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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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ld

ld [options] objfiles

Combine several objfiles, in the specified order, into a single executable object module (a.out by default). ld is the link editor and is often invoked automatically by compiler commands. ld accepts many options, the most common of which are listed here.

Options

-b format, --format=format

If ld is configured to accept more than one kind of object file, this option can be used to specify the input format. format should be a GNU Binary File Descriptor (BFD), as described in the BFD library. Use objdump -i to list available formats.

-call_shared

Link with dynamic libraries.

-d, -dc, -dp

Force the assignment of space to common symbols.

-defsym symbol=expression

Create the global symbol with the value expression.

-demangle[=style]

Force demangling of symbol names. Optionally set the demangling style. Turn off demangling with -nodemangle.

-e symbol

Set symbol as the address of the output file's entry point.

-f name

Set the DT_AUXILIARY field of ELF shared object to name.

-fini name

Set the DT_FINI field of ELF shared object to the address of function name. The default function is _fini.

-h name

Set the DT_SONAME field of ELF shared object to name.

--help

Print help message, then exit.

-i

Produce a linkable output file; attempt to set its magic number to OMAGIC.

-init name

Set the DT_INIT field of ELF shared object to the address of function name. The default function is _init.

-larch, --library=archive

Include the archive file arch in the list of files to link.

-m linker

Emulate linker. List supported emulations with the -V option.

-n

Make text read-only; attempt to set NMAGIC.

-o output

Place output in output, instead of in a.out.

-oformat format

Specify output format.

-q

Retain relocation sections and contents in linked executables.

-r

Produce a linkable output file; attempt to set its magic number to OMAGIC.

-rpath dir

Add directory dir to the runtime library search path. Ignore additional paths normally read from the LD_RUN_PATH environment variable.

-rpath-link dirs

Specify path to search for shared libraries required by another shared library. The dirs argument can be a single directory, or multiple directories separated by colons. This overrides search paths specified in shared libraries themselves.

-s

Do not include any symbol information in output.

-shared

Create a shared library.

-static

Do not link with shared libraries.

-sort-common

Do not sort global common symbols by size.

-t

Print each input file's name as it is processed.

--target-help

Print target-specific options, then exit.

-u symbol

Force symbol to be undefined.

-v, --version

Show version number.

--verbose

Print information about ld; print the names of input files while attempting to open them.

-warn-common

Warn when encountering common symbols combined with other constructs.

-warn-once

Provide only one warning per undefined symbol.

-x

With -s or -S, delete all local symbols. These generally begin with L.

-z keyword

Mark the object for special behavior specified by keyword. ld recognizes the following keywords:

combreloc

Object combines and sorts multiple relocation sections for dynamic symbol lookup caching.

defs

Disallow undefined symbols.

initfirst

Initialize object first at runtime.

interpose

Interpose object's symbol table before all but the primary executable's symbol table.

loadfltr

Process object's filter immediately at runtime.

multidefs

Allow multiple definitions of a single symbol. Use the first definition.

nocombreloc

Disable combining multiple relocation sections.

nocopyreloc

Disable copy relocation.

nodefaultlib

Ignore default library search path when seeking dependencies for object.

nodelete

Do not unload object at runtime.

nodlopen

Object is not available to dlopen.

nodump

Object cannot be dumped by dldump.

now

Non-lazy runtime binding.

origin

Object may contain $ORIGIN.

-E, --export-dynamic

Add all symbols to dynamic symbol table, not just those referenced by linked objects.

-EB

Link big-endian objects.

-EL

Link little-endian objects.

-F name

Set DT_FILTER field of ELF shared object to name.

-Ldir, --library-path=dir

Search directory dir before standard search directories (this option must precede the -l option that searches that directory).

-M

Display a link map on standard output.

-Map file

Print a link map to file.

-N

Allow reading of and writing to both data and text. Mark ouput if it supports Unix magic numbers. Do not page-align data.

-O level

Optimize. level should be 1, 2, 3, or 0. The default is 1. 0 turns off optimization; 3 optimizes the most.

-R file

Obtain symbol names and addresses from file, but suppress relocation of file and its inclusion in output.

-S

Do not include debugger symbol information in output.

-T file

Execute script file instead of the default linker script.

-Tbss address

Begin bss segment of output at address.

-Tdata address

Begin data segment of output at address.

-Ttext address

Begin text segment of output at address.

-Ur

Synonymous with -r except when linking C++ programs, where it resolves constructor references.

-X

With -s or -S, delete local symbols beginning with L.

-V

Show version number and emulation linkers for -m option.


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