Re: Python without a tty
hello, On Mon, Oct 03, 2011 at 04:37:43AM +, Steven D'Aprano wrote: I wanted to ensure that it would do the right thing when run without a tty, such as from a cron job. If you fork() your process, then it will also loose the tty... import os import sys try: pid = os.fork() if pid 0: sys.exit(0) except OSError, e: sys.exit(1) os.chdir(/) os.setsid() os.umask(0) a. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 3/10/11 08:10:57, Hegedüs, Ervin wrote: hello, On Mon, Oct 03, 2011 at 04:37:43AM +, Steven D'Aprano wrote: I wanted to ensure that it would do the right thing when run without a tty, such as from a cron job. If you fork() your process, then it will also loose the tty... Errhm, I suggest you check again. This cannot be true. import os import sys try: pid = os.fork() if pid 0: sys.exit(0) except OSError, e: sys.exit(1) os.chdir(/) os.setsid() os.umask(0) It is os.setsid() that makes you lose the tty. Hope this helps, -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
hello, On Mon, Oct 03, 2011 at 09:28:27AM +0200, Hans Mulder wrote: On 3/10/11 08:10:57, Hegedüs, Ervin wrote: If you fork() your process, then it will also loose the tty... Errhm, I suggest you check again. This cannot be true. os.setsid() It is os.setsid() that makes you lose the tty. well, thank you, I confused Python fork() and glibc daemon() - as I know that detach the terminal - I'm really sorry. a. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
Hegedüs wrote: If you fork() your process, then it will also loose the tty... Um, no, fork() doesn't do that, as far as I know. os.setsid() *This* is what's losing the tty. According to the Fine Man Page: DESCRIPTION The setsid function creates a new session. The calling process is the session leader of the new session, is the process group leader of a new process group and has no controlling terminal. ^^^ -- Greg -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On Mon, 03 Oct 2011 22:04:26 +1300, Gregory Ewing wrote: os.setsid() *This* is what's losing the tty. According to the Fine Man Page: DESCRIPTION The setsid function creates a new session. The calling process is the session leader of the new session, is the process group leader of a new process group and has no controlling terminal. ^^^ The above description is incomplete. This version has more detail: DESCRIPTION setsid() creates a new session if the calling process is not a process group leader. The calling process is the leader of the new session, the process group leader of the new process group, and has no control- ling tty. The process group ID and session ID of the calling process are set to the PID of the calling process. The calling process will be the only process in this new process group and in this new session. The key point is ... if the calling process is not a process group leader. The easiest way to achieve this condition is to fork(). This ensures that the child process won't be a process group leader unless it explicitly makes itself one with setpgid() or setpgrp(). A process launched from a shell typically /will/ be a process group leader unless it's part of a pipeline (the shell creates a new process group for each pipeline; one of the processes in that group will be its leader). setsid() will fail with EPERM if the calling process is a process group leader. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On Fri, 30 Sep 2011 21:09:54 +0100, Nobody wrote: On Thu, 29 Sep 2011 11:53:12 +0200, Alain Ketterlin wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? [...] I suspect that the OP just wants e.g.: script.py /dev/null - which will redirect stdout and stderr to /dev/null and close stdin. No, that's not what I wanted. I ended up just running the script as a cron job. It was a one-off (well, twice actually, since the first time demonstrated a bug in my code) test of some code that tries to determine the size of the current terminal. I wanted to ensure that it would do the right thing when run without a tty, such as from a cron job. Thanks to everyone who replied. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 3/10/11 06:37:43, Steven D'Aprano wrote: On Fri, 30 Sep 2011 21:09:54 +0100, Nobody wrote: On Thu, 29 Sep 2011 11:53:12 +0200, Alain Ketterlin wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? [...] I suspect that the OP just wants e.g.: script.py/dev/null- which will redirect stdout and stderr to /dev/null and close stdin. No, that's not what I wanted. I ended up just running the script as a cron job. It was a one-off (well, twice actually, since the first time demonstrated a bug in my code) test of some code that tries to determine the size of the current terminal. I wanted to ensure that it would do the right thing when run without a tty, such as from a cron job. In that case, the at command would have been the answer. It is a bit like cron, but meant for one-off jobs. You might have received more useful answers if you'd mentioned you goals earlier. -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On Sep 29, 3:52 am, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: Alain Ketterlin wrote: Steven D'Aprano steve+comp.lang.pyt...