How do I check if all libraries are available?

Run 'ldd executable' and look for 'not found' messages. These indicate missing libraries that need to be installed or linked properly.

ldd Command

Q: What does the ldd command do in Linux?

The ldd command displays the shared library dependencies of an executable or shared library. It shows which libraries are needed and where they are located.

Q: Is ldd safe to use on untrusted executables?

No, never run ldd on untrusted executables as it may execute code from the target program during analysis. Use objdump or readelf instead for untrusted files.

The ldd command displays the shared library dependencies of an executable or shared library. It shows which dynamic libraries are required by a program and where they are located in the filesystem.

Syntax

ldd [OPTION]... FILE...

Description

The ldd command is essential for debugging library-related issues and understanding program dependencies. It shows which dynamic libraries are required and their memory addresses.

Common uses include:

Display shared library dependencies
Identify missing or broken library links
Debug dynamic linking issues
Analyze program dependencies for deployment

Security Warning: Never run ldd on untrusted executables as it may execute code from the target program during analysis.

Common Options

Option	Description
`-v`	Verbose mode - show version information
`-d`	Perform data relocations and report missing objects
`-r`	Perform data and function relocations
`-u`	Show unused direct dependencies
`--help`	Display help information
`--version`	Display version information

Examples

Display dependencies of an executable

ldd /bin/ls

Shows all shared libraries required by the ls command

Check dependencies of a custom program

ldd ./myprogram

Displays dependencies for a custom executable

Verbose output with version information

ldd -v /bin/echo

Shows detailed version information for each library

Check for missing libraries

ldd ./broken_program

Look for "not found" messages indicating missing libraries

Analyze shared library dependencies

ldd /usr/lib/x86_64-linux-gnu/libssl.so.1.1

Shows what libraries a shared library itself depends on

Check unused dependencies

ldd -u ./myprogram

Identifies libraries that are linked but not actually used

Understanding Output

The ldd output format shows:

Library name - The name of the shared library
Arrow (=>) - Points to the actual library location
Library path - Full path to the library file
Memory address - Virtual memory address where library is loaded

Special cases:

not found - Library is missing or not in library path
linux-vdso.so.1 - Virtual dynamic shared object (kernel interface)
/lib64/ld-linux-x86-64.so.2 - Dynamic linker/loader
statically linked - Executable has no dynamic dependencies