Read/Write from/to a process

[jas]

Hi,
I would like to start a new process and be able to read/write from/to
it. I have tried things like...

import subprocess as sp
p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
p.stdin.write(" hostname\n")

however, it doesn't seem to work. I think the cmd.exe is catching it.

I also tried
f = open("out.txt", "w")
sys.stdout = f
os.system("cmd. exe")

...but out.txt didn't contain any output from cmd.exe

So, how can I create a process (in this case, cmd.exe) on Windows and
be able to read/write from/to it?

Thanks

[Dennis Lee Bieber]

Re: Read/Write from/to a process

On 24 Oct 2005 07:20:42 -0700, "jas" <codecraig@gmai l.com> declaimed the
following in comp.lang.pytho n:
[color=blue]
> Hi,
> I would like to start a new process and be able to read/write from/to
> it. I have tried things like...
>
> import subprocess as sp
> p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
> p.stdin.write(" hostname\n")
>
> however, it doesn't seem to work. I think the cmd.exe is catching it.[/color]

One: you didn't read any of the "returned" output...

Two: the output only seems to be available upon EOF, which means the
spawned command processor has to exit first... Though you CAN read one
character at a time, and then have to build lines and expected prompt
strings...


This seems to work:
-=-=-=-=-=-=-=-=-
import subprocess
import os

PROMPT = os.getcwd() + ">"

def getLine(proc):
ld = []
while True:
c = proc.stdout.rea d(1)
if c == "\r": continue #skip Windows <cr>
if c != "\n": ld.append(c) #save all but <lf>
if c is None or c == "\n" or c == ">": break
ln = "".join(ld)
return ln

p = subprocess.Pope n("cmd.exe", stdout=subproce ss.PIPE, stdin =
subprocess.PIPE )

print "**** START of captured output"
while True:
ln = getLine(p)
print ln
if ln == PROMPT: break
print "**** END of captured output"

p.stdin.write(" ipconfig\n")
print "**** START of captured output"
while True:
ln = getLine(p)
print ln
if ln == PROMPT: break
print "**** END of captured output"

p.stdin.write(" dir\n")
print "**** START of captured output"
while True:
ln = getLine(p)
print ln
if ln == PROMPT: break
print "**** END of captured output"

p.stdin.write(" exit\n")
-=-=-=-=-=-=-=-=-=-
E:\UserData\Den nis Lee Bieber\My Documents>pytho n script1.py
**** START of captured output
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

E:\UserData\Den nis Lee Bieber\My Documents>
**** END of captured output
**** START of captured output
ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.1.100
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IP Address. . . . . . . . . . . . : fe80::211:11ff: fee1:f303%4
Default Gateway . . . . . . . . . : 192.168.1.1

Tunnel adapter Teredo Tunneling Pseudo-Interface:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . :
3ffe:831f:4004: 1956:0:fbde:bd0 a:e50b
IP Address. . . . . . . . . . . . : fe80::5445:5245 :444f%5
Default Gateway . . . . . . . . . : ::

Tunnel adapter Automatic Tunneling Pseudo-Interface:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : fe80::5efe:192. 168.1.100%2
Default Gateway . . . . . . . . . :

E:\UserData\Den nis Lee Bieber\My Documents>
**** END of captured output
**** START of captured output
dir
Volume in drive E is Data
Volume Serial Number is 2626-D991

Directory of E:\UserData\Den nis Lee Bieber\My Documents

10/24/2005 09:23 AM <DIR>

[jas]

Re: Read/Write from/to a process

Thanks, that is certainly a start. As you mentioned, the "cd" could is
an issue.

Perhaps checking to see if the line ends with ">" is sufficient?

