If you want to write the output to a file you can use the [stdout][1]-argument of `subprocess.call`.

It takes either

- `None` (the default, stdout is inherited from the parent (your script))
- `subprocess.PIPE` (allows you to pipe from one command/process to another)
- a file object or a file descriptor (what you want, to have the output written to a file)

You need to open a file with something like `open` and pass the object or file descriptor integer to `call`:

    f = open(&quot;blah.txt&quot;, &quot;w&quot;)
    subprocess.call([&quot;/home/myuser/run.sh&quot;, &quot;/tmp/ad_xml&quot;,  &quot;/tmp/video_xml&quot;], stdout=f)

I&#39;m guessing any valid file-like object would work, like a socket (gasp :)), but I&#39;ve never tried.

As [marcog][2] mentions in the comments you might want to redirect stderr as well, you can redirect this to the same location as stdout with `stderr=subprocess.STDOUT`. Any of the above mentioned values works as well, you can redirect to different places.


  [1]: http://docs.python.org/library/subprocess.html#subprocess.Popen
  [2]: https://stackoverflow.com/users/89806/marcog

The options for `popen` can be used in `call`


    args, 
    bufsize=0, 
    executable=None, 
    stdin=None, 
    stdout=None, 
    stderr=None, 
    preexec_fn=None, 
    close_fds=False, 
    shell=False, 
    cwd=None, 
    env=None, 
    universal_newlines=False, 
    startupinfo=None, 
    creationflags=0

So... 

    myoutput = open(&#39;somefile.txt&#39;, &#39;w&#39;)
    subprocess.call([&quot;/home/myuser/run.sh&quot;, &quot;/tmp/ad_xml&quot;,  &quot;/tmp/video_xml&quot;], stdout=myoutput)

Then you can do what you want with `myoutput`

Also, you can do something closer to a piped output like this.


    dmesg | grep hda
    
would be:    

    p1 = Popen([&quot;dmesg&quot;], stdout=PIPE)
    p2 = Popen([&quot;grep&quot;, &quot;hda&quot;], stdin=p1.stdout, stdout=PIPE)
    output = p2.communicate()[0]

There&#39;s plenty of lovely, useful info on the [python manual page][1].


  [1]: http://docs.python.org/library/subprocess.html#subprocess.Popen

I&#39;m using Linq To XML

    new XElement(&quot;Prefix&quot;, Prefix == null ? &quot;&quot; : Prefix)

but I want to do some computation to the prefix before adding it to the xml, like eliminating spaces, special chars, some calculations etc 

I don&#39;t want to create functions because this ones won&#39;t be of any help on any other part of my program but this, so is there any way to create inline functions??

How to make inline functions in C#

I am wondering if this is possible at all. I want to update column x if a condition is true, otherwise column y would be updated

    UPDATE table SET
         (CASE (CONDITION) WHEN TRUE THEN columnx
                           ELSE columny
          END)
    = 25
I have searched all over, tried out some things and am unable to find a solution. I think it&#39;s not possible, but I thought I would ask here and see if anyone has done it before. Thanks in advance.

T-SQL: Using a CASE in an UPDATE statement to update certain columns depending on a condition

    subprocess.call([&quot;/home/myuser/run.sh&quot;, &quot;/tmp/ad_xml&quot;,  &quot;/tmp/video_xml&quot;])

RIght now I have a script that I run. When I run it and it hits this line, it starts printing stuff because run.sh has prints in it.

How do I pipe this to a text file also? (And also print, if possible)

How do I pipe a subprocess call to a text file?

<pre><code class="hljs language-css">subprocess.call(["/home/myuser/run.sh", "/tmp/ad_xml", "/tmp/video_xml"])
</code></pre>
RIght now I have a script that I run. When I run it and it hits this line, it starts printing stuff because run.sh has prints in it.
How do I pipe this to a text file also? (And also print, if possible)

Is there a javascript equivalent of Python&#39;s zip function?  That is, given multiple arrays of equal lengths create an array of pairs.

