1 .\" $FreeBSD: src/libexec/rtld-elf/rtld.1,v 1.18.2.7 2002/01/10 17:51:28 ru Exp $
2 .\" $DragonFly: src/libexec/rtld-elf/rtld.1,v 1.2 2003/06/17 04:27:08 dillon Exp $
4 .\" Copyright (c) 1995 Paul Kranenburg
5 .\" All rights reserved.
7 .\" Redistribution and use in source and binary forms, with or without
8 .\" modification, are permitted provided that the following conditions
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11 .\" notice, this list of conditions and the following disclaimer.
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14 .\" documentation and/or other materials provided with the distribution.
15 .\" 3. All advertising materials mentioning features or use of this software
16 .\" must display the following acknowledgment:
17 .\" This product includes software developed by Paul Kranenburg.
18 .\" 3. The name of the author may not be used to endorse or promote products
19 .\" derived from this software without specific prior written permission
21 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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38 .Nd run-time link-editor
41 is a self-contained shared object providing run-time
42 support for loading and link-editing shared objects into a process'
44 It is also commonly known as the dynamic linker.
45 It uses the data structures
46 contained within dynamically linked programs to determine which shared
47 libraries are needed and loads them using the
51 After all shared libraries have been successfully loaded,
53 proceeds to resolve external references from both the main program and
55 A mechanism is provided for initialization routines
56 to be called on a per-object basis, giving a shared object an opportunity
57 to perform any extra set-up before execution of the program proper begins.
58 This is useful for C++ libraries that contain static constructors.
61 itself is loaded by the kernel together with any dynamically-linked
62 program that is to be executed.
63 The kernel transfers control to the
65 After the dynamic linker has finished loading,
66 relocating, and initializing the program and its required shared
67 objects, it transfers control to the entry point of the program.
69 To locate the required shared objects in the filesystem,
78 recognizes a number of environment variables that can be used to modify
79 its behaviour as follows:
81 .Bl -tag -width ".Ev LD_LIBRARY_PATH"
82 .It Ev LD_LIBRARY_PATH
83 A colon separated list of directories, overriding the default search path
85 This is ignored for set-user-ID and set-group-ID programs.
87 A list of shared libraries, separated by colons and/or white space,
88 to be linked in before any
89 other shared libraries.
90 If the directory is not specified then
91 the directories specified by
93 will be searched first
94 followed by the set of built-in standard directories.
95 This is ignored for set-user-ID and set-group-ID programs.
97 When set to a nonempty string, causes
99 to relocate all external function calls before starting execution of the
101 Normally, function calls are bound lazily, at the first call
104 increases the start-up time of a program, but it avoids run-time
105 surprises caused by unexpectedly undefined functions.
106 .It Ev LD_TRACE_LOADED_OBJECTS
107 When set to a nonempty string, causes
109 to exit after loading the shared objects and printing a summary which includes
110 the absolute pathnames of all objects, to standard output.
111 .It Ev LD_TRACE_LOADED_OBJECTS_FMT1
112 .It Ev LD_TRACE_LOADED_OBJECTS_FMT2
113 When set, these variables are interpreted as format strings a la
115 to customize the trace output and are used by
120 to be operated as a filter more conveniently.
121 The following conversions can be used:
124 The main program's name
128 The value of the environment variable
129 .Ev LD_TRACE_LOADED_OBJECTS_PROGNAME
133 The library's major version number.
135 The full pathname as determined by
137 library search rules.
139 The library's load address.
146 are recognized and have their usual meaning.
149 .Bl -tag -width indent
150 .It Pa /var/run/ld-elf.so.hints