Apc

.travis.yml

@@ -0,0 +1,12 @@
+language: python
+python:
+    - 2.7
+    - 3.3
+    - 3.4
+    - 3.5
+
+before_install:
+    - pip install pep8
+
+script:
+    - find . -name \*.py -exec pep8 {} +

CHANGES.md

@@ -1,3 +1,11 @@
+2016-08-01, Version 0.2.0
+=========================
+* Add `export` built-in command (Yuliang Tan)
+* Add `getenv` built-in command (Yuliang Tan)
+* Use subprocess module to fork and exec (Yuliang Tan)
+* Get an environment variable if a token begins with a dollar sign (Yuliang Tan)
+* Support Windows (Yuliang Tan)
+
 2016-07-08, Version 0.1.0
 =========================
 * Add main shell lopp (Supasate Choochaisri)

README.md

@@ -2,4 +2,4 @@
 
 A simple shell written in Python
 
-The implementation details can be found at **Create Your Own Shell in Python** [Part I](https://hackercollider.com/articles/2016/07/05/create-your-own-shell-in-python-part-1/) and [Part II](https://hackercollider.com/articles/2016/07/06/create-your-own-shell-in-python-part-2/)
+> Note: If you found this repo from the article **Create Your Own Shell in Python** [Part I](https://hackercollider.com/articles/2016/07/05/create-your-own-shell-in-python-part-1/) and [Part II](https://hackercollider.com/articles/2016/07/06/create-your-own-shell-in-python-part-2/), you can check out the `tutorial` branch for the source code used in the article.

setup.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+
+from setuptools import setup
+
+setup(name='yosh',
+      version='1.0',
+      description='Your own shell',
+      author='Supasate Choochaisri',
+      author_email='[email protected]',
+      url='https://github.com/supasate/yosh',
+      packages=['yosh', 'yosh.builtins'],
+      entry_points="""
+      [console_scripts]
+      yosh = yosh.shell:main
+      """,
+      )

yosh/builtins/__init__.py

@@ -1,2 +1,5 @@
 from yosh.builtins.cd import cd
 from yosh.builtins.exit import exit
+from yosh.builtins.export import export
+from yosh.builtins.getenv import getenv
+from yosh.builtins.history import history

yosh/builtins/cd.py

@@ -3,5 +3,8 @@
 
 
 def cd(args):
-    os.chdir(args[0])
+    if len(args) > 0:
+        os.chdir(args[0])
+    else:
+        os.chdir(os.getenv('HOME'))
     return SHELL_STATUS_RUN

yosh/builtins/export.py

@@ -0,0 +1,9 @@
+import os
+from yosh.constants import *
+
+
+def export(args):
+    if len(args) > 0:
+        var = args[0].split('=', 1)
+        os.environ[var[0]] = var[1]
+    return SHELL_STATUS_RUN

yosh/builtins/getenv.py

@@ -0,0 +1,8 @@
+import os
+from yosh.constants import *
+
+
+def getenv(args):
+    if len(args) > 0:
+        print(os.getenv(args[0]))
+    return SHELL_STATUS_RUN

yosh/builtins/history.py

@@ -0,0 +1,24 @@
+import os
+import sys
+from yosh.constants import *
+
+
+def history(args):
+    with open(HISTORY_PATH, 'r') as history_file:
+        lines = history_file.readlines()
+
+        # default limit is whole file
+        limit = len(lines)
+
+        if len(args) > 0:
+            limit = int(args[0])
+
+        # start history line to print out
+        start = len(lines) - limit
+
+        for line_num, line in enumerate(lines):
+            if line_num >= start:
+                sys.stdout.write('%d %s' % (line_num + 1, line))
+        sys.stdout.flush()
+
+    return SHELL_STATUS_RUN

yosh/constants.py

@@ -1,2 +1,5 @@
+import os
+
 SHELL_STATUS_STOP = 0
 SHELL_STATUS_RUN = 1
+HISTORY_PATH = os.path.expanduser('~') + os.sep + '.yosh_history'

yosh/shell.py

@@ -1,6 +1,11 @@
 import os
 import sys
 import shlex
+import getpass
+import socket
+import signal
+import subprocess
+import platform
 from yosh.constants import *
 from yosh.builtins import *
 
@@ -12,56 +17,104 @@ def tokenize(string):
     return shlex.split(string)
 