For instance, if I have three arrays that look like this:

    var array1 = [1, 2, 3];
    var array2 = [&#39;a&#39;,&#39;b&#39;,&#39;c&#39;];
    var array3 = [4, 5, 6];

The output array should be:

    var output array:[[1,&#39;a&#39;,4], [2,&#39;b&#39;,5], [3,&#39;c&#39;,6]]




Javascript equivalent of Python&#39;s zip function

    from numpy import *
    def swap_columns(my_array, col1, col2):
        temp = my_array[:,col1]
        my_array[:,col1] = my_array[:,col2]
        my_array[:,col2] = temp

Then

    swap_columns(data, 0, 1)

Doesn&#39;t work. However, calling the code directly

    temp = my_array[:,0]
    my_array[:,0] = my_array[:,1]
    my_array[:,1] = temp

Does. Why is this happening and how can I fix it? The Error says &quot;IndexError: 0-d arrays can only use a single () or a list of newaxes (and a single ...) as an index&quot;, which implies the arguments aren&#39;t ints? I already tried converting the cols to int but that didn&#39;t solve it.

Swapping columns in a numpy array?

How to enumerate all imported modules?

E.g. I would like to get `[&#39;os&#39;, &#39;sys&#39;]` from this code:

    import os
    import sys


How to list imported modules?

The question I&#39;m about to ask seems to be a duplicate of https://stackoverflow.com/questions/674304/pythons-use-of-new-and-init, but regardless, it&#39;s still unclear to me exactly what the practical difference between `__new__` and `__init__` is.

Before you rush to tell me that `__new__` is for creating objects and `__init__` is for initializing objects, let me be clear: **I get that.**  In fact, that distinction is quite natural to me, since I have experience in C++ where we have [placement new][1], which similarly separates object allocation from initialization.  

The [Python C API tutorial][2] explains it like this:

&gt; The new member is responsible for
&gt; creating (as opposed to initializing)
&gt; objects of the type. It is exposed in
&gt; Python as the `__new__()` method. ...
&gt; **One reason to implement a new method is to assure the initial values of
&gt; instance variables**.

So, yeah - I *get* what `__new__` does, but despite this, I *still* don&#39;t understand why it&#39;s useful in Python.  The example given says that `__new__` might be useful if you want to &quot;assure the initial values of instance variables&quot;. Well, isn&#39;t that exactly what `__init__` will do?  

In the C API tutorial, an example is shown where a new Type (called a &quot;Noddy&quot;) is created, and the Type&#39;s `__new__` function is defined.  The Noddy type contains a string member called `first`, and this string member is initialized to an empty string like so:

    static PyObject * Noddy_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
    {
        .....
    
        self-&gt;first = PyString_FromString(&quot;&quot;);
        if (self-&gt;first == NULL)
        {
           Py_DECREF(self);
           return NULL;
        }
    
        .....
    }

Note that without the `__new__` method defined here, we&#39;d have to use `PyType_GenericNew`, which simply initializes all of the instance variable members to NULL.  So the only benefit of the `__new__` method is that the instance variable will start out as an empty string, as opposed to NULL.  **But why is this ever useful, since if we cared about making sure our instance variables are initialized to some default value, we could have just done that in the `__init__` method?** 



  [1]: https://stackoverflow.com/questions/222557/cs-placement-new
  [2]: http://docs.python.org/release/3.0.1/extending/newtypes.html


Python (and Python C API): __new__ versus __init__

How can I get a random pair from a `dict`? I&#39;m making a game where you need to guess a capital of a country and I need questions to appear randomly.

The `dict` looks like `{&#39;VENEZUELA&#39;:&#39;CARACAS&#39;}`

How can I do this?

How to get a random value from dictionary?

I need to configure a server with a few files and I want to do it programmatically.

I need to create files say  `/home/a.config, /var/spool/b.config, /etc/c.config`

Files above have some contents (multi lines).

I want to create ONE shell script which can create all three file with multiple lines (around 10).
I would like to know the how can I use `CAT` command to do that. (inside shell script).

I am looking something like this


    echo &quot; going to create  /home/a.config&quot;
    
    cat &quot;HOW CAN I HAVE MULTIPLE LINES HERE?? &quot; &gt;  /home/a.config 

thanks



Creating files with some content with shell script

I need to add a cron job thru a script I run to set up a server. I am currently using Ubuntu. I can use `crontab -e` but that will open an editor to edit the current crontab. I want to do this programmatically.

Is it possible to do so?

How do I create a crontab through a script

So, I&#39;m sure I&#39;m missing something simple here, but when I run mongo as a daemon (using mongod --fork or just mongod), I see different database content than if I just run &quot;mongo&quot; on the host machine.

My only assumption is that the data is being stored somewhere other than /data/db when it&#39;s running just the shell, and switches to /data/db when I boot the mongod. In that case, how do I get at my data when running mongod?

