'\" t .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .\" References consulted: .\" Linux libc source code .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) .\" 386BSD man pages .\" Modified Sat Jul 24 17:48:42 1993 by Rik Faith (faith@cs.unc.edu) .TH telldir 3 2023-03-30 "Linux man-pages 6.04" .SH NAME telldir \- return current location in directory stream .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .PP .BI "long telldir(DIR *" dirp ); .fi .PP .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .PP .BR telldir (): .nf _XOPEN_SOURCE || /* glibc >= 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION The .BR telldir () function returns the current location associated with the directory stream \fIdirp\fP. .SH RETURN VALUE On success, the .BR telldir () function returns the current location in the directory stream. On error, \-1 is returned, and .I errno is set to indicate the error. .SH ERRORS .TP .B EBADF Invalid directory stream descriptor \fIdirp\fP. .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 telldir () T} Thread safety MT-Safe .TE .hy .ad .sp 1 .SH STANDARDS POSIX.1-2008. .SH HISTORY POSIX.1-2001, 4.3BSD. .PP Up to glibc 2.1.1, the return type of .BR telldir () was .IR off_t . POSIX.1-2001 specifies .IR long , and this is the type used since glibc 2.1.2. .PP In early filesystems, the value returned by .BR 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 .BR telldir () (and used internally by .BR readdir (3)) is a "cookie" that is used by the implementation to derive a position within a directory. .\" https://lwn.net/Articles/544298/ Application programs should treat this strictly as an opaque value, making .I no assumptions about its contents. .SH SEE ALSO .BR closedir (3), .BR opendir (3), .BR readdir (3), .BR rewinddir (3), .BR scandir (3), .BR seekdir (3)