[SOLVED] How to Find Which Shared Library Contains a Specific Function in Shell Script?

Issue

I'm working on a shell script that needs to identify which shared library (.so file) contains a particular function. The script should be able to search within standard library directories such as /usr/lib, as well as in custom directories that are added to the LD_LIBRARY_PATH environment variable.

Is there a tool or a combination of tools that can help me achieve this? Ideally, I would like a solution that can be implemented in a shell script without the need for compiling additional programs. Any guidance or examples would be greatly appreciated!

Here is what I am aiming to achieve:

1. The script should take a function name as input.
2. It should then locate any shared library files that contain this function.
3. It should work with both standard system paths and paths included in LD_LIBRARY_PATH.

Solution

I've composed a shell script that should help you achieve your goal of finding which shared library contains a specific function. This script takes advantage of the nm command to list symbols from libraries and searches through the directories specified in your LD_LIBRARY_PATH as well as the standard library paths.

Here's the script:

#!/bin/bash

# Check if the function name was provided
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 <function_name>"
    exit 1
fi

function_name=$1

# Start with known common library paths
library_paths=("/lib" "/usr/lib" "/lib64" "/usr/lib64" "/usr/local/lib" "/usr/local/lib64" ".")

# Include paths from ld.so.conf
if [ -f "/etc/ld.so.conf" ]; then
    # Read the contents of ld.so.conf and include files from ld.so.conf.d
    ld_so_paths=$(cat /etc/ld.so.conf; find /etc/ld.so.conf.d/ -type f -exec cat {} +)
    for path in $ld_so_paths; do
        if [[ "$path" =~ ^/.* ]]; then
            library_paths+=("$path")
        fi
    done
fi

# Include paths from LD_LIBRARY_PATH if it is set
if [ -n "$LD_LIBRARY_PATH" ]; then
    IFS=':' read -ra ld_library_paths <<< "$LD_LIBRARY_PATH"
    library_paths+=("${ld_library_paths[@]}")
fi

# Remove duplicate paths
library_paths=($(printf "%s\n" "${library_paths[@]}" | sort -u))

# Check if nm is available
if ! command -v nm > /dev/null; then
    echo "Error: 'nm' command not found. Please install binutils."
    exit 1
fi

# Search for the function in each path
for path in "${library_paths[@]}"; do
    if [ -d "$path" ]; then
        # Find shared libraries and apply nm
        find "$path" -type f -name "*.so*" -exec sh -c "nm -D {}  2>/dev/null | grep -i '$function_name' && echo {}" \;
    fi
done

Make sure to run this script from a terminal where nm is available and you have the necessary permissions to access the library directories. The script will output the paths of the libraries that contain the specified function. Since grep is only used after nm, the performance should be reasonable, but this will also depend on the number of libraries and the size of the directories being searched.

Please note that this script may take some time to execute since it searches through all specified directories and their subdirectories for shared libraries. Also, it's important to ensure that you have read permissions for the directories you are searching.

Note that I have added the current directory (".") to the search directories list, which means the script will also check for shared libraries in the directory from which the script is run.

Answered By - zzami

Answer Checked By - Timothy Miller (WPSolving Admin)