Dennis Lee Bieber wrote:[color=blue]
> On 24 Oct 2005 07:20:42 -0700, "jas" <codecraig@gmai l.com> declaimed the
> following in comp.lang.pytho n:
>[color=green]
> > Hi,
> > I would like to start a new process and be able to read/write from/to
> > it. I have tried things like...
> >
> > import subprocess as sp
> > p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
> > p.stdin.write(" hostname\n")
> >
> > however, it doesn't seem to work. I think the cmd.exe is catching it.[/color]
>
> One: you didn't read any of the "returned" output...
>
> Two: the output only seems to be available upon EOF, which means the
> spawned command processor has to exit first... Though you CAN read one
> character at a time, and then have to build lines and expected prompt
> strings...
>
>
> This seems to work:
> -=-=-=-=-=-=-=-=-
> import subprocess
> import os
>
> PROMPT = os.getcwd() + ">"
>
> def getLine(proc):
> ld = []
> while True:
> c = proc.stdout.rea d(1)
> if c == "\r": continue #skip Windows <cr>
> if c != "\n": ld.append(c) #save all but <lf>
> if c is None or c == "\n" or c == ">": break
> ln = "".join(ld)
> return ln
>
> p = subprocess.Pope n("cmd.exe", stdout=subproce ss.PIPE, stdin =
> subprocess.PIPE )
>
> print "**** START of captured output"
> while True:
> ln = getLine(p)
> print ln
> if ln == PROMPT: break
> print "**** END of captured output"
>
> p.stdin.write(" ipconfig\n")
> print "**** START of captured output"
> while True:
> ln = getLine(p)
> print ln
> if ln == PROMPT: break
> print "**** END of captured output"
>
> p.stdin.write(" dir\n")
> print "**** START of captured output"
> while True:
> ln = getLine(p)
> print ln
> if ln == PROMPT: break
> print "**** END of captured output"
>
> p.stdin.write(" exit\n")
> -=-=-=-=-=-=-=-=-=-
> E:\UserData\Den nis Lee Bieber\My Documents>pytho n script1.py
> **** START of captured output
> Microsoft Windows XP [Version 5.1.2600]
> (C) Copyright 1985-2001 Microsoft Corp.
>
> E:\UserData\Den nis Lee Bieber\My Documents>
> **** END of captured output
> **** START of captured output
> ipconfig
>
> Windows IP Configuration
>
>
> Ethernet adapter Local Area Connection:
>
> Connection-specific DNS Suffix . :
> IP Address. . . . . . . . . . . . : 192.168.1.100
> Subnet Mask . . . . . . . . . . . : 255.255.255.0
> IP Address. . . . . . . . . . . . : fe80::211:11ff: fee1:f303%4
> Default Gateway . . . . . . . . . : 192.168.1.1
>
> Tunnel adapter Teredo Tunneling Pseudo-Interface:
>
> Connection-specific DNS Suffix . :
> IP Address. . . . . . . . . . . . :
> 3ffe:831f:4004: 1956:0:fbde:bd0 a:e50b
> IP Address. . . . . . . . . . . . : fe80::5445:5245 :444f%5
> Default Gateway . . . . . . . . . : ::
>
> Tunnel adapter Automatic Tunneling Pseudo-Interface:
>
> Connection-specific DNS Suffix . :
> IP Address. . . . . . . . . . . . : fe80::5efe:192. 168.1.100%2
> Default Gateway . . . . . . . . . :
>
> E:\UserData\Den nis Lee Bieber\My Documents>
> **** END of captured output
> **** START of captured output
> dir
> Volume in drive E is Data
> Volume Serial Number is 2626-D991
>
> Directory of E:\UserData\Den nis Lee Bieber\My Documents
>
> 10/24/2005 09:23 AM <DIR>
> .
> 10/24/2005 09:23 AM <DIR>
> ..
> 07/25/2005 10:39 PM <DIR>
> .metadata
> 10/06/2005 09:54 AM <DIR>
> Ada Progs
> 08/13/2005 02:01 PM <DIR>
> Agent Data
> 10/21/2005 09:29 AM 421,820 apress_offer.pd f
> 07/03/2005 11:36 AM 132 cp.py
> 07/17/2005 12:25 PM <DIR>
> Cyberlink
> 07/06/2005 09:32 AM 102,400 db1.mdb
> 07/26/2005 12:20 AM 26,614 eclipse_code.xm l
> 10/24/2005 01:08 AM <DIR>
> Eudora
> 06/24/2005 08:50 PM 667 fake_oosums.ads
> 06/24/2005 08:50 PM 695 fake_oosums.ali
> 09/06/2005 09:01 PM <DIR>
> Genealogy
> 07/13/2005 10:56 PM <DIR>
> HomeSite
> 05/08/2005 01:05 PM <DIR>
> Investing
> 10/21/2005 10:04 PM <DIR>
> Java Progs
> 08/04/2005 10:13 PM 162 main.py
> 10/11/2005 10:43 PM <DIR>
> My Downloads
> 05/01/2005 10:31 AM <DIR>
> My eBooks
> 04/22/2005 12:09 AM <DIR>
> My Music
> 07/10/2005 11:43 AM <DIR>
> My Pictures
> 06/29/2005 11:55 PM <DIR>
> My PSP Files
> 05/23/2005 09:30 AM <DIR>
> My Videos
> 05/01/2005 12:49 PM <DIR>
> Office Documents
> 06/27/2005 03:19 PM 7,961,778
> org.eclipse.jdt .doc.user.I2005 0627-1435.pdf
> 06/27/2005 03:19 PM 6,791,109
> org.eclipse.pla tform.doc.user. I20050627-1435.pdf
> 10/11/2005 10:52 PM 56 oth_tsr_rm_750. ram
> 07/20/2005 09:32 AM 108,457 parkerred15yc.j pg
> 09/03/2005 10:36 PM <DIR>
> Python Progs
> 10/20/2005 10:38 PM <DIR>
> Quicken
> 07/10/2005 12:09 PM 3,356,248 results.xml
> 06/11/2005 12:03 PM 935 Scout_Ship Database.lnk
> 07/03/2005 12:38 PM <DIR>
> Scout_Ship My Documents
> 10/24/2005 09:23 AM 971 Script1.py
> 09/25/2005 12:40 PM 1,107 Script1_old.py
> 08/28/2005 11:47 AM <DIR>
> SimpleMu Logs
> 06/24/2005 08:56 PM 1,201 student_pack.ad s
> 06/24/2005 08:49 PM 1,144 student_pack.ad s.0
> 06/24/2005 08:56 PM 1,342 student_pack.al i
> 08/02/2005 11:39 PM 4,096 t.DOC
> 06/20/2005 10:11 AM 104 t.rx
> 08/05/2005 08:41 PM 66,452 Untitled-1.tif
> 08/05/2005 08:41 PM <DIR>
> VCheck
> 10/03/2005 02:58 AM <DIR>
> Visual Studio
> 10/03/2005 02:51 AM <DIR>
> Visual Studio 2005
> 21 File(s) 18,847,490 bytes
> 25 Dir(s) 267,162,845,184 bytes free
>
> E:\UserData\Den nis Lee Bieber\My Documents>
> **** END of captured output
>
> E:\UserData\Den nis Lee Bieber\My Documents>
>
> -=-=-=-=-=-=-=-=-
>
> Note that my "getLine()" has to return on either a real EOL, OR on
> the end of a command prompt ("stuff>"). I also had to initialize the
> prompt at the start. If someone issued a "cd" command to the subprocess,
> the prompt would be all out of sequence, and the code would hang.
>
> You'll also note that the prompt /ends/ a capture sequence, and the
> next command is the start of the /next/ capture sequence.
>
> --[color=green]
> > =============== =============== =============== =============== == <
> > wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> > wulfraed@dm.net | Bestiaria Support Staff <
> > =============== =============== =============== =============== == <
> > Home Page: <http://www.dm.net/~wulfraed/> <
> > Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color][/color]

