The Libdl module in Julia provides specialized and lower-level facilities for dynamic linking with shared libraries. While Julia inherently supports linking to runtime shared libraries through theccall intrinsic,Libdl extends this capability by offering additional, more granular control. It enables users to search for shared libraries both in memory and the filesystem, manually load them with specific runtime linker options, and look up library symbols as low-level pointers.

dlopen(libfile::AbstractString [, flags::Integer]; throw_error:Bool = true)

Load a shared library, returning an opaque handle.

The extension given by the constantdlext (.so,.dll, or.dylib) can be omitted from thelibfile string, as it is automatically appended if needed. Iflibfile is not an absolute path name, then the paths in the arrayDL_LOAD_PATH are searched forlibfile, followed by the system load path.

The optional flags argument is a bitwise-or of zero or more ofRTLD_LOCAL,RTLD_GLOBAL,RTLD_LAZY,RTLD_NOW,RTLD_NODELETE,RTLD_NOLOAD,RTLD_DEEPBIND, andRTLD_FIRST. These are converted to the corresponding flags of the POSIX (and/or GNU libc and/or MacOS) dlopen command, if possible, or are ignored if the specified functionality is not available on the current platform. The default flags are platform specific. On MacOS the defaultdlopen flags areRTLD_LAZY|RTLD_DEEPBIND|RTLD_GLOBAL while on other platforms the defaults areRTLD_LAZY|RTLD_DEEPBIND|RTLD_LOCAL. An important usage of these flags is to specify non default behavior for when the dynamic library loader binds library references to exported symbols and if the bound references are put into process local or global scope. For instanceRTLD_LAZY|RTLD_DEEPBIND|RTLD_GLOBAL allows the library's symbols to be available for usage in other shared libraries, addressing situations where there are dependencies between shared libraries.

If the library cannot be found, this method throws an error, unless the keyword argumentthrow_error is set tofalse, in which case this method returnsnothing.

dlopen_e(libfile::AbstractString [, flags::Integer])

Similar todlopen, except returnsC_NULL instead of raising errors. This method is now deprecated in favor ofdlopen(libfile::AbstractString [, flags::Integer]; throw_error=false).

RTLD_DEEPBINDRTLD_FIRSTRTLD_GLOBALRTLD_LAZYRTLD_LOCALRTLD_NODELETERTLD_NOLOADRTLD_NOW

Enum constant fordlopen. See your platform man page for details, if applicable.

dlsym(handle, sym; throw_error::Bool = true)

Look up a symbol from a shared library handle, return callable function pointer on success.

If the symbol cannot be found, this method throws an error, unless the keyword argumentthrow_error is set tofalse, in which case this method returnsnothing.

dlsym_e(handle, sym)

Look up a symbol from a shared library handle, silently returnC_NULL on lookup failure. This method is now deprecated in favor ofdlsym(handle, sym; throw_error=false).

dlclose(::Nothing)

For the very common pattern usage pattern of

try    hdl = dlopen(library_name)    ... do somethingfinally    dlclose(hdl)end

We define adlclose() method that accepts a parameter of typeNothing, so that user code does not have to change its behavior for the case thatlibrary_name was not found.

dlclose(handle)

Close shared library referenced by handle.

dlext

File extension for dynamic libraries (e.g. dll, dylib, so) on the current platform.

dllist()

Return the paths of dynamic libraries currently loaded in aVector{String}.

dlpath(libname::Union{AbstractString, Symbol})

Get the full path of the librarylibname.

Examples

julia> dlpath("libjulia")

dlpath(handle::Ptr{Cvoid})

Given a libraryhandle fromdlopen, return the full path.

find_library(names [, locations])

Searches for the first library innames in the paths in thelocations list,DL_LOAD_PATH, or system library paths (in that order) which can successfully be dlopen'd. On success, the return value will be one of the names (potentially prefixed by one of the paths in locations). This string can be assigned to aglobal const and used as the library name in futureccall's. On failure, it returns the empty string.

DL_LOAD_PATH

When callingdlopen, the paths in this list will be searched first, in order, before searching the system locations for a valid library handle.