Cat remote file over ssh (with pretzel framework)

pretzel_cat.py

"""Cat remote file over ssh

pretzel framework: https://github.com/aslpavel/pretzel
"""
from __future__ import print_function
import os
import sys
from pretzel.app import app
from pretzel.monad import async
from pretzel.remoting import SSHConnection

SIZE_LIMIT = 1 << 20  # 1Mb


@app
def main():
    """Read remote file
    """
    if len(sys.argv) < 3:
        sys.stderr.write('usage: {} <host> <path>\n'.format(sys.argv[0]))
        sys.exit(1)

    host = sys.argv[1]
    path = sys.argv[2]
    with (yield SSHConnection(host)) as ssh:  # create and connect
        # ssh(target) returns targets proxy object. When proxy object is awaited
        # request is send to remote side and executed. All exception are
        # marshaled.

        # check file access
        if not (yield ssh(os.access)(path, os.R_OK)):
            sys.stderr.write('[error] no such file: {}\n'.format(path))
            sys.exit(1)

        # check file size
        size = yield ssh(os.path.getsize)(path)
        if size > SIZE_LIMIT:
            sys.stderr.write('[error] file is too big: {}\n'.format(size))
            sys.exit(1)

        # read file
        print((yield ssh(open)(path).read()))


if __name__ == '__main__':
    main()