[jas]

Re: Read/Write from/to a process

actually, i can't check for ">" only because if you a dir, a line can
end with a > but is not the end of the output

jas wrote:[color=blue]
> Thanks, that is certainly a start. As you mentioned, the "cd" could is
> an issue.
>
> Perhaps checking to see if the line ends with ">" is sufficient?
>
> Dennis Lee Bieber wrote:[color=green]
> > On 24 Oct 2005 07:20:42 -0700, "jas" <codecraig@gmai l.com> declaimed the
> > following in comp.lang.pytho n:
> >[color=darkred]
> > > Hi,
> > > I would like to start a new process and be able to read/write from/to
> > > it. I have tried things like...
> > >
> > > import subprocess as sp
> > > p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
> > > p.stdin.write(" hostname\n")
> > >
> > > however, it doesn't seem to work. I think the cmd.exe is catching it.[/color]
> >
> > One: you didn't read any of the "returned" output...
> >
> > Two: the output only seems to be available upon EOF, which means the
> > spawned command processor has to exit first... Though you CAN read one
> > character at a time, and then have to build lines and expected prompt
> > strings...
> >
> >
> > This seems to work:
> > -=-=-=-=-=-=-=-=-
> > import subprocess
> > import os
> >
> > PROMPT = os.getcwd() + ">"
> >
> > def getLine(proc):
> > ld = []
> > while True:
> > c = proc.stdout.rea d(1)
> > if c == "\r": continue #skip Windows <cr>
> > if c != "\n": ld.append(c) #save all but <lf>
> > if c is None or c == "\n" or c == ">": break
> > ln = "".join(ld)
> > return ln
> >
> > p = subprocess.Pope n("cmd.exe", stdout=subproce ss.PIPE, stdin =
> > subprocess.PIPE )
> >
> > print "**** START of captured output"
> > while True:
> > ln = getLine(p)
> > print ln
> > if ln == PROMPT: break
> > print "**** END of captured output"
> >
> > p.stdin.write(" ipconfig\n")
> > print "**** START of captured output"
> > while True:
> > ln = getLine(p)
> > print ln
> > if ln == PROMPT: break
> > print "**** END of captured output"
> >
> > p.stdin.write(" dir\n")
> > print "**** START of captured output"
> > while True:
> > ln = getLine(p)
> > print ln
> > if ln == PROMPT: break
> > print "**** END of captured output"
> >
> > p.stdin.write(" exit\n")
> > -=-=-=-=-=-=-=-=-=-
> > E:\UserData\Den nis Lee Bieber\My Documents>pytho n script1.py
> > **** START of captured output
> > Microsoft Windows XP [Version 5.1.2600]
> > (C) Copyright 1985-2001 Microsoft Corp.
> >
> > E:\UserData\Den nis Lee Bieber\My Documents>
> > **** END of captured output
> > **** START of captured output
> > ipconfig
> >
> > Windows IP Configuration
> >
> >
> > Ethernet adapter Local Area Connection:
> >
> > Connection-specific DNS Suffix . :
> > IP Address. . . . . . . . . . . . : 192.168.1.100
> > Subnet Mask . . . . . . . . . . . : 255.255.255.0
> > IP Address. . . . . . . . . . . . : fe80::211:11ff: fee1:f303%4
> > Default Gateway . . . . . . . . . : 192.168.1.1
> >
> > Tunnel adapter Teredo Tunneling Pseudo-Interface:
> >
> > Connection-specific DNS Suffix . :
> > IP Address. . . . . . . . . . . . :
> > 3ffe:831f:4004: 1956:0:fbde:bd0 a:e50b
> > IP Address. . . . . . . . . . . . : fe80::5445:5245 :444f%5
> > Default Gateway . . . . . . . . . : ::
> >
> > Tunnel adapter Automatic Tunneling Pseudo-Interface:
> >
> > Connection-specific DNS Suffix . :
> > IP Address. . . . . . . . . . . . : fe80::5efe:192. 168.1.100%2
> > Default Gateway . . . . . . . . . :
> >
> > E:\UserData\Den nis Lee Bieber\My Documents>
> > **** END of captured output
> > **** START of captured output
> > dir
> > Volume in drive E is Data
> > Volume Serial Number is 2626-D991
> >
> > Directory of E:\UserData\Den nis Lee Bieber\My Documents
> >
> > 10/24/2005 09:23 AM <DIR>
> > .
> > 10/24/2005 09:23 AM <DIR>
> > ..
> > 07/25/2005 10:39 PM <DIR>
> > .metadata
> > 10/06/2005 09:54 AM <DIR>
> > Ada Progs
> > 08/13/2005 02:01 PM <DIR>
> > Agent Data
> > 10/21/2005 09:29 AM 421,820 apress_offer.pd f
> > 07/03/2005 11:36 AM 132 cp.py
> > 07/17/2005 12:25 PM <DIR>
> > Cyberlink
> > 07/06/2005 09:32 AM 102,400 db1.mdb
> > 07/26/2005 12:20 AM 26,614 eclipse_code.xm l
> > 10/24/2005 01:08 AM <DIR>
> > Eudora
> > 06/24/2005 08:50 PM 667 fake_oosums.ads
> > 06/24/2005 08:50 PM 695 fake_oosums.ali
> > 09/06/2005 09:01 PM <DIR>
> > Genealogy
> > 07/13/2005 10:56 PM <DIR>
> > HomeSite
> > 05/08/2005 01:05 PM <DIR>
> > Investing
> > 10/21/2005 10:04 PM <DIR>
> > Java Progs
> > 08/04/2005 10:13 PM 162 main.py
> > 10/11/2005 10:43 PM <DIR>
> > My Downloads
> > 05/01/2005 10:31 AM <DIR>
> > My eBooks
> > 04/22/2005 12:09 AM <DIR>
> > My Music
> > 07/10/2005 11:43 AM <DIR>
> > My Pictures
> > 06/29/2005 11:55 PM <DIR>
> > My PSP Files
> > 05/23/2005 09:30 AM <DIR>
> > My Videos
> > 05/01/2005 12:49 PM <DIR>
> > Office Documents
> > 06/27/2005 03:19 PM 7,961,778
> > org.eclipse.jdt .doc.user.I2005 0627-1435.pdf
> > 06/27/2005 03:19 PM 6,791,109
> > org.eclipse.pla tform.doc.user. I20050627-1435.pdf
> > 10/11/2005 10:52 PM 56 oth_tsr_rm_750. ram
> > 07/20/2005 09:32 AM 108,457 parkerred15yc.j pg
> > 09/03/2005 10:36 PM <DIR>
> > Python Progs
> > 10/20/2005 10:38 PM <DIR>
> > Quicken
> > 07/10/2005 12:09 PM 3,356,248 results.xml
> > 06/11/2005 12:03 PM 935 Scout_Ship Database.lnk
> > 07/03/2005 12:38 PM <DIR>
> > Scout_Ship My Documents
> > 10/24/2005 09:23 AM 971 Script1.py
> > 09/25/2005 12:40 PM 1,107 Script1_old.py
> > 08/28/2005 11:47 AM <DIR>
> > SimpleMu Logs
> > 06/24/2005 08:56 PM 1,201 student_pack.ad s
> > 06/24/2005 08:49 PM 1,144 student_pack.ad s.0
> > 06/24/2005 08:56 PM 1,342 student_pack.al i
> > 08/02/2005 11:39 PM 4,096 t.DOC
> > 06/20/2005 10:11 AM 104 t.rx
> > 08/05/2005 08:41 PM 66,452 Untitled-1.tif
> > 08/05/2005 08:41 PM <DIR>
> > VCheck
> > 10/03/2005 02:58 AM <DIR>
> > Visual Studio
> > 10/03/2005 02:51 AM <DIR>
> > Visual Studio 2005
> > 21 File(s) 18,847,490 bytes
> > 25 Dir(s) 267,162,845,184 bytes free
> >
> > E:\UserData\Den nis Lee Bieber\My Documents>
> > **** END of captured output
> >
> > E:\UserData\Den nis Lee Bieber\My Documents>
> >
> > -=-=-=-=-=-=-=-=-
> >
> > Note that my "getLine()" has to return on either a real EOL, OR on
> > the end of a command prompt ("stuff>"). I also had to initialize the
> > prompt at the start. If someone issued a "cd" command to the subprocess,
> > the prompt would be all out of sequence, and the code would hang.
> >
> > You'll also note that the prompt /ends/ a capture sequence, and the
> > next command is the start of the /next/ capture sequence.
> >
> > --[color=darkred]
> > > =============== =============== =============== =============== == <
> > > wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> > > wulfraed@dm.net | Bestiaria Support Staff <
> > > =============== =============== =============== =============== == <
> > > Home Page: <http://www.dm.net/~wulfraed/> <
> > > Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color][/color][/color]

[jas]

Re: Read/Write from/to a process

What about having a thread which reads from subprocess.Pope n()'s
stdout...instea d of read/write, read/write. just always read, and
write when needed?

any comments on that idea?

