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• Python - store output of subprocess() call in a string

  - by Mark

  Hey all, I'm trying to make a system call in Python and store the output to a string that I can manipulate in the Python program. #!/usr/bin/python import subprocess p = subprocess.Popen("pwd") # edit - actual command I want to store output of p2 = subprocess.Popen("ntpq -p") I've tried a few things including some of the suggestions here: http://stackoverflow.com/questions/1996518/retrieving-the-output-of-subprocess-call but without any luck. Many thanks!

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• Why does output of fltk-config truncate arguments to gcc?

  - by James Morris

  I'm trying to build an application I've downloaded which uses the SCONS "make replacement" and the Fast Light Tool Kit Gui. The SConstruct code to detect the presence of fltk is: guienv = Environment(CPPFLAGS = '') guiconf = Configure(guienv) if not guiconf.CheckLibWithHeader('lo', 'lo/lo.h','c'): print 'Did not find liblo for OSC, exiting!' Exit(1) if not guiconf.CheckLibWithHeader('fltk', 'FL/Fl.H','c++'): print 'Did not find FLTK for the gui, exiting!' Exit(1) Unfortunately, on my (Gentoo Linux) system, and many others (Linux distributions) this can be quite troublesome if the package manager allows the simultaneous install of FLTK-1 and FLTK-2. I have attempted to modify the SConstruct file to use fltk-config --cflags and fltk-config --ldflags (or fltk-config --libs might be better than ldflags) by adding them like so: guienv.Append(CPPPATH = os.popen('fltk-config --cflags').read()) guienv.Append(LIBPATH = os.popen('fltk-config --ldflags').read()) But this causes the test for liblo to fail! Looking in config.log shows how it failed: scons: Configure: Checking for C library lo... gcc -o .sconf_temp/conftest_4.o -c "-I/usr/include/fltk-1.1 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_THREAD_SAFE -D_REENTRANT" gcc: no input files scons: Configure: no How should this really be done? And to complete my answer, how do I remove the quotes from the result of os.popen( 'command').read()? EDIT The real question here is why does appending the output of fltk-config cause gcc to not receive the filename argument it is supposed to compile?

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• Graceful DOS Command Error-Handling

  - by Captain Obvious

  PHP 5.2.13 on Windows 2003 I am using the DOS Start /B command to launch a background application using the PHP popen() function: popen("start /B {$_SERVER['HOMEPATH']}/{$app}.exe > {$_SERVER['HOMEPATH']}/bg_output.log 2>&1 & echo $!", 'r'); The popen() function launches a cmd.exe process that runs the specified command; however, if the command fails (e.g. the {$app}.exe doesn't exist or is locked in the above example), the cmd.exe process never returns, and PHP hangs indefinitely as a result. Calling the failing DOS command directly using the Command Prompt results in an Error prompt that requires clicking the OK button. I assume this error confirmation requirement is what's preventing the cmd.exe process from returning to PHP both from the Command Prompt (using both CGI and CLI) and the web (using Apache 2.0 handler w/Apache 2.2). Is there a way to write the DOS command or configure the server or cmd.exe app itself to return the DOS error to the originating call rather than waiting for confirmation?

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• Secure Copy File from remote server via scp and os module in Python

  - by user1063572

  I'm pretty new to Python and programming. I'm trying to copy a file between two computers via a python script. However the code os.system("ssh " + hostname + " scp " + filepath + " " + user + "@" + localhost + ":" cwd) won't work. I think it needs a password, as descriped in How do I copy a file to a remote server in python using scp or ssh?. I didn't get any error logs, the file just won't show in my current working directory. However every other command with os.system("ssh " + hostname + "command") or os.popen("ssh " + hostname + "command") does work. - command = e.g. ls When I try ssh hostname scp file user@local:directory in the commandline it works without entering a password. I tried to combine os.popen commands with getpass and pxssh module to establish a ssh connection to the remote server and use it to send commands directly (I only tested it for an easy command): import pxssh import getpass ssh = pxssh.pxssh() ssh.force_password = True hostname = raw_input("Hostname: ") user = raw_input("Username: ") password = getpass.getpass("Password: ") ssh.login(hostname, user, password) test = os.popen("hostname") print test But I'm not able to put commands through to the remote server (print test shows, that hostname = local and not the remote server), however I'm sure, the conection is established. I thought it would be easier to establish a connection than always use "ssh " + hostname in the bash commands. I also tried some of the workarounds in How do I copy a file to a remote server in python using scp or ssh?, but I must admit due to lack of expirience I didn't get them to work. Thanks a lot for helping me.