 
-def execute(cmd_tokens):
-    # Extract command name and arguments from tokens
-    cmd_name = cmd_tokens[0]
-    cmd_args = cmd_tokens[1:]
-
-    # If the command is a built-in command, invoke its function with arguments
-    if cmd_name in built_in_cmds:
-        return built_in_cmds[cmd_name](cmd_args)
-
-    # Fork a child shell process
-    # If the current process is a child process, its `pid` is set to `0`
-    # else the current process is a parent process and the value of `pid`
-    # is the process id of its child process.
-    pid = os.fork()
-
-    if pid == 0:
-        # Child process
-        # Replace the child shell process with the program called with exec
-        os.execvp(cmd_tokens[0], cmd_tokens)
-    elif pid > 0:
-        # Parent process
-        while True:
-            # Wait response status from its child process (identified with pid)
-            wpid, status = os.waitpid(pid, 0)
-
-            # Finish waiting if its child process exits normally or is
-            # terminated by a signal
-            if os.WIFEXITED(status) or os.WIFSIGNALED(status):
-                break
+def preprocess(tokens):
+    processed_token = []
+    for token in tokens:
+        # Convert $-prefixed token to value of an environment variable
+        if token.startswith('$'):
+            processed_token.append(os.getenv(token[1:]))
+        else:
+            processed_token.append(token)
+    return processed_token
+
+
+def handler_kill(signum, frame):
+    raise OSError("Killed!")
+
 
+def execute(cmd_tokens):
+    with open(HISTORY_PATH, 'a') as history_file:
+        history_file.write(' '.join(cmd_tokens) + os.linesep)
+
+    if cmd_tokens:
+        # Extract command name and arguments from tokens
+        cmd_name = cmd_tokens[0]
+        cmd_args = cmd_tokens[1:]
+
+        # If the command is a built-in command,
+        # invoke its function with arguments
+        if cmd_name in built_in_cmds:
+            return built_in_cmds[cmd_name](cmd_args)
+
+        # Wait for a kill signal
+        signal.signal(signal.SIGINT, handler_kill)
+        # Spawn a child process
+        if platform.system() != "Windows":
+            # Unix support
+            p = subprocess.Popen(cmd_tokens)
+            # Parent process read data from child process
+            # and wait for child process to exit
+            p.communicate()
+        else:
+            # Windows support
+            command = ""
+            for i in cmd_tokens:
+                command = command + " " + i
+            os.system(command)
     # Return status indicating to wait for next command in shell_loop
     return SHELL_STATUS_RUN
 
 
-def shell_loop():
-    status = SHELL_STATUS_RUN
+# Display a command prompt as `[<user>@<hostname> <dir>]$ `
+def display_cmd_prompt():
+    # Get user and hostname
+    user = getpass.getuser()
+    hostname = socket.gethostname()
 
-    while status == SHELL_STATUS_RUN:
-        # Display a command prompt
-        sys.stdout.write('> ')
-        sys.stdout.flush()
+    # Get base directory (last part of the curent working directory path)
+    cwd = os.getcwd()
+    base_dir = os.path.basename(cwd)
 
-        # Read command input
-        cmd = sys.stdin.readline()
+    # Use ~ instead if a user is at his/her home directory
+    home_dir = os.path.expanduser('~')
+    if cwd == home_dir:
+        base_dir = '~'
 
-        # Tokenize the command input
-        cmd_tokens = tokenize(cmd)
+    # Print out to console
+    sys.stdout.write("[%s@%s %s]$ " % (user, hostname, base_dir))
+    sys.stdout.flush()
 
-        # Execute the command and retrieve new status
-        status = execute(cmd_tokens)
+
+def ignore_signals():
+    # Ignore Ctrl-Z stop signal
+    if platform.system() != "Windows":
+        signal.signal(signal.SIGTSTP, signal.SIG_IGN)
+    # Ignore Ctrl-C interrupt signal
+    signal.signal(signal.SIGINT, signal.SIG_IGN)
+
+
+def shell_loop():
+    status = SHELL_STATUS_RUN
+
+    while status == SHELL_STATUS_RUN:
+        display_cmd_prompt()
+
+        # Ignore Ctrl-Z and Ctrl-C signals
+        ignore_signals()
+
+        try:
+            # Read command input
+            cmd = sys.stdin.readline()
+            # Tokenize the command input
+            cmd_tokens = tokenize(cmd)
+            # Preprocess special tokens
+            # (e.g. convert $<env> into environment value)
+            cmd_tokens = preprocess(cmd_tokens)
+            # Execute the command and retrieve new status
+            status = execute(cmd_tokens)
+        except:
+            _, err, _ = sys.exc_info()
+            print(err)
 
 
 # Register a built-in function to built-in command hash map
@@ -73,6 +126,9 @@ def register_command(name, func):
 def init():
     register_command("cd", cd)
     register_command("exit", exit)
+    register_command("export", export)
+    register_command("getenv", getenv)
+    register_command("history", history)
 
 
 def main():