Question

I write a function which sets system time in linux. I write next code:

import time
import subprocess

def SetSystemTime(val):        
    try:
        val = float(val)
    except ValueError:
        return
    command = 'date -s"' + time.ctime(val) + '"'
    subprocess.call(command)

On calling of that i get:

File “crc.py”, line 96, in
SetSystemTime(0)
File “crc.py”, line 12, in SetSystemTime
subprocess.call(command)
File “/usr/lib/python2.7/subprocess.py”, line 493, in call
return Popen(*popenargs, **kwargs).wait()
File “/usr/lib/python2.7/subprocess.py”, line 679, in init
errread, errwrite)
File “/usr/lib/python2.7/subprocess.py”, line 1239, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory

Answer 1

subprocess.call() normally takes a list of strings as its first argument. If you hand it a string X (as you do), that one will be converted to list with that whole string as its first argument.
The first element of that list is executed with the rest of that list as arguments.
So the underlying OS tries to execute the executable ‘date -s”XXYYXXZ”‘ and cannot find it.

This is different from os.system() that hands the parameter to a shell that most often splits the string it gets at the spaces and then executes the first element split off.

Try:

command = ['date', '-s"' + time.ctime(val) + '"']
subprocess.call(command)

as the last two lines.