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• Python: Check existence of shell command before execution

  - by Gabriel L. Oliveira

  Hi all. I'm trying to find a way to check the existence of a shell command before its execution. For example, I'll execute the command ack-grep. So, I'm trying to do: import subprocess from subprocess import PIPE cmd_grep = subprocess.Popen(["ack-grep", "--no-color", "--max-count=1", "--no-group", "def run_main", "../cgedit/"], stdout=PIPE, stderr=PIPE) Than, if I execute cmd_grep.stderr.read() I receive '' like the output. But I don't have the command ack-grep on my path. So, why Popen is not putting the error message on my .stderr variable? Also, is there a easyer way to do what I'm trying to do?

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• Reproduce PIPE functionality in IronPython

  - by Muppet Geoff

  Hi, I am hoping some genious out there can help me out with this... I am using sox to merge and resample a group of WAV files, and pipe the output directly to the input of NeroAACEnc for encoding to AAC format. I originally ran the process in a script, which included: sox.exe d:\audio\1.wav d:\audio\2.wav d:\audio\3.wav -c 1 -r 22050 -t wav - | neroAacEnc.exe -q 0.5 -if - -of test.m4a This worked as expected. The '-' in the comand line translates as 'Pipe/redirect input/output (stdin/stdout)' - So Sox pipes to stdout, and NeroAACEnc reads from stdin, the | joins them together. I then migrated the whole solution to Python, and the equivalent command became: from subprocess import call, Popen, PIPE runwav = Popen(['sox.exe', 'd:\audio\1.wav', 'd:\audio\2.wav', 'd:\audio\3.wav', '-c', '1', '-r', '22050', '-t', 'wav', '-'], shell=False, stdout=PIPE) runm4b = call(['neroAacEnc.exe', '-q', '0.5', '-if', '-', '-of', 'test.m4a'], shell=False, stdin=runwav.stdout) This also worked like a charm, exactly as expected. Slightly more convoluted, but hey :) Well now I have to move it to IronPython, and the Subprocess module isn't available (the partial implementation that is, doesn't have Popen/PIPE support - plus it seems silly to add a custom library when there is probably a native alternative). I should mention here, that I opted for IronPython over C#, because I am comfortable with Python now - however, there is a chance of moving it again later to C# native, and I am using IronPython to ease myself into it :) I have no C# or .net experience. So far I have the following equivalent, that sets up the 2 processes: from System.Diagnostics import Process wav = Process() wav.StartInfo.UseShellExecute = False wav.StartInfo.RedirectStandardOutput = True wav.StartInfo.FileName = 'sox.exe' wav.StartInfo.Arguments = 'd:\audio\1.wav d:\audio\2.wav d:\audio\3.wav -c 1 -r 22050 -t wav -' wav.Start() m4b = Process() m4b.StartInfo.UseShellExecute = False m4b.StartInfo.RedirectStandardInput = True m4b.StartInfo.FileName = 'neroAacEnc.exe' m4b.StartInfo.Arguments = '-q 0.5 -if - -of test.m4a' m4b.Start() I know that these 2 processes start (I can see Nero and Sox in the task manager) but what I can't figure out (for the life of me) is how to string the two output/input streams together, as with the previous two solutions. I have searched and searched, so I thought I'd ask! If anyone knows either: How to join the two streams with the same net result as the Python and Commandline versions; or A better way to acheive what I am trying to do. I would be extremely grateful! Many thanks in advance, Geoff P.S. A code sample based off the above would be awesome :) or a specific code example of a similar process that I can easily translate... this has broked my brayne.

