如何编写自定义ls命令并在已Root安卓终端运行及C代码部署疑问

Great job getting your custom ls code written! Let's walk through how to get it running on your rooted Android device, and answer your question about deploying to /system/bin.

First: Compile Your C Code for Android #

Android uses different CPU architectures (most commonly ARM64 or 32-bit ARM) than desktop x86 systems, so you need to compile your code to match your device's hardware. Here are two straightforward ways:

Option 1: Cross-Compile on a Desktop (Linux/macOS) #

1. Grab the Android NDK (Native Development Kit) — you can get it via Android Studio or as a standalone download.
2. Identify your device's architecture: Run uname -m in a rooted terminal (output like aarch64 for ARM64, armv7l for 32-bit ARM).
3. Use the NDK's toolchain to compile:
   • For ARM64: aarch64-linux-android29-clang your_ls.c -o custom_ls (replace 29 with your device's Android API level if needed)
   • For 32-bit ARM: armv7a-linux-androideabi29-clang your_ls.c -o custom_ls

Option 2: Compile Directly on Android (Easier for Testing) #

Use Termux, a powerful terminal emulator for Android:

1. Install Termux from F-Droid (the Google Play version is outdated).
2. Open Termux and install the compiler: pkg install clang
3. Copy your C code into Termux's storage: cp /sdcard/your_ls.c ~/
4. Compile: clang your_ls.c -o custom_ls

Deploy the Binary to Your Rooted Device #

If you cross-compiled on a desktop, transfer the binary to your device via ADB:
adb push custom_ls /sdcard/

Install It to /system/bin (Or Run It Directly) #

Your question: Is putting it in /system/bin enough? Mostly yes, but there are critical steps to make it work properly:

1. Gain root access: Open your terminal emulator and run su (grant root permissions when prompted).
2. Remount /system as read-write: By default, /system is read-only to protect system files. Run:
   mount -o rw,remount /system
   Note: Some newer devices use /system_root instead — check with mount | grep /system if this fails.
3. Copy the binary:
   cp /sdcard/custom_ls /system/bin/ (adjust the source path if you compiled in Termux, e.g., cp ~/custom_ls /system/bin/)
4. Set correct permissions: The binary needs to be executable by all users:
   chmod 755 /system/bin/custom_ls
5. Remount /system back to read-only: Restore the device's default security state:
   mount -o ro,remount /system

Run Your Custom ls #

Now, open any terminal emulator (rooted or not) and type custom_ls — it should run just like the built-in ls command!

Alternative: Run Without Modifying /system #

If you don't want to alter the system directory, you can run the binary directly:

• Navigate to its folder: cd /sdcard/
• Execute it: ./custom_ls
  Or add its path to your PATH temporarily: export PATH=$PATH:/sdcard/, then just type custom_ls.

Troubleshooting Tips #

• "Exec format error": Your binary's architecture doesn't match your device's. Double-check the compiler toolchain you used.
• "Permission denied": Ensure you set 755 permissions, and temporarily disable SELinux if needed: su -c setenforce 0 (note: this reduces security, so only use for testing).
• Unexpected behavior: Android uses Bionic libc, which is mostly POSIX-compliant but has minor differences from glibc. Verify your code uses Android-compatible functions.

内容的提问来源于stack exchange，提问作者NoNoob