jas wrote:[color=blue]
> actually, i can't check for ">" only because if you a dir, a line can
> end with a > but is not the end of the output
>
> jas wrote:[color=green]
> > Thanks, that is certainly a start. As you mentioned, the "cd" could is
> > an issue.
> >
> > Perhaps checking to see if the line ends with ">" is sufficient?
> >
> > Dennis Lee Bieber wrote:[color=darkred]
> > > On 24 Oct 2005 07:20:42 -0700, "jas" <codecraig@gmai l.com> declaimed the
> > > following in comp.lang.pytho n:
> > >
> > > > Hi,
> > > > I would like to start a new process and be able to read/write from/to
> > > > it. I have tried things like...
> > > >
> > > > import subprocess as sp
> > > > p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
> > > > p.stdin.write(" hostname\n")
> > > >
> > > > however, it doesn't seem to work. I think the cmd.exe is catching it.
> > >
> > > One: you didn't read any of the "returned" output...
> > >
> > > Two: the output only seems to be available upon EOF, which means the
> > > spawned command processor has to exit first... Though you CAN read one
> > > character at a time, and then have to build lines and expected prompt
> > > strings...
> > >
> > >
> > > This seems to work:
> > > -=-=-=-=-=-=-=-=-
> > > import subprocess
> > > import os
> > >
> > > PROMPT = os.getcwd() + ">"
> > >
> > > def getLine(proc):
> > > ld = []
> > > while True:
> > > c = proc.stdout.rea d(1)
> > > if c == "\r": continue #skip Windows <cr>
> > > if c != "\n": ld.append(c) #save all but <lf>
> > > if c is None or c == "\n" or c == ">": break
> > > ln = "".join(ld)
> > > return ln
> > >
> > > p = subprocess.Pope n("cmd.exe", stdout=subproce ss.PIPE, stdin =
> > > subprocess.PIPE )
> > >
> > > print "**** START of captured output"
> > > while True:
> > > ln = getLine(p)
> > > print ln
> > > if ln == PROMPT: break
> > > print "**** END of captured output"
> > >
> > > p.stdin.write(" ipconfig\n")
> > > print "**** START of captured output"
> > > while True:
> > > ln = getLine(p)
> > > print ln
> > > if ln == PROMPT: break
> > > print "**** END of captured output"
> > >
> > > p.stdin.write(" dir\n")
> > > print "**** START of captured output"
> > > while True:
> > > ln = getLine(p)
> > > print ln
> > > if ln == PROMPT: break
> > > print "**** END of captured output"
> > >
> > > p.stdin.write(" exit\n")
> > > -=-=-=-=-=-=-=-=-=-
> > > E:\UserData\Den nis Lee Bieber\My Documents>pytho n script1.py
> > > **** START of captured output
> > > Microsoft Windows XP [Version 5.1.2600]
> > > (C) Copyright 1985-2001 Microsoft Corp.
> > >
> > > E:\UserData\Den nis Lee Bieber\My Documents>
> > > **** END of captured output
> > > **** START of captured output
> > > ipconfig
> > >
> > > Windows IP Configuration
> > >
> > >
> > > Ethernet adapter Local Area Connection:
> > >
> > > Connection-specific DNS Suffix . :
> > > IP Address. . . . . . . . . . . . : 192.168.1.100
> > > Subnet Mask . . . . . . . . . . . : 255.255.255.0
> > > IP Address. . . . . . . . . . . . : fe80::211:11ff: fee1:f303%4
> > > Default Gateway . . . . . . . . . : 192.168.1.1
> > >
> > > Tunnel adapter Teredo Tunneling Pseudo-Interface:
> > >
> > > Connection-specific DNS Suffix . :
> > > IP Address. . . . . . . . . . . . :
> > > 3ffe:831f:4004: 1956:0:fbde:bd0 a:e50b
> > > IP Address. . . . . . . . . . . . : fe80::5445:5245 :444f%5
> > > Default Gateway . . . . . . . . . : ::
> > >
> > > Tunnel adapter Automatic Tunneling Pseudo-Interface:
> > >
> > > Connection-specific DNS Suffix . :
> > > IP Address. . . . . . . . . . . . : fe80::5efe:192. 168.1.100%2
> > > Default Gateway . . . . . . . . . :
> > >
> > > E:\UserData\Den nis Lee Bieber\My Documents>