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• Launching python within python and timezone issue

  - by Gabi Purcaru

  I had to make a launcher script for my django app, and it seems it somehow switches the timezone to GMT (default being +2), and every datetime is two hours behind when using the script. What could be causing that? Here is the launcher script that I use: #!/usr/bin/env python import os import subprocess import shlex import time cwd = os.getcwd() p1 = subprocess.Popen(shlex.split("python manage.py runserver"), cwd=os.path.join(cwd, "drugsworld")) p2 = subprocess.Popen(shlex.split("python coffee_auto_compiler.py"), cwd=os.path.join(cwd)) try: while True: time.sleep(2) except KeyboardInterrupt: p1.terminate() p2.terminate() If I manually run python manage.py runserver, the timezone is +2. If, however, I use this script, the timezone is set to GMT.

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• Cleaning up temp folder after long-running subprocess exits

  - by dbr

  I have a Python script (running inside another application) which generates a bunch of temporary images. I then use subprocess to launch an application to view these. When the image-viewing process exists, I want to remove the temporary images. I can't do this from Python, as the Python process may have exited before the subprocess completes. I.e I cannot do the following: p = subprocess.Popen(["imgviewer", "/example/image1.jpg", "/example/image1.jpg"]) p.communicate() os.unlink("/example/image1.jpg") os.unlink("/example/image2.jpg") ..as this blocks the main thread, nor could I check for the pid exiting in a thread etc The only solution I can think of means I have to use shell=True, which I would rather avoid: cmd = ['imgviewer'] cmd.append("/example/image2.jpg") for x in cleanup: cmd.extend(["&&", "rm", x]) cmdstr = " ".join(cmd) subprocess.Popen(cmdstr, shell = True) This works, but is hardly elegant, and will fail with filenames containing spaces etc.. Basically, I have a background subprocess, and want to remove the temp files when it exits, even if the Python process no longer exists.

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• Looping an executable to get the result from Python script

  - by fx

  In my python script, I need to call within a for loop an executable, and waiting for that executable to write the result on the "output.xml". How do I manage to use wait() & how do I know when one of my executable is finished generating the result to get the result? How do I close that process and open a new one to call again the executable and wait for the new result? import subprocess args = ("bin/bar") popen = subprocess.Popen(args) I need to wait for the output from "bin/bar" to generate the "output.xml" and from there, read it's content. for index, result in enumerate(results): myModule.callSubProcess(index) #this is where the problem is. fileOutput = open("output.xml") parseAndStoreInSQLiteFileOutput(index, file)

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• Python 3 - Module: subprocess

  - by Rhys

  Hi Stack Overflow users, I've encountered a frustrating problem, can't find the answer to it. Yesterday I was trying to find a way to HIDE a subprocess.Popen. So for example, if i was opening the cmd. I would like it to be hidden, permanently. I found this code: kwargs = {} if subprocess.mswindows: su = subprocess.STARTUPINFO() su.dwFlags |= subprocess.STARTF_USESHOWWINDOW su.wShowWindow = subprocess.SW_HIDE kwargs['startupinfo'] = su subprocess.Popen("cmd.exe", **kwargs) It worked like a charm! But today, for reasons I don't need to get into, I had to reinstall python 3 (32bit) Now, when I run my program I get this error: Traceback (most recent call last): File "C:\Python31\hello.py", line 7, in <module> su.dwFlags |= subprocess.STARTF_USESHOWWINDOW AttributeError: 'module' object has no attribute 'STARTF_USESHOWWINDOW' I'm using 32bit, python3.1.3 ... just like before. If you have any clues/alternatives PLEASE post, thanks. NOTE: I am looking for a SHORT method to hide the app, not like two pages of code please

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• Executing python subprocess via git hook

  - by aljesco

  I'm running Gitolite over the Git repository and I have post-receive hook there written in Python. I need to execute "git" command at git repository directory. There are few lines of code: proc = subprocess.Popen(['git', 'log', '-n1'], cwd='/home/git/repos/testing.git' stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc.communicate() After I make new commit and push to repository, scripts executes and says fatal: Not a git repository: '.' If I run proc = subprocess.Popen(['pwd'], cwd='/home/git/repos/testing.git' stdout=subprocess.PIPE, stderr=subprocess.PIPE) it says, as expected, correct path to git repository (/home/git/repos/testing.git) If I run this script manually from bash, it works correct and show correct output of "git log". What I'm doing wrong?

