1.\" Copyright (c) 2024 The FreeBSD Foundation 2.\" 3.\" This documentation was written by 4.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship 5.\" from the FreeBSD Foundation. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd October 31, 2024 29.Dt RTLD_GET_VAR 3 30.Os 31.Sh NAME 32.Nm rtld_get_var , 33.Nm rtld_set_var 34.Nd query or change run-time linker parameters after image activation 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In sys/errno.h 39.In link.h 40.Ft const char * 41.Fn rtld_get_var "const char *name" 42.Ft int 43.Fn rtld_set_var "const char *name" "const char *value" 44.Sh DESCRIPTION 45The dynamic linker 46.Xr rtld 1 47can be configured be setting some environment variables for the process, 48before image activation. 49Sometimes it is desirable to query the current effective settings or 50change them afterward. 51.Pp 52Since the process environment variables are maintained by higher-level 53libraries, the run-time linker cannot access them after the image 54activation. 55The described functions make it possible to operate on rtld settings. 56.Pp 57The 58.Fn rtld_get_var 59function returns the current value of the named parameter. 60.Pp 61The 62.Fn rtld_set_var 63functions changes the value of the parameter to the new 64.Fa value 65value, if possible. 66The 67.Fa name 68argument to both functions is the name of the parameter, which 69is same as the corresponding environment variable 70.Pq see Xr rtld 1 71but without the 72.Ev LD_ 73(or 74.Ev LD_32_ 75or any other ABI-specific) prefix. 76.Sh RETURN VALUES 77The 78.Fn rtld_get_var 79returns the current value of the named parameter, or 80.Dv NULL 81if the name is invalid. 82.Pp 83The 84.Fn rtld_set_var 85returns 0 on success, or an integer indicating the error condition 86which prevented the operation. 87.Sh ERRORS 88Possible errors returned from 89.Fn rtld_set_var : 90.Bl -tag -width Er 91.It Bq Er EPERM 92The requested change cannot be made at runtime, either because the 93runtime linker can only take this parameter at initialization time, 94or because the current process is executing with elevated privileges. 95.It Bq ENOENT 96The supplied parameter 97.Fa name 98is unknown. 99.El 100.Sh SEE ALSO 101.Xr rtld 1 102.Sh HISTORY 103The 104.Nm 105function first appeared in 106.Fx 15.0 . 107