135

I am getting the following error:

WindowsError: [Error 2] The system cannot find the file specified

My code is:

subprocess.call(["<<executable file found in PATH>>"])

Windows 7, 64 bit. Python 3.x latest, stable.

Any ideas?

Thanks,

SilentGhost
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Sri
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  • and what is this executable file? – SilentGhost Jun 11 '10 at 10:31
  • The "android" executable part of the Android SDK – Sri Jun 11 '10 at 10:32
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    And is *is* available on PATH – Sri Jun 11 '10 at 10:33
  • can you run it from the command line? – SilentGhost Jun 11 '10 at 10:34
  • A little background of what I'm trying to accomplish. This is for Opendevice - an open source project to convert HTML5 apps into device specific apps. I'm trying to replace os.system() in http://bitbucket.org/srirangan/opendevice/src/tip/tools/net/srirangan/opendevice/plugins/AndroidPlugin.py to subprocess.call() – Sri Jun 11 '10 at 10:35
  • @SilentGhost: Yes I can run it from the command line. os.sys("...") calls in Python also work. – Sri Jun 11 '10 at 10:35
  • If the path has spaces, is it quoted? And of course, you escaped backslashes properly, or used slashes, right? – Ryan Ginstrom Jun 11 '10 at 10:42

7 Answers7

219

When the command is a shell built-in, add a shell=True to the call.

E.g. for dir you would type:

import subprocess
subprocess.call('dir', shell=True)

To quote from the documentation:

The only time you need to specify shell=True on Windows is when the command you wish to execute is built into the shell (e.g. dir or copy). You do not need shell=True to run a batch file or console-based executable.

phoenix
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Douglas Macdonald
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    That's because there's no executable called `dir.exe` while there's a `/bin/ls` in *nix. `dir` is implemented by _CMD.EXE_ much like `cd` is implemented by _bash_. – Apalala Jan 06 '11 at 16:45
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    This is strongly discouraged. https://docs.python.org/2/library/subprocess.html#frequently-used-arguments – nu everest Feb 13 '16 at 15:18
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    @nueverest Only when the _the command string is constructed from external input_ – Jirka Jul 22 '16 at 16:59
  • The alternative (more secure for external input) is to get the `PATH` from the `os.environ` and search it manually. – asmeurer Jul 10 '17 at 02:18
48

On Windows, I believe the subprocess module doesn't look in the PATH unless you pass shell=True because it use CreateProcess() behind the scenes. However, shell=True can be a security risk if you're passing arguments that may come from outside your program. To make subprocess nonetheless able to find the correct executable, you can use shutil.which. Suppose the executable in your PATH is named frob:

subprocess.call([shutil.which('frob'), arg1, arg2])

(This works on Python 3.3 and above.)

Anon
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ptomato
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    Any python 2 option? – Naramsim Mar 19 '18 at 08:49
  • @Naramsim Try `from distutils.spawn import find_executable as which`. This line is copied from pre-commit's hook script. – Allan Chain Aug 14 '21 at 10:45
  • This is not correct. The system examines the `PATH` even without `shell=True` but shell built-ins like `cd` and `dir` are not available on the `PATH` because they are not executables at all. That's what being built into the shell means; the command is understood and executed by the shell itself, and does not exist as a separate binary. – tripleee Oct 28 '22 at 12:44
27

On Windows you have to call through cmd.exe. As Apalala mentioned, Windows commands are implemented in cmd.exe not as separate executables.

e.g. 

subprocess.call(['cmd', '/c', 'dir'])

/c tells cmd to run the follow command

This is safer than using shell=True, which allows shell injections.

Sam Inverso
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3

If you are using powershell, then in it will be subprocess.call(['powershell','-command','dir']). Powershell supports a large portion of POSIX commands

Alexander Nozik
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2

After much head scratching, I discovered that running a file that is located in C:\Windows\System32\ while running a 32bit version of python on a 64bit machine is a potential issue, due to Windows trying to out-smart the process, and redirect calls to C:\Windows\System32 to C:\Windows\SysWOW64.

I found an example of how to fix this here: http://code.activestate.com/recipes/578035-disable-file-system-redirector/

RBN
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0

To quote from the documentation:

"Prior to Python 3.5, these three functions comprised the high level API to subprocess. You can now use run() in many cases, but lots of existing code calls these functions."

SO: instead of subprocess.call use subprocess.run for Python 3.5 and above

Adrian Berca
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I met the same issue while I was calling a PHP. The reason is PHP isn't in PATH so the command PHP was not found. But PowerShell found it does exist in the current location and it suggests replacing the 'PHP' by the '.\PHP' if I trust this command. Then it runs well.

michael xie
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