename() returns a pointer to the string . (period). [Digital] In applications that are compiled in an environment that ex- cludes the _XOPEN_SOURCE_EXTENDED standard definitions, the basename() function returns an empty string if the string consists entirely of the / (slash) character. If path is a null pointer, basename() returns a core dump. If path points to an empty string, basename() returns an empty string. The dirname() function reads path and returns a pointer to a new string that is a pathname of the parent directory of that file. Trailing / (slash) characters in the path are not counted as part of the path. If there is no / (slash), if path is a null pointer, or if path points to an empty string, the dirname() function returns a pointer to the string . (period). [Digital] In applications that are compiled in an environment that ex- cludes the _XOPEN_SOURCE_EXTENDED standard definitions, the dirname() function returns a NULL if there is no / (slash), and a core dump if path is a null pointer, or if path points to an empty string. The dirname_r() function is the reentrant version of the dirname() function. It is supported to maintain backward compatibility with ver- sions of the operating system prior to Digital UNIX Version 4.0. NOTES The value returned by the basename() and dirname() functions is a pointer to a thread-specific buffer whose contents will be overwritten on subsequent calls from the same thread. [Digital] The basename(), dirname(), and dirname_r() functions belong to a small set of libc functions that are handled differently when com- piled in the X/Open UNIX environment. In the X/Open UNIX environment, calls to these functions are internally renamed by prepending _E to the function name. The renaming is done only when there is an incompatible conflict between an existing version of the function and the version that conforms to the X/Open UNIX standard. The renaming strategy sup- ports binary compatibility by allowing applications to compile in the X/Open UNIX environment and also link with site-specific and third- party libraries that use the old versions of the same libc interfaces. However, internal renaming of the calls affects how these calls are identified during debugging sessions. Therefore, when you are debug- ging a module that includes the basename() and/or dirname() or dirname_r() functions and for which _XOPEN_SOURCE_EXTENDED has been de- fined, use _Ebasename to refer to the basename() call and _Edirname to refer to the dirname call and _Edirname_r to refer to the dirname_r call. See standards(5) for information on when the _XOPEN_SOURCE_EX- TENDED macro is defined. RETURN VALUES Upon success, the basename() and dirname() functions return the compo- nent string. Upon failure, these functions return NULL. If there is no / (slash), the dirname() function returns a . (period). [Digital] In applications that are compiled in an environment that ex- cludes the _XOPEN_SOURCE_EXTENDED standard definitions, the dirname() function returns NULL if there is no / (slash). [Digital] Upon successful completion, the dirname_r() function returns a value of 0 (zero) and places the directory name component in the buffer pointed at by buf. Upon failure (for example, if there is no / (slash)), the dirname_r() function returns -1 and sets errno. ERRORS If the dirname_r() function fails, errno may be set to the following: The value of the buf parameter is invalid or too small. RELATED INFORMATION Commands: basename(1) Standards: standards(5) delim off basename(3)