@pearwood.info writes: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. Isn't os.setsid() what you're looking for? It makes the calling process have no controlling terminal. There's also a user command called setsid that should have the same effect. It doesn't appear so to me. [steve@sylar ~]$ tty /dev/pts/16 [steve@sylar ~]$ setsid tty /dev/pts/16 [steve@sylar ~]$ python -c import sys,os; print os.isatty(sys.stdout.fileno()) True [steve@sylar ~]$ setsid python -c import sys,os; print os.isatty(sys.stdout.fileno()) True If I run the same Python command (without the setsid) as a cron job, I get False emailed to me. That's the effect I'm looking for. -- Steven You could try the old UNIX nohup ... technique for running a process in the background (the ) with no HangUP if you log out: $ nohup python -c import sys,os; print os.isatty(sys.stdout.fileno()) appending output to nohup.out $ cat nohup.out False But that is over kill I guess. One worrying detail the definition of a running process in UNIX implies is that it has standard input/output files open. You'd be wise to make sure that they are connected to things that are safe /dev/null. Even so /dev/tty can be opened any way... Hope this helps. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On Thu, 29 Sep 2011 11:53:12 +0200, Alain Ketterlin wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. Isn't os.setsid() what you're looking for? It makes the calling process have no controlling terminal. There's also a user command called setsid that should have the same effect. setsid() requires that the calling process isn't a process group leader; this can be achieved by fork()ing. The setsid command does this automatically. As you say, this ensures that the process has no controlling terminal (i.e. it won't get signals from the tty driver for ^C, ^Z, hangup, etc). It won't detach stdin etc from a terminal. Also, open()ing a tty will result in it becoming the controlling terminal unless O_NOCTTY is used. I suspect that the OP just wants e.g.: script.py /dev/null - which will redirect stdout and stderr to /dev/null and close stdin. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 30/09/11 20:34:37, RJB wrote: You could try the old UNIX nohup ... technique for running a process in the background (the) with no HangUP if you log out: $ nohup python -c import sys,os; print os.isatty(sys.stdout.fileno()) appending output to nohup.out $ cat nohup.out False But that is over kill I guess. One worrying detail the definition of a running process in UNIX implies is that it has standard input/output files open. You'd be wise to make sure that they are connected to things that are safe /dev/null. Even so /dev/tty can be opened any way... Not if you really detach from your tty: after you've detached, there is no tty for /dev/tty to connect to and any attempt to open it will raise IOError. -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Python without a tty
I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 29/09/11 11:21, Steven D'Aprano wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. ./program /dev/null /dev/null 21 -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info writes: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. Isn't os.setsid() what you're looking for? It makes the calling process have no controlling terminal. There's also a user command called setsid that should have the same effect. -- Alain. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
Alain Ketterlin wrote: Steven D'Aprano steve+comp.lang.pyt...@pearwood.info writes: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. Isn't os.setsid() what you're looking for? It makes the calling process have no controlling terminal. There's also a user command called setsid that should have the same effect. It doesn't appear so to me. [steve@sylar ~]$ tty /dev/pts/16 [steve@sylar ~]$ setsid tty /dev/pts/16 [steve@sylar ~]$ python -c import sys,os; print os.isatty(sys.stdout.fileno()) True [steve@sylar ~]$ setsid python -c import sys,os; print os.isatty(sys.stdout.fileno()) True If I run the same Python command (without the setsid) as a cron job, I get False emailed to me. That's the effect I'm looking for. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 29/09/11 11:21:16, Steven D'Aprano wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? There is module on Pypi called python-daemon; it implements PEP-3143. This module detaches the process from the tty and resets a number of process attributes that are normally inherited. You could start by reading the PEP to determine which of its features are relevant to your situation. It would provide you with a complete list of aspects you'd need to think about. If a third of what the module does is relevant to your situation and the other two thirds do not hurt, then using the module is likely to be less work than rolling your own. Hope this helps, -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 29/09/11 12:52:22, Steven D'Aprano wrote: [steve@sylar ~]$ python -c import sys,os; print os.isatty(sys.stdout.fileno()) True If I run the same Python command (without the setsid) as a cron job, I get False emailed to me. That's the effect I'm looking for. In that case, all you need to do is redirect stdout: $ python -c import sys, os print os.isatty(sys.stdout.fileno()) /tmp/xxx $ cat /tmp/xxx False You'll probably want to redirect to /dev/null and maybe you want to redirect stdin and stderr as well. -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info writes: Alain Ketterlin wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? Isn't os.setsid() what you're looking for?