USELIB(2) Linux Programmer's Manual USELIB(2)
uselib - load shared library
int uselib(const char *library);
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 appropriately.
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 pre-
fix. (See also path_resolution(7).)
ENFILE The system limit on the total number of open files has been reached.
The file specified by library is not an executable of known type, e.g., does not
have the correct magic numbers.
uselib() is Linux-specific, and should not be used in programs intended to be portable.
uselib() was used by early libc startup code 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
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.
ar(1), gcc(1), ld(1), ldd(1), mmap(2), open(2), dlopen(3), capabilities(7), ld.so(8)
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Linux 2005-01-09 USELIB(2)