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• How do I redirect stdin/stdout when I have a sequence of commands in Bash?

  - by Tom

  I've currently got a Bash command being executed (via Python's subprocess::Popen) which is reading from stdin, doing something and outputing to stdout. Something along the lines of: pid = subprocess.Popen( ["-c", "cmd1 | cmd2"], stdin = subprocess.PIPE, stdout = subprocess.PIPE, shell =True ) output_data = pid.communicate( "input data\n" ) Now, what I want to do is to change that to execute another command in that same subshell that will alter the state before the next commands execute, so my shell command line will now (conceptually) be: cmd0; cmd1 | cmd2 Is there any way to have the input sent to cmd1 instead of cmd0 in this scenario? I'm assuming the output will include cmd0's output (which will be empty) followed by cmd2's output. cmd0 shouldn't actually read anything from stdin, does that make a difference in this situation? I know this is probably just a dumb way of doing this, I'm trying to patch in cmd0 without altering the other code too significantly. That said, I'm open to suggestions if there's a much cleaner way to approach this.

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• Uptime under linux in C

  - by drizzt

  Hi, How can I retrieve uptime under linux using C? (without using popen and/or /proc) Thanks

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• Using pipes inside a class in C++

  - by Paul

  I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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• Multiple calls to /dev/stdin using python subprocess (*nix)

  - by Alex Leach

  Hi, I have a python subprocess call which I would like to link up to three pipes (two standard in and one standard out). I know that there is only one /dev/stdin, but there's all those other devices in /dev I don't know about, and don't know of any python os, sys or subprocess modules that will utilise them in a manner which allows me to give the device path to subprocess.Popen. The reason I ask is because I would like to pipe information from a mysql database or tar archive rather than a directory structure I currently have which has 28,000 directories in. The directory names alone uses a LOT of space! The alternative is to tar / gunzip the entire directory structure and manoeuvre through the compressed archive. With either solution, mysql or tar, I would still like to have two pipes into subprocess.Popen and one out, so that I can bypass the HDD. Any need for an example??

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• start /B doesn't start the task

  - by Fractaliste

  I'm currently launching an asynchronous job with PHP to perform some tests. To make it work, I found on SO some tips, like the use of popen and start: $commande = "testu.bat"; $pid = popen('start /B ' . $commande, 'r'); $status = pclose($pid); The testu.bat's folder is in my user PATH. This script performs some task, and to control it's execution, it should generates a log file, but I never get it. Whereas if I just remove the /B option, it works fine and I get my log file. Did I miss something about background execution? How can I catch the error informations when it is running in the background?

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• communicate with a process in utf-8 on a cp1252 consoless

  - by Mapad

  I need to control a program by sending commands in utf-8 encoding to its standard input. For this I run the program using subprocess.Popen(): proc = Popen("myexecutable.exe", shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE) proc.stdin.write(u'ééé'.encode('utf_8')) If I run this from a cygwin utf-8 console, it works. If I run it from a windows console (encoding ='cp1252') this doesn't work. Is there a way to make this work without having to install a cygwin utf-8 console on each computer I want it to run from ? (NB: I don't need to output anything to console)

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• Run command with no terminal output

  - by Insomaniacal

  Hello, I've searched around online, but can't find the answer to my question. What I want to do is run a command in pythong, using the subprocess module, and store the output in a variable. However, I do not want the command's output to be printed to the terminal. For this code: def storels(): a = subprocess.Popen("ls",shell=True) storels() I get the directory listing in the terminal, instead of having it stored in a. I've also tried def storels(): subprocess.Popen("ls > tmp",shell=True) a = open("./tmp") [Rest of Code] storels() This also prints the output of ls to my terminal. I've even tried this command with the somewhat dated os.system method, since running "ls tmp" in the terminal doesn't print ls to the terminal at all, but stores it in tmp. However, the same thing happens. I'm using python 2.6. Any suggestions? Thanks in advance!

