rtld_get_var(3)

NAME

rtld_get_var, rtld_set_var – query or change run-time linker parameters after image activation

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <sys/errno.h>

#include <link.h>

const char *

rtld_get_var(const char *name);

int

rtld_set_var(const char *name, const char *value);

DESCRIPTION

The dynamic linker rtld(1) can be configured by setting some environment variables for the process, before image activation. Sometimes it is desirable to query the current effective settings or change them afterward.

Since the process environment variables are maintained by higher-level libraries, the run-time linker cannot access them after the image activation. The described functions make it possible to operate on rtld settings.

The rtld_get_var() function returns the current value of the named parameter.

The rtld_set_var() functions changes the value of the parameter to the new value value, if possible. The name argument to both functions is the name of the parameter, which is same as the corresponding environment variable (see rtld(1)) but without the LD_ (or LD_32_ or any other ABI-specific) prefix.

The list of variables that can be modified with the rtld_set_var() function is:

LD_BIND_NOT
LD_BIND_NOW
LD_DEBUG
LD_DUMP_REL_PRE
LD_DUMP_REL_POST
LD_DYNAMIC_WEAK
LD_LIBMAP_DISABLE
LD_LIBRARY_PATH
LD_LIBRARY_PATH_FDS
LD_LIBRARY_PATH_RPATH
LD_LOADFLTR

RETURN VALUES

The rtld_get_var() returns the current value of the named parameter, or NULL if the name is invalid.

The rtld_set_var() returns 0 on success, or an integer indicating the error condition which prevented the operation.

ERRORS

Possible errors returned from rtld_set_var():

[EPERM]: The requested change cannot be made at runtime, either because the runtime linker can only take this parameter at initialization time, or because the current process is executing with elevated privileges.
[ENOENT]: The supplied parameter name is unknown.

HISTORY

The rtld_get_var function first appeared in FreeBSD 14.3.