> > > **** END of captured output
> > > **** START of captured output
> > > dir
> > > Volume in drive E is Data
> > > Volume Serial Number is 2626-D991
> > >
> > > Directory of E:\UserData\Den nis Lee Bieber\My Documents
> > >
> > > 10/24/2005 09:23 AM <DIR>
> > > .
> > > 10/24/2005 09:23 AM <DIR>
> > > ..
> > > 07/25/2005 10:39 PM <DIR>
> > > .metadata
> > > 10/06/2005 09:54 AM <DIR>
> > > Ada Progs
> > > 08/13/2005 02:01 PM <DIR>
> > > Agent Data
> > > 10/21/2005 09:29 AM 421,820 apress_offer.pd f
> > > 07/03/2005 11:36 AM 132 cp.py
> > > 07/17/2005 12:25 PM <DIR>
> > > Cyberlink
> > > 07/06/2005 09:32 AM 102,400 db1.mdb
> > > 07/26/2005 12:20 AM 26,614 eclipse_code.xm l
> > > 10/24/2005 01:08 AM <DIR>
> > > Eudora
> > > 06/24/2005 08:50 PM 667 fake_oosums.ads
> > > 06/24/2005 08:50 PM 695 fake_oosums.ali
> > > 09/06/2005 09:01 PM <DIR>
> > > Genealogy
> > > 07/13/2005 10:56 PM <DIR>
> > > HomeSite
> > > 05/08/2005 01:05 PM <DIR>
> > > Investing
> > > 10/21/2005 10:04 PM <DIR>
> > > Java Progs
> > > 08/04/2005 10:13 PM 162 main.py
> > > 10/11/2005 10:43 PM <DIR>
> > > My Downloads
> > > 05/01/2005 10:31 AM <DIR>
> > > My eBooks
> > > 04/22/2005 12:09 AM <DIR>
> > > My Music
> > > 07/10/2005 11:43 AM <DIR>
> > > My Pictures
> > > 06/29/2005 11:55 PM <DIR>
> > > My PSP Files
> > > 05/23/2005 09:30 AM <DIR>
> > > My Videos
> > > 05/01/2005 12:49 PM <DIR>
> > > Office Documents
> > > 06/27/2005 03:19 PM 7,961,778
> > > org.eclipse.jdt .doc.user.I2005 0627-1435.pdf
> > > 06/27/2005 03:19 PM 6,791,109
> > > org.eclipse.pla tform.doc.user. I20050627-1435.pdf
> > > 10/11/2005 10:52 PM 56 oth_tsr_rm_750. ram
> > > 07/20/2005 09:32 AM 108,457 parkerred15yc.j pg
> > > 09/03/2005 10:36 PM <DIR>
> > > Python Progs
> > > 10/20/2005 10:38 PM <DIR>
> > > Quicken
> > > 07/10/2005 12:09 PM 3,356,248 results.xml
> > > 06/11/2005 12:03 PM 935 Scout_Ship Database.lnk
> > > 07/03/2005 12:38 PM <DIR>
> > > Scout_Ship My Documents
> > > 10/24/2005 09:23 AM 971 Script1.py
> > > 09/25/2005 12:40 PM 1,107 Script1_old.py
> > > 08/28/2005 11:47 AM <DIR>
> > > SimpleMu Logs
> > > 06/24/2005 08:56 PM 1,201 student_pack.ad s
> > > 06/24/2005 08:49 PM 1,144 student_pack.ad s.0
> > > 06/24/2005 08:56 PM 1,342 student_pack.al i
> > > 08/02/2005 11:39 PM 4,096 t.DOC
> > > 06/20/2005 10:11 AM 104 t.rx
> > > 08/05/2005 08:41 PM 66,452 Untitled-1.tif
> > > 08/05/2005 08:41 PM <DIR>
> > > VCheck
> > > 10/03/2005 02:58 AM <DIR>
> > > Visual Studio
> > > 10/03/2005 02:51 AM <DIR>
> > > Visual Studio 2005
> > > 21 File(s) 18,847,490 bytes
> > > 25 Dir(s) 267,162,845,184 bytes free
> > >
> > > E:\UserData\Den nis Lee Bieber\My Documents>
> > > **** END of captured output
> > >
> > > E:\UserData\Den nis Lee Bieber\My Documents>
> > >
> > > -=-=-=-=-=-=-=-=-
> > >
> > > Note that my "getLine()" has to return on either a real EOL, OR on
> > > the end of a command prompt ("stuff>"). I also had to initialize the
> > > prompt at the start. If someone issued a "cd" command to the subprocess,
> > > the prompt would be all out of sequence, and the code would hang.
> > >
> > > You'll also note that the prompt /ends/ a capture sequence, and the
> > > next command is the start of the /next/ capture sequence.
> > >
> > > --
> > > > =============== =============== =============== =============== == <
> > > > wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> > > > wulfraed@dm.net | Bestiaria Support Staff <
> > > > =============== =============== =============== =============== == <
> > > > Home Page: <http://www.dm.net/~wulfraed/> <
> > > > Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color][/color][/color]

