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man:uselib

USELIB(2) Linux Programmer's Manual USELIB(2)

NAME

     uselib - load shared library

SYNOPSIS

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

DESCRIPTION

     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  recog-
     nized binary format.

RETURN VALUE

     On  success,  zero is returned.  On error, -1 is returned, and errno is
     set appropriately.

ERRORS

     In addition to all of the error codes returned by open(2) and  mmap(2),
     the following may also be returned:
     EACCES 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_reso-
            lution(7).)
     ENFILE The system-wide limit on the total number of open files has been
            reached.
     ENOEXEC
            The  file  specified  by library is not an executable of a known
            type; for example, it does not have the correct magic numbers.

CONFORMING TO

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

NOTES

     This obsolete system call is not supported by glibc.  No declaration is
     provided in glibc headers, but, through a quirk of history, glibc  ver-
     sions  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,  uselib()  was  used  to  load  the  shared
     libraries with names found in an array of names in the binary.
     Since  libc  4.3.2,  startup  code  tries  to  prefix  these names with
     "/usr/lib", "/lib" and "" before giving up.  In libc  4.3.4  and  later
     these names are looked for in the directories found in LD_LIBRARY_PATH,
     and if not found there, prefixes "/usr/lib", "/lib" and "/" are  tried.
     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.
     glibc2 does not use this call.
     Since Linux 3.15, this system call is available only when the kernel is
     configured with the CONFIG_USELIB option.

SEE ALSO

     ar(1), gcc(1), ld(1), ldd(1), mmap(2),  open(2),  dlopen(3),  capabili-
     ties(7), ld.so(8)

COLOPHON

     This  page  is  part of release 4.16 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
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 USELIB(2)

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