.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992

.\"

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.\" Modified by Michael Haardt <michael@moria.de>

.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>

.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>

.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>

.\" Modified 2005-01-09 by aeb

.\"

.TH USELIB 2 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

uselib \- load shared library

.SH SYNOPSIS

.B #include <unistd.h>

.PP

.BI "int uselib(const char *" library );

.PP

.IR Note :

No declaration of this system call is provided in glibc headers; see NOTES.

.SH DESCRIPTION

The system call

.BR 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.

.SH RETURN VALUE

On success, zero is returned.

On error, \-1 is returned, and

.I errno

is set appropriately.

.SH ERRORS

In addition to all of the error codes returned by

.BR open (2)

and

.BR mmap (2),

the following may also be returned:

.TP

.B EACCES

The library specified by

.I 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

.BR path_resolution (7).)

.TP

.B ENFILE

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

.TP

.B ENOEXEC

The file specified by

.I library

is not an executable of a known type;

for example, it does not have the correct magic numbers.

.SH CONFORMING TO

.BR uselib ()

is Linux-specific, and should not be used in programs

intended to be portable.

.SH NOTES

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

.BR syscall (2).

.PP

In ancient libc versions,

.BR uselib ()

was used to load

the shared libraries with names found in an array of names

in the binary.

.PP

.\" libc 4.3.1f - changelog 1993-03-02

Since libc 4.3.2, startup code tries to prefix these names

with "/usr/lib", "/lib" and "" before giving up.

.\" libc 4.3.4 - changelog 1993-04-21

In libc 4.3.4 and later these names are looked for in the directories

found in

.BR LD_LIBRARY_PATH ,

and if not found there,

prefixes "/usr/lib", "/lib" and "/" are tried.

.PP

From libc 4.4.4 on only the library "/lib/ld.so" is loaded,

so that this dynamic library can load the remaining libraries needed

(again using this call).

This is also the state of affairs in libc5.

.PP

glibc2 does not use this call.

.PP

Since Linux 3.15,

.\" commit 69369a7003735d0d8ef22097e27a55a8bad9557a

this system call is available only when the kernel is configured with the

.B CONFIG_USELIB

option.

.SH SEE ALSO

.BR ar (1),

.BR gcc (1),

.BR ld (1),

.BR ldd (1),

.BR mmap (2),

.BR open (2),

.BR dlopen (3),

.BR capabilities (7),

.BR ld.so (8)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.