Macher

Macher is a command line tool for inspecting and modifying Mach-O binary files as produced by Apple's clang C compiler.

Macher provides some functions which are similar to those provided by Apple's install_name_tool and otool programs, as well as some functions which are not available with those programs.

When running macher in a shell the general format is:

$ macher [-options] <command> <command args>...

The only option is -v or --verbose, which adds additional output compared to what is available without this option.

Here is a list of the available commands:

help

$ macher help

Prints usage information.

version

$ macher version

Prints the version number.

segments

$ macher [-options] segments <Mach-O file path>

Prints information about each segment in the Mach-O file. In verbose mode, the sections within each segment are listed.

commands

$ macher [-options] commands <Mach-O file path>

Prints information about each load command in the Mach-O file. This includes the load commands which define segments. The verbose mode provides additional details about the commands. This is similar to otool -l but generates output which is more readable and amenable to being parsed by a script.

append

$ macher [-options] append <Mach-O file path> <data file path> <output path>

Creates a fat binary by adding a new slice containing arbitrary data at the end of a Mach-O file. The new slice is tagged for the "any" architecture and is guaranteed to be the last slice in the fat binary.

The main purpose of this command is to make it possible to produce a Zip self-extracting archive without creating an invalid Mach-O binary file. Simply appending a Zip file to the end of a thin or fat binary corrupts the Mach-O structure by causing the __LINKEDIT segment of the last slice not to extend to the end of the file as required.

After appending a Zip file, the zip -A command should be used to adjust the offset tables within the Zip data. After doing this, the files in the zip archive can be exracted by calling unzip as if the fat binary were an ordinary zip archive.

add_rpath

$ macher [-options] add_rpath <library search path> <Mach-O file path>

Adds an LC_RPATH load command with the specified search path. This is equivalent to install_name_tool -add_rpath except that it will not add the load command if there already exists an LC_RPATH load command with the same path.

This action also removes all LC_CODE_SIGNATURE load commands.

If there is a LC_DYLIB command containing the substring @rpath then the loader will search for the library in all paths obtained by replacing @rpath by one of the paths given in LC_RPATH load commands.

remove_rpath

$ macher [-options] remove_rpath <library search path> <Mach-O file path>

Removes all LC_RPATH load commands specifying the given search path.

This action also removes all LC_CODE_SIGNATURE load commands.

clear_rpaths

$ macher [-options] clear_rpaths <Mach-O file path>

Removes all LC_RPATH load commands.

This action also removes all LC_CODE_SIGNATURE load commands.

remove_signature

$ macher [-options] remove_signature <Mach-O file path>

Removes all LC_CODE_SIGNATURE load commands.

edit_libpath

$ macher [-options] edit_libpath <old path> <new path> <Mach-O file path> $ macher [-options] edit_libpath <new path> <Mach-O file path>

With three arguments,searches for an LC_DYLIB load command for which the dylib path is the specified old path. If one is found, the dylib path in the command is replaced by the new path. This is equivalent to install_name_tool -change.

With two arguments this command is similar to install_name_tool -change but it does not require that you provide the exact old dylib path. It uses the file name of the old path to decide whether to do the replacement.

This action also removes all LC_CODE_SIGNATURE load commands.

set_id

$ macher [-options] set_id <dylib id> <Mach-O file path>

Sets the path in the LC_ID_DYLIB load command to the specified path. The LC_ID_DYLIB load command exists only for dylib files. When another executable is linked with the dylib, the linker copies the id into an LC_DYLIB command for the executable.

This action also removes all LC_CODE_SIGNATURE load commands.