[Dennis Lee Bieber]

Re: Read/Write from/to a process

On 24 Oct 2005 10:17:39 -0700, "jas" <codecraig@gmai l.com> declaimed the
following in comp.lang.pytho n:
[color=blue]
> Thanks, that is certainly a start. As you mentioned, the "cd" could is
> an issue.
>
> Perhaps checking to see if the line ends with ">" is sufficient?[/color]

That would work IF you knew that was the end of the line. Look at my
code -- the > is being treated AS the signal for EOL because a prompt
from the system does NOT have a <cr><lf> sequence. (A more robust
version of the above would assume that if the text up to the > is NOT
the prompt, the line is not complete, read some more...)
--[color=blue]
> =============== =============== =============== =============== == <
> wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> =============== =============== =============== =============== == <
> Home Page: <http://www.dm.net/~wulfraed/> <
> Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color]

[Dennis Lee Bieber]

Re: Read/Write from/to a process

On 24 Oct 2005 10:38:43 -0700, "jas" <codecraig@gmai l.com> declaimed the
following in comp.lang.pytho n:
[color=blue]
> What about having a thread which reads from subprocess.Pope n()'s
> stdout...instea d of read/write, read/write. just always read, and
> write when needed?
>[/color]
Regardless of how you do it, you still have to have a means of
detecting when the subprocess has stopped for input (IE, it is at a
prompt which did not supply a <cr><lf> sequence). Unfortunately, on
Windows, the select() function only works with sockets, and not files,
or you could do a simple select with time-out... Say one second... If no
read data is available after one second assume a system prompt is
present.

