uselib — load shared library


#include <unistd.h>
int uselib( const char *library);
[Note] Note
No declaration of this system call is provided in glibc headers; see NOTES.


The system call uselib() serves to load a shared library to be used by the calling process. It is given a pathname. The address where to load is found in the library itself. The library can have any recognized binary format.


On success, zero is returned. On error, −1 is returned, and errno is set to indicate the error.


In addition to all of the error codes returned by open(2) and mmap(2), the following may also be returned:


The library specified by library does not have read or execute permission, or the caller does not have search permission for one of the directories in the path prefix. (See also path_resolution(7).)


The system-wide limit on the total number of open files has been reached.


The file specified by library is not an executable of a known type; for example, it does not have the correct magic numbers.


uselib() is Linux-specific, and should not be used in programs intended to be portable.


This obsolete system call is not supported by glibc. No declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an ABI for this system call. Therefore, in order to employ this system call, it was sufficient to manually declare the interface in your code; alternatively, you could invoke the system call using syscall(2).

In ancient libc versions (before glibc 2.0), uselib() was used to load the shared libraries with names found in an array of names in the binary.

Since Linux 3.15, this system call is available only when the kernel is configured with the CONFIG_USELIB option.


ar(1), gcc(1), ld(1), ldd(1), mmap(2), open(2), dlopen(3), capabilities(7),


This page is part of release 5.11 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at−pages/.

  Copyright (c) 1992 Drew Eckhardt (, March 28, 1992

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

Modified by Michael Haardt <>
Modified 1993-07-24 by Rik Faith <>
Modified 1996-10-22 by Eric S. Raymond <>
Modified 2004-06-23 by Michael Kerrisk <>
Modified 2005-01-09 by aeb