macOS

rltyty included in IT

2025-07-28 229 words

Contents

Toolchains

Print macOS developer directory active in use

xcode-select -p

Select toochains

sudo xcode-select --switch /Library/Developer/CommandLineTools
sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
sudo xcode-select -r                    # (reset to default)

Toolchains installed from CommandLineTools (CLT) are used for general c/c++ application development:

/Library/Developer/CommandLineTools/usr/{bin,include,lib}
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/{bin,include,lib}

The toolchains installed from Xcode for macOS/iOS/tvOS application development:

/Applications/Xcode.app/Contents/Developer

Show macOS SDK path

xcrun --sdk macosx --show-sdk-path

Use gcc/clang to check “include” search pathes on both macOS and Linux

gcc/clang -xc -E -v -

Use search manual pathes of SDK

find $(xcode-select -p) -type d | /usr/bin/grep '/usr/share/man$' | /usr/bin/tr -s '\n' ':'; echo

New shared library .tbd files

.tbd files are text-based stub libraries (to reduce download size), which points to the real binary .dylib files under

/usr/lib/system/libSystem_*.dylib

In newer macOS, shared libs are merged into a single binary

/System/Library/dyld/dyld_shared_cache_x86_64

A tool (brew install keith/formulae/dyld-shared-cache-extractor) can be used to extract it to separated .dylib files.

dyld-shared-cache-extractor dyld_shared_cache_x86_64 ~/tmp/libs

Examples of separated libs:
- Standard C lib

~/tmp/libs/usr/lib/system/libsystem_c.dylib

Standard C math lib

~/tmp/libs/usr/lib/system/libsystem_m.dylib

pthreads lib

~/tmp/libs/usr/lib/system/libsystem_pthread.dylib

Service Manager

Concept	Linux	macOS
Init system / Service manager	`systemd`	`launchd`
CLI tool	`systemctl`	`launchctl`
Service definition	`*.service` unit files	`*.plist` property list files
User service location	`~/.config/systemd/user/`	`~/Library/LaunchAgents/`
System service location	`/etc/systemd/system/`	`/Library/LaunchDaemons/`
Starts at boot	`systemctl enable`	Auto-loaded based on `plist` location and `RunAtLoad` or `KeepAlive` keys
Start/stop manually	`systemctl start/stop`	`launchctl start/stop`
List services	`systemctl list-units`	`launchctl list`