Mongodb - Difference between running &quot;mongo&quot; and &quot;mongod&quot; databases

I am using bash shell on linux and want to use more than 10 parameters in shell script


How to handle more than 10 parameters in shell

I&#39;m looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.

I&#39;ve managed to do it with the telnet command, and it works fine when the port is opened, but it doesn&#39;t seem to timeout when it&#39;s not and just hangs there...

Here&#39;s a sample:

    l_TELNET=`echo &quot;quit&quot; | telnet $SERVER $PORT | grep &quot;Escape character is&quot;`
    if [ &quot;$?&quot; -ne 0 ]; then
      echo &quot;Connection to $SERVER on port $PORT failed&quot;
      exit 1
    else
      echo &quot;Connection to $SERVER on port $PORT succeeded&quot;
      exit 0
    fi


I either need a better way, or a way to force telnet to timeout if it doesn&#39;t connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).

I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.

Note: This is what my server is running (where I need to run this from)

SunOS 5.10 Generic_139556-08 i86pc i386 i86pc

Test if remote TCP port is open from a shell script

What I do in the command line:

    cat file1 file2 file3 &gt; myfile

What I want to do with python:

    import subprocess, shlex
    my_cmd = &#39;cat file1 file2 file3 &gt; myfile&#39;
    args = shlex.split(my_cmd)
    subprocess.call(args) # spits the output in the window i call my python program

How to redirect output with subprocess in Python?

How do I retrieve the exit code when using Python&#39;s `subprocess` module and the `communicate()` method?

Relevant code:

    import subprocess as sp
    data = sp.Popen(openRTSP + opts.split(), stdout=sp.PIPE).communicate()[0]

Should I be doing this another way?

How to get exit code when using Python subprocess communicate method?

Suppose there&#39;s an executable and a Python script to launch it, and they&#39;re located in &#39;sibling&#39; subdirectories, e.g.

    /tmp/subdir1/myexecutable
    /tmp/subdir2/myscript.py

If in `/tmp` and running `python subdir2/myscript.py` with a relative path to executable

    # myscript.py
    from subprocess import Popen
    proc = Popen([&quot;../subdir1/myexecutable&quot;])

It makes `OSError: [Errno 2] No such file or directory`.

How does the Python search for the executable? Does it use the current working directory and/or location of the script? Does it use PATH and/or PYTHONPATH? Can you change where and how `subprocess.Popen` searches for the executable? Are commands, absolute and relative paths for executables treated differently? Are there differences between Linux and Windows? What does `shell=True` or `shell=False` influence?


python subprocess Popen environment PATH?

I&#39;m wondering if this is the correct way to execute a system process and detach from parent, though allowing the parent to exit without creating a zombie and/or killing the child process.  I&#39;m currently using the subprocess module and doing this...

    os.setsid() 
    os.umask(0) 
    p = subprocess.Popen([&#39;nc&#39;, &#39;-l&#39;, &#39;8888&#39;],
                         cwd=self.home,
                         stdout=subprocess.PIPE, 
                         stderr=subprocess.STDOUT)

os.setsid() changes the process group, which I believe is what lets the process continue running when it&#39;s parent exits, as it no longer belongs to the same process group.

Is this correct and also is this a reliable way of performing this?

Basically, I have a remote control utility that communicate through sockets and allows to start processes remotely, but I have to ensure that if the remote control dies, the processes it started continue running unaffected.

I was reading about double-forks and not sure if this is necessary and/or subprocess.POpen close_fds somehow takes care of that and all that&#39;s needed is to change the process group?

Thanks.

Ilya

Python spawn off a child subprocess, detach, and exit

I want to get the output from some shell commands like `ls` or `df` in a python script. I see that `commands.getoutput(&#39;ls&#39;)` is deprecated but `subprocess.call(&#39;ls&#39;)` will only get me the return code.

I&#39;ll hope there is some simple solution.

Content Type	Original Author	Original Content on Stackoverflow
Question	TIMEX	View Question on Stackoverflow
Solution 1 - Python	Skurmedel	View Answer on Stackoverflow
Solution 2 - Python	ocodo	View Answer on Stackoverflow

How do I pipe a subprocess call to a text file?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

T-SQL: Using a CASE in an UPDATE statement to update certain columns depending on a condition

How to make inline functions in C#

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