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• Why does Alacarte give me this error when I try to add items to the menu?

  - by RichardoC

  When I try to add anything to the menu in 12.04 I get this error. $ alacarte Traceback (most recent call last): File "/usr/share/alacarte/Alacarte/MainWindow.py", line 317, in on_new_item_button_clicked process = subprocess.Popen(['gnome-desktop-item-edit', file_path], env=os.environ) File "/usr/lib/python2.7/subprocess.py", line 679, in __init__ errread, errwrite) File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child raise child_exception OSError: [Errno 2] No such file or directory Thank you, R.C.

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• How to control gnome-terminal from Python scrypt?

  - by user936401

  I am developing an application in PyGtk, and would like to launch a gnome-terminal and output commands to it. My user should then be able to modify the command, or maybe ignore using the up arrow ... etc. I have been able to launch a terminal, but can't work out how to send commands. This is how my application starts: class App(Gtk.Window): def __init__(self): Gtk.Window.__init__(self) process=subprocess.Popen(["gnome-terminal", "--class=App", "--name=app"], shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE) response,error=process.communicate()

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• Comparing 2 (or 3 Files If Possible) "Line By Line"

  - by PythEch

  I want to find out the differences of 2 (or 3 files if possible) line by line. Diff utils can do this, however it gives inaccurate results. Because, 2 files have exact number of lines which is "134". But diff gives me "Added Lines" and "Removed Lines". However this is wrong, they have exact the same number of lines, there is no added or removed lines. The text files which I want to find differences of them, have only numbers written, maybe that's why that algortihm fails. I couldn't find any option to prevent that, however I may be wrong, I mean there should be an option for that, but again, I couldn't find. This is what I get (5am.txt vs 6am.txt, there is a huge problem): This is what I want (6am.txt vs 7am.txt, still has problems): But, first the first image still has this problem, at the last lines. Edit: After I figured out that there is no utility to do this, I handled myself. I almost did the same thing as what RedGrittyBrick have done. This script imitates diff utility so I (or you) can use it with diff2html. To use it with diff2html, just change line diff_stdout = os.popen("diff %s" % string.join(argv[1:]), "r") to diff_stdout = os.popen("script.py %s" % string.join(argv[1:]), "r") and name this script whatever you want: import sys f1=open(sys.argv[1],"r") f1_read=f1.readlines() f1.close() f2=open(sys.argv[2],"r") f2_read=f2.readlines() f2.close() changed={} first_c = "" for n in range(len(f1_read)): if f1_read[n]!=f2_read[n]: if first_c == "": first_c=n+1 changed[first_c]=n+1 else: first_c="" #Let's imitate diff-utils... for (x, y) in changed.items(): print "%d,%dc%d,%d" % (x,y,x,y) for i in range(x,y+1): sys.stdout.write("< %s" % f1_read[i-1]) print "---" for i in range(x,y+1): sys.stdout.write("> %s" % f2_read[i-1]) Final results:

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• Dealing with external processes

