1#!/usr/bin/env python
2
3"""CaptureCmd - A generic tool for capturing information about the
4invocations of another program.
5
6Usage
7--
81. Move the original tool to a safe known location.
9
102. Link CaptureCmd to the original tool's location.
11
123. Define CAPTURE_CMD_PROGRAM to the known location of the original
13tool; this must be an absolute path.
14
154. Define CAPTURE_CMD_DIR to a directory to write invocation
16information to.
17"""
18
19import hashlib
20import os
21import sys
22import time
23
24def saveCaptureData(prefix, dir, object):
25    string = repr(object) + '\n'
26    key = hashlib.sha1(string).hexdigest()
27    path = os.path.join(dir,
28                        prefix + key)
29    if not os.path.exists(path):
30        f = open(path, 'wb')
31        f.write(string)
32        f.close()
33    return prefix + key
34
35def main():
36    program = os.getenv('CAPTURE_CMD_PROGRAM')
37    dir = os.getenv('CAPTURE_CMD_DIR')
38    fallback = os.getenv('CAPTURE_CMD_FALLBACK')
39    if not program:
40        raise ValueError('CAPTURE_CMD_PROGRAM is not defined!')
41    if not dir:
42        raise ValueError('CAPTURE_CMD_DIR is not defined!')
43
44    # Make the output directory if it doesn't already exist.
45    if not os.path.exists(dir):
46        os.mkdir(dir, 0700)
47
48    # Get keys for various data.
49    env = os.environ.items()
50    env.sort()
51    envKey = saveCaptureData('env-', dir, env)
52    cwdKey = saveCaptureData('cwd-', dir, os.getcwd())
53    argvKey = saveCaptureData('argv-', dir, sys.argv)
54    entry = (time.time(), envKey, cwdKey, argvKey)
55    saveCaptureData('cmd-', dir, entry)
56
57    if fallback:
58        pid = os.fork()
59        if not pid:
60            os.execv(program, sys.argv)
61            os._exit(1)
62        else:
63            res = os.waitpid(pid, 0)
64            if not res:
65                os.execv(fallback, sys.argv)
66                os._exit(1)
67            os._exit(res)                
68    else:
69        os.execv(program, sys.argv)
70        os._exit(1)
71
72if __name__ == '__main__':
73    main()
74