Add "occlum new" command

README.md

@@ -30,12 +30,16 @@ Hello World
 ```
 Note that the Occlum toolchain is not cross-compiling in the traditional sense: the binaries built by the Occlum toolchain is also runnable on Linux. This property makes it convenient to compile, debug, and test user programs intended for Occlum.
 
-**Step 2. Initialize a directory as the Occlum instance via `occlum init`**
+**Step 2. Initialize a directory as the Occlum instance via `occlum init` or `occlum new`**
 ```
 $ mkdir occlum_instance && cd occlum_instance
 $ occlum init
 ```
-The `occlum init` command creates the compile-time and run-time state of Occlum in the current working directory. Each Occlum instance directory should be used for a single instance of an application; multiple applications or different instances of a single application should use different Occlum instances.
+or
+```
+$ occlum new occlum_instance
+```
+The `occlum init` command creates the compile-time and run-time state of Occlum in the current working directory. The `occlum new` command does basically the same thing but in a new instance diretory. Each Occlum instance directory should be used for a single instance of an application; multiple applications or different instances of a single application should use different Occlum instances.
 
 **Step 3. Generate a secure Occlum FS image and Occlum SGX enclave via `occlum build`**
 ```

src/pal/include/occlum_pal_api.h

@@ -21,7 +21,7 @@ int occlum_pal_get_version(void);
  * Occlum PAL attributes
  */
 typedef struct occlum_pal_attr {
-	// Occlum instance directory.
+    // Occlum instance directory.
     //
     // Specifies the path of an Occlum instance directory, which is usually created with the
     // `occlum new` command. The default value is "."; that is, the current working directory

tools/occlum

@@ -34,8 +34,11 @@ report_arg_error() {
     echo ""
     cat <<EOF
 Usage:
+    occlum new <path>
+        Create a new directory at <path> and initialize as the Occlum instance.
+
     occlum init
-        Initialize a directory as the Occlum instance
+        Initialize a directory as the Occlum instance.
 
     occlum build [--sign-key <key_path>] [--sign-tool <tool_path>] [-f/--force]
         Build and sign an Occlum SGX enclave (.so) and generate its associated secure FS image
@@ -70,6 +73,28 @@ check_has_built() {
 }
 
 
+cmd_new() {
+    if [ -z $@ ]; then
+        echo "Error: target directory is not set"
+        exit 1
+    fi
+
+    dir_path="$@"
+    if [[ "$dir_path" != "/"* ]]; then
+        dir_path="$instance_dir/$@"
+    fi
+
+    if [[ -e "$dir_path" ]]; then
+        echo "Error: destination \"$dir_path\" already exists"
+        exit 1
+    fi
+
+    mkdir -p $dir_path
+    instance_dir=$dir_path
+    status_file=$instance_dir/.__occlum_status
+    cd $dir_path && cmd_init
+}
+
 cmd_init() {
     if [ -f "$status_file"  ]; then
         echo "Error: the current working directory has been initialized as an Occlum instance"
@@ -261,6 +286,9 @@ fi
 
 cmd=$1
 case "$cmd" in
+    new)
+        cmd_new "${@:2:1}"
+        ;;
     init)
         cmd_init
         ;;