examples: add command_with_chroot.c.v

examples/command_with_chroot.c.v

@@ -0,0 +1,68 @@
+/*
+	Note: chroot() call requires privilege escalation in the operating system.
+	Therefore, to run this example, run: `sudo v run command_with_chroot.c.v`
+*/
+import os
+import runcmd
+import term
+
+fn C.chroot(&char) i32
+
+fn main() {
+	// Create new root filesystem for demonstration.
+	new_root := '/tmp/new_root'
+
+	// Create dirtree and copy `ls` utility with shared objects...
+	paths := {
+		0: os.join_path(new_root, 'usr', 'bin')
+		1: os.join_path(new_root, 'usr', 'lib')
+		2: os.join_path(new_root, 'lib64')
+	}
+	for _, path in paths {
+		os.mkdir_all(path)!
+	}
+	os.cp('/usr/bin/ls', paths[0])!
+	os.cp('/usr/lib/libcap.so.2', paths[1])!
+	os.cp('/usr/lib/libc.so.6', paths[1])!
+	os.cp('/lib64/ld-linux-x86-64.so.2', paths[2])!
+
+	// Create a test file in the new root.
+	os.write_file(os.join_path_single(new_root, 'HELLO_FROM_CHROOT'), 'TEST')!
+
+	// Cleanup demo root filesystem at exit.
+	defer {
+		os.rmdir_all(new_root) or {}
+	}
+
+	// Prepare the command.
+	mut cmd := runcmd.new('ls', '-alFh', '/')
+
+	// Add pre-exec hook to perform chroot().
+	cmd.pre_exec_hooks << fn [new_root] (mut p runcmd.Process) ! {
+		if C.chroot(&char(new_root.str)) == -1 {
+			return os.last_error()
+		}
+	}
+
+	// Run command and read its output.
+	out := cmd.output() or {
+		if err is runcmd.ExitError {
+			eprintln(err)
+			exit(err.code())
+		} else {
+			panic(err)
+		}
+	}
+
+	// Expected output:
+	//
+	// total 4.0K
+	// drwxr-xr-x 4 0 0 100 Jan  8 06:39 ./
+	// drwxr-xr-x 4 0 0 100 Jan  8 06:39 ../
+	// -rw-r--r-- 1 0 0   4 Jan  8 06:39 HELLO_FROM_CHROOT
+	// drwxr-xr-x 2 0 0  60 Jan  8 06:39 lib64/
+	// drwxr-xr-x 4 0 0  80 Jan  8 06:39 usr/
+
+	println('Command output: ${term.yellow(out)}')
+	println('Child state: ${cmd.state}')
+}