You might want to see if http://pexpect.sourceforge.net/ has
anything of use... Whoops -- no... Doesn't work on base Windows...



{And PLEASE trim your replies -- there is a reason top-posting is
frowned upon, besides the fact that people coming in cold end up reading
stuff in the reverse order: top-posting is like Jeopardy, one sees the
answer and then has to figure out the question... But the other reason
is that top-posting software tends to propagate meaningless quotes
because the quote is below, and ignored by the top-poster when making
comment... You made three responses and quoted my couple of hundred
lines each time, yet the only relevant substance was the paragraph about
detecting EOL or prompt}
--[color=blue]
> =============== =============== =============== =============== == <
> wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> =============== =============== =============== =============== == <
> Home Page: <http://www.dm.net/~wulfraed/> <
> Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color]

[jas]

Re: Read/Write from/to a process

So it seems there is no good way to handle "interactiv e" processes on
windows using python. By interactive I mean processes/commands that
require user interaction, such as telnet or del (to delete a file or
directory sometimes you need to confirm with a yes or no), date, etc.

os.system gives the exact behavior, but you can't redirec the output.
pexpect isn't supported on windows. Even with subprocess you can't
handle all/most cases..since you have to do things like look for he
prompt.

I modified the original suggestion so it would update the prompt, in
case the user did a "cd.." ..which works fine now. However, if a user
tries to do, "del tmp123" ...windows prompts for a "are you sure you
want to delete... Y/N?" ...so the code hangs.

I can't believe no one else has done this yet..or if they have, it
hasn't been widely discussed.

Any other suggestions?

[Steve Holden]

Re: Read/Write from/to a process

jas wrote:[color=blue]
> So it seems there is no good way to handle "interactiv e" processes on
> windows using python. By interactive I mean processes/commands that
> require user interaction, such as telnet or del (to delete a file or
> directory sometimes you need to confirm with a yes or no), date, etc.
>
> os.system gives the exact behavior, but you can't redirec the output.
> pexpect isn't supported on windows. Even with subprocess you can't
> handle all/most cases..since you have to do things like look for he
> prompt.
>
> I modified the original suggestion so it would update the prompt, in
> case the user did a "cd.." ..which works fine now. However, if a user
> tries to do, "del tmp123" ...windows prompts for a "are you sure you
> want to delete... Y/N?" ...so the code hangs.
>
> I can't believe no one else has done this yet..or if they have, it
> hasn't been widely discussed.
>
> Any other suggestions?
>[/color]
Look at how you might do it in other languages. Then you'll realise this
isn't (just) a Python problem.

regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/

[jas]

Re: Read/Write from/to a process

Steve Holden wrote:[color=blue]
> Look at how you might do it in other languages. Then you'll realise this
> isn't (just) a Python problem.[/color]

Yea your right. However, for example, in Java, one can use the Process
class, and then read from the stream until its the end (i.e. -1 is
returned). However, with Python when reading from
subprocess.Pope n.stdout ...I don't know when to stop (except for
looking for a ">" or something). Is there a standard, like read until
"-1" or something?

As I mentioned, os.system("cmd" ) gives me exactly the
output/interactivity I need...but I can't redirect the output.

Thanks.

[Michael Schneider]

Re: Read/Write from/to a process

Jas,

I use a python called twisted to run processes as you describe.

Twisted is an event-driven framework that brings a change in the
way that you look at things.

take a look at:

http://twistedmatrix.com/projects/core/documentation/howto/process.html

Good luck, hope this is useful,
Mike


jas wrote:[color=blue]
> Hi,
> I would like to start a new process and be able to read/write from/to
> it. I have tried things like...
>
> import subprocess as sp
> p = sp.Popen("cmd.e xe", stdout=sp.PIPE)
> p.stdin.write(" hostname\n")
>
> however, it doesn't seem to work. I think the cmd.exe is catching it.
>
> I also tried
> f = open("out.txt", "w")
> sys.stdout = f
> os.system("cmd. exe")
>
> ..but out.txt didn't contain any output from cmd.exe
>
> So, how can I create a process (in this case, cmd.exe) on Windows and
> be able to read/write from/to it?
>
> Thanks
>[/color]


--
The greatest performance improvement occurs on the transition of from
the non-working state to the working state.

[Donn Cave]

Re: Read/Write from/to a process

Quoth "jas" <codecraig@gmai l.com>:
| Steve Holden wrote:
|> Look at how you might do it in other languages. Then you'll realise this
|> isn't (just) a Python problem.
|
| Yea your right. However, for example, in Java, one can use the Process
| class, and then read from the stream until its the end (i.e. -1 is
| returned). However, with Python when reading from
| subprocess.Pope n.stdout ...I don't know when to stop (except for
| looking for a ">" or something). Is there a standard, like read until
| "-1" or something?

Sure, end of file is '', a string with 0 bytes. That means the other
end of the pipe has closed, usually due to exit of the other process
that was writing to it. Not much help for you there, nor would the
Java equivalent be, I presume.

Even on UNIX, where pipes are a mainstay of ordinary applications,
this one would very likely need a pseudotty device instead, to prevent
C library block buffering, and it would still be difficult and unreliable.