[...] It doesn't appear so to me. [...] [steve@sylar ~]$ python -c import sys,os; print os.isatty(sys.stdout.fileno()) True [steve@sylar ~]$ setsid python -c import sys,os; print os.isatty(sys.stdout.fileno()) True If I run the same Python command (without the setsid) as a cron job, I get False emailed to me. That's the effect I'm looking for. If that's what you mean by without a tty attached, simply redirecting standard channels should work, no? -- Alain. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info writes: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. You could crib from the ‘python-daemon’ library implementation URL:http://pypi.python.org/pypi/python-daemon. Part of its job involves detaching the current program from the terminal. Or maybe you could simply invoke the library for its main purpose, if that would be sufficient to do what you need. -- \“Sane people have an appropriate perspective on the relative | `\ importance of foodstuffs and human beings. Crazy people can't | _o__) tell the difference.” —Paul Z. Myers, 2010-04-18 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
In article 4e84388c$0$29965$c3e8da3$54964...@news.astraweb.com, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I'm not sure what you mean by without a tty attached to the process. If you mean no file descriptors attached to your control terminal, then some variation on foo.py /dev/null /dev/null (as others has suggested) might be good enough. Or, are you talking about control terminals in the process control sense? In that case, you might want to look at the at or batch commands, which do very much the same thing as cron, but without the overhead of having to edit the cron file to get things going. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On 29/09/2011 10:21, Steven D'Aprano wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. Well you could double fork and drop the parent, that would lose the tty which is the same effect what you get when you want a daemon. -- mph -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
It doesn't appear so to me. [steve@sylar ~]$ tty /dev/pts/16 [steve@sylar ~]$ setsid tty /dev/pts/16 [steve@sylar ~]$ python -c import sys,os; print os.isatty(sys.stdout.fileno()) True [steve@sylar ~]$ setsid python -c import sys,os; print os.isatty(sys.stdout.fileno()) True If I run the same Python command (without the setsid) as a cron job, I get False emailed to me. That's the effect I'm looking for. Maybe nohup is what you looking for? From the info pages... `nohup' runs the given COMMAND with hangup signals ignored, so that the command can continue running in the background after you log out. Synopsis: nohup COMMAND [ARG]... If standard output is a terminal, it is redirected so that it is appended to the file `nohup.out'; if that cannot be written to, it is appended to the file `$HOME/nohup.out'. If that cannot be written to, the command is not run. If standard output is not a terminal, then the standard output of COMMAND will be the same as that of `nohup'. Regards Bradley -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
On Sep 29, 5:21 am, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? I am running Linux. -- Steven Have you tried GNU Screen? It let's you run processes under virtual terminals, which can then be backgrounded, reconnected to, etc. I think it comes with most linux distros. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python without a tty
ron vacor...@gmail.com writes: On Sep 29, 5:21 am, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: I have a Python script which I would like to test without a tty attached to the process. I could run it as a cron job, but is there an easier way? Have you tried GNU Screen? It let's you run processes under virtual terminals, which can then be backgrounded, reconnected to, etc. I think it comes with most linux distros. That would not satisfy the “without a TTY attached” requirement. GNU Screen's main goal is to *provide* an attached TTY to multiple processes when the TTY isn't interacting with the user. I don't know whether Screen can *remove* a TTY from a process, and it would be strange to me if it did so. -- \ “I have yet to see any problem, however complicated, which, | `\ when you looked at it in the right way, did not become still | _o__)more complicated.” —Paul Anderson | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
