telldir - return current location in directory stream
#include <dirent.h>
long telldir(DIR *dirp);Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
telldir(): _XOPEN_SOURCE || /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The telldir() function returns the current location
associated with the directory stream dirp.
On success, the telldir() function returns the
current location in the directory stream. On error, -1 is returned, and
errno is set appropriately.
Invalid directory stream descriptor dirp.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| telldir() | Thread safety | MT-Safe |
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
In glibc up to version 2.1.1, the return type of
telldir() was off_t. POSIX.1-2001 specifies
long, and this is the type used since glibc 2.1.2.
In early filesystems, the value returned by
telldir() was a simple file offset within a directory.
Modern filesystems use tree or hash structures, rather than flat tables,
to represent directories. On such filesystems, the value returned by
telldir() (and used internally by
readdir(3)) is a "cookie" that is used by the
implementation to derive a position within a directory. Application
programs should treat this strictly as an opaque value, making
no assumptions about its contents.
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