  - by Jesse Aldridge

  I've been working on a gui app that needs to manage external processes. Working with external processes leads to a lot of issues that can make a programmer's life difficult. I feel like maintenence on this app is taking an unacceptably long time. I've been trying to list the things that make working with external processes difficult so that I can come up with ways of mitigating the pain. This kind of turned into a rant which I thought I'd post here in order to get some feedback and to provide some guidance to anybody thinking about sailing into these very murky waters. Here's what I've got so far: Output from the child can get mixed up with output from the parent. This can make both outputs misleading and hard to read. It can be hard to tell what came from where. It becomes harder to figure out what's going on when things are asynchronous. Here's a contrived example: import textwrap, os, time from subprocess import Popen test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) proc = Popen('python -B "%s"' % test_path) for i in range(3): print 'Hello %i' % i time.sleep(1) os.remove(test_path) I guess I could have the child process write its output to a file. But it can be annoying to have to open up a file every time I want to see the result of a print statement. If I have code for the child process I could add a label, something like print 'child: Hello %i', but it can be annoying to do that for every print. And it adds some noise to the output. And of course I can't do it if I don't have access to the code. I could manually manage the process output. But then you open up a huge can of worms with threads and polling and stuff like that. A simple solution is to treat processes like synchronous functions, that is, no further code executes until the process completes. In other words, make the process block. But that doesn't work if you're building a gui app. Which brings me to the next problem... Blocking processes cause the gui to become unresponsive. import textwrap, sys, os from subprocess import Popen from PyQt4.QtGui import * from PyQt4.QtCore import * test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) app = QApplication(sys.argv) button = QPushButton('Launch process') def launch_proc(): # Can't move the window until process completes proc = Popen('python -B "%s"' % test_path) proc.communicate() button.connect(button, SIGNAL('clicked()'), launch_proc) button.show() app.exec_() os.remove(test_path) Qt provides a process wrapper of its own called QProcess which can help with this. You can connect functions to signals to capture output relatively easily. This is what I'm currently using. But I'm finding that all these signals behave suspiciously like goto statements and can lead to spaghetti code. I think I want to get sort-of blocking behavior by having the 'finished' signal from QProcess call a function containing all the code that comes after the process call. I think that should work but I'm still a bit fuzzy on the details... Stack traces get interrupted when you go from the child process back to the parent process. If a normal function screws up, you get a nice complete stack trace with filenames and line numbers. If a subprocess screws up, you'll be lucky if you get any output at all. You end up having to do a lot more detective work everytime something goes wrong. Speaking of which, output has a way of disappearing when dealing external processes. Like if you run something via the windows 'cmd' command, the console will pop up, execute the code, and then disappear before you have a chance to see the output. You have to pass the /k flag to make it stick around. Similar issues seem to crop up all the time. I suppose both problems 3 and 4 have the same root cause: no exception handling. Exception handling is meant to be used with functions, it doesn't work with processes. Maybe there's some way to get something like exception handling for processes? I guess that's what stderr is for? But dealing with two different streams can be annoying in itself. Maybe I should look into this more... Processes can hang and stick around in the background without you realizing it. So you end up yelling at your computer cuz it's going so slow until you finally bring up your task manager and see 30 instances of the same process hanging out in the background. Also, hanging background processes can interefere with other instances of the process in various fun ways, such as causing permissions errors by holding a handle to a file or someting like that. It seems like an easy solution to this would be to have the parent process kill the child process on exit if the child process didn't close itself. But if the parent process crashes, cleanup code might not get called and the child can be left hanging. Also, if the parent waits for the child to complete, and the child is in an infinite loop or something, you can end up with two hanging processes. This problem can tie in to problem 2 for extra fun, causing your gui to stop responding entirely and force you to kill everything with the task manager. F***ing quotes Parameters often need to be passed to processes. This is a headache in itself. Especially if you're dealing with file paths. Say... 'C:/My Documents/whatever/'. If you don't have quotes, the string will often be split at the space and interpreted as two arguments. If you need nested quotes you can use ' and ". But if you need to use more than two layers of quotes, you have to do some nasty escaping, for example: "cmd /k 'python \'path 1\' \'path 2\''". A good solution to this problem is passing parameters as a list rather than as a single string. Subprocess allows you to do this. Can't easily return data from a subprocess. You can use stdout of course. But what if you want to throw a print in there for debugging purposes? That's gonna screw up the parent if it's expecting output formatted a certain way. In functions you can print one string and return another and everything works just fine. Obscure command-line flags and a crappy terminal based help system. These are problems I often run into when using os level apps. Like the /k flag I mentioned, for holding a cmd window open, who's idea was that? Unix apps don't tend to be much friendlier in this regard. Hopefully you can use google or StackOverflow to find the answer you need. But if not, you've got a lot of boring reading and frusterating trial and error to do. External factors. This one's kind of fuzzy. But when you leave the relatively sheltered harbor of your own scripts to deal with external processes you find yourself having to deal with the "outside world" to a much greater extent. And that's a scary place. All sorts of things can go wrong. Just to give a random example: the cwd in which a process is run can modify it's behavior. There are probably other issues, but those are the ones I've written down so far. Any other snags you'd like to add? Any suggestions for dealing with these problems?

