This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
The dlerror() function shall return a null-terminated character
string (with no trailing <newline>) that describes the last error
that occurred during dynamic linking processing. If no dynamic
linking errors have occurred since the last invocation of dlerror(),
dlerror() shall return NULL. Thus, invoking dlerror() a second time,
immediately following a prior invocation, shall result in NULL being
It is implementation-defined whether or not the dlerror() function is
thread-safe. A thread-safe implementation shall return only errors
that occur on the current thread.
If successful, dlerror() shall return a null-terminated character
string; otherwise, NULL shall be returned.
The application shall not modify the string returned. The returned
pointer might be invalidated or the string content might be
overwritten by a subsequent call to dlerror() in the same thread (if
dlerror() is thread-safe) or in any thread (if dlerror() is not
The following example prints out the last dynamic linking error:
errstr = dlerror();
if (errstr != NULL)
printf ("A dynamic linking error occurred: (%s)\n", errstr);
Depending on the application environment with respect to asynchronous
execution events, such as signals or other asynchronous computation
sharing the address space, conforming applications should use a
critical section to retrieve the error pointer and buffer.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 DLERROR(3P)