Ironically the best support I've seen came from a platform that didn't
use pipes much at all, VAX/VMS (I put that in the past tense because
for all I know it may have evolved in this respect.) The pipe-like
VMS device was called a "mailbox", and the interesting feature was
that you could be notified when a read had been queued on the device.

Donn Cave, donn@drizzle.co m

[Dennis Lee Bieber]

Re: Read/Write from/to a process

On 25 Oct 2005 05:22:20 -0700, "jas" <codecraig@gmai l.com> declaimed the
following in comp.lang.pytho n:
[color=blue]
> So it seems there is no good way to handle "interactiv e" processes on
> windows using python. By interactive I mean processes/commands that
> require user interaction, such as telnet or del (to delete a file or
> directory sometimes you need to confirm with a yes or no), date, etc.
>[/color]
telnetlib includes an "expect" method...
[color=blue]
> os.system gives the exact behavior, but you can't redirec the output.
> pexpect isn't supported on windows. Even with subprocess you can't
> handle all/most cases..since you have to do things like look for he
> prompt.[/color]

That applies to any OS... If you have no IPC signalling mechanism
that the other process has completed an output phase and is now waiting
for input, you must scan for whatever is the "current" prompt. Even an
"expect" module is "expecting" to find something you had to specify in
advance.

Heck... How do YOU recognize that an application running in a
command window is waiting for input?

I suspect you do it by reading the output text and recognizing that
the cursor is on a line that looks like a prompt. The main difference is
that you have cognitive understanding of what IS the prompt, and can
recognize the differences between, say an [abort, retry, exit] prompt
and c:\junk> prompt. To programmaticall y handle this situation, you have
to code the logic to recognize the two possible prompts.
[color=blue]
>
> I modified the original suggestion so it would update the prompt, in
> case the user did a "cd.." ..which works fine now. However, if a user
> tries to do, "del tmp123" ...windows prompts for a "are you sure you
> want to delete... Y/N?" ...so the code hangs.
>
> I can't believe no one else has done this yet..or if they have, it
> hasn't been widely discussed.
>
> Any other suggestions?[/color]

Don't try to do a pass-through of everything to a command
interpreter -- instead write your own command interpreter IN Python.

Parse "cd ..." => os.chdir("...")
"del ..." => os.remove("..." )

etc.

Basically, any command that can change the environment should be
handled by your program, not a pass through. But of course, if you then
try to handle an external interactive program, you'd have to know what
it uses for prompts.

The other possibility (and I have a dental appointment to get to so
can't spend another hour trying to code it) is to, yes, use a thread to
fetch characters one at a time from the subprocess output. Use a Queue
to pass those characters to another thread for assembly into "lines" (on
a <cr> or <lf> you have an obvious line -- pass it on to the main
processing thread). The Queue process will need to loop until the queue
has been empty for some defined amount of time -- this delay with no
data would be the signal that a prompt message likely has been received,
and any "incomplete " line would be returned to the main process along
with a flag saying "prompt" [pity select() can't be used, or you could
combine the Queue processing and read-1-char thread into a single
thread]
--[color=blue]
> =============== =============== =============== =============== == <
> wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> =============== =============== =============== =============== == <
> Home Page: <http://www.dm.net/~wulfraed/> <
> Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color]

[Dennis Lee Bieber]

Re: Read/Write from/to a process

On Tue, 25 Oct 2005 15:29:12 -0000, "Donn Cave" <donn@drizzle.c om>
declaimed the following in comp.lang.pytho n:
[color=blue]
> Ironically the best support I've seen came from a platform that didn't
> use pipes much at all, VAX/VMS (I put that in the past tense because
> for all I know it may have evolved in this respect.) The pipe-like
> VMS device was called a "mailbox", and the interesting feature was
> that you could be notified when a read had been queued on the device.
>[/color]
Followed by the Amiga... The Amiga IPC used "message ports" (linked
lists owned by the creating process to which, if "public" [named], other
processes could send message packets). The Amiga port of REXX made use
of message ports as its native IPC...

address SOME_APPLICATIO N

would redirect all "non-REXX" statements to the message port named
"SOME_APPLICATI ON"; the default being "address COMMAND" -- a shell
interpreter. Then, any non-REXX statement would be processed by the
shell interpreter -- and the easiest way to force a non-REXX statement
was to put a quote mark around it (or the first word of it)

"delete" my_file_var

would translate my_file_var to whatever had been assigned to it earlier,
and pass a delete command to the shell.

address ED

would now route such statements to the "ed" editor

No explicit "write" needed to send stuff to the subprocess.
--[color=blue]
> =============== =============== =============== =============== == <
> wlfraed@ix.netc om.com | Wulfraed Dennis Lee Bieber KD6MOG <
> wulfraed@dm.net | Bestiaria Support Staff <
> =============== =============== =============== =============== == <
> Home Page: <http://www.dm.net/~wulfraed/> <
> Overflow Page: <http://wlfraed.home.ne tcom.com/> <[/color]

[jas]

Re: Read/Write from/to a process

I have setup multiple threads and a queue...which is working pretty
good. But I have one other issue...I have a new thread (since it is
different issue) here:

http://groups.google.com/group/comp.lang.python/browse_frm/thread/ec81d8982d1a0130

if you get chance, would you mind checking that out.

Thanks!