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• How to replace openSSL calls with C# code?

  - by fonix232

  Hey there again! Today I ran into a problem when I was making a new theme creator for chrome. As you may know, Chrome uses a "new" file format, called CRX, to manage it's plugins and themes. It is a basic zip file, but a bit modified: "Cr24" + derkey + signature + zipFile And here comes the problem. There are only two CRX creators, written in Ruby or Python. I don't know neither language too much (had some basic experience in Python though, but mostly with PyS60), so I would like to ask you to help me convert this python app to a C# code that doesn't depend on external programs. Also, here is the source of crxmake.py: #!/usr/bin/python # Cribbed from http://github.com/Constellation/crxmake/blob/master/lib/crxmake.rb # and http://src.chromium.org/viewvc/chrome/trunk/src/chrome/tools/extensions/chromium_extension.py?revision=14872&content-type=text/plain&pathrev=14872 # from: http://grack.com/blog/2009/11/09/packing-chrome-extensions-in-python/ import sys from array import * from subprocess import * import os import tempfile def main(argv): arg0,dir,key,output = argv # zip up the directory input = dir + ".zip" if not os.path.exists(input): os.system("cd %(dir)s; zip -r ../%(input)s . -x '.svn/*'" % locals()) else: print "'%s' already exists using it" % input # Sign the zip file with the private key in PEM format signature = Popen(["openssl", "sha1", "-sign", key, input], stdout=PIPE).stdout.read(); # Convert the PEM key to DER (and extract the public form) for inclusion in the CRX header derkey = Popen(["openssl", "rsa", "-pubout", "-inform", "PEM", "-outform", "DER", "-in", key], stdout=PIPE).stdout.read(); out=open(output, "wb"); out.write("Cr24") # Extension file magic number header = array("l"); header.append(2); # Version 2 header.append(len(derkey)); header.append(len(signature)); header.tofile(out); out.write(derkey) out.write(signature) out.write(open(input).read()) os.unlink(input) print "Done." if __name__ == '__main__': main(sys.argv) Please could you help me?

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• Mercurial 1.5 pager on Windows

  - by alexandrul

  I'm trying to set the pager used for Mercurial but the output is empty, even if I specify the command in the [pager] section or as the PAGER environment variable. I noticed that the command provided is launched with cmd.exe. Is this the cause of empty output, and if yes, what is the right syntax? Environment: Mercurial 1.5, Mecurial 1.4.3 hgrc: [extensions] pager = [pager] pager = d:\tools\less\less.exe Sample command lines (from Process Explorer): hg diff c:\windows\system32\cmd.exe /c "d:\tools\less\less.exe 2> NUL:" d:\tools\less\less.exe UPDATE In pager.py, by replacing: sys.stderr = sys.stdout = util.popen(p, "wb") with sys.stderr = sys.stdout = subprocess.Popen(p, stdin = subprocess.PIPE, shell=False).stdin I managed to obtain the desired output for the hg status and diff. BUT, I'm sure it's wrong (or at least incomplete), and I have no control over the pager app (less.exe): the output is shown in the cmd.exe window, I can see the less prompt (:) but any further input is fed into cmd.exe. It seems that the pager app is still active in the background: after typing exit in the cmd.exe window, I have control over the pager app, and I can terminate it normally. Also, it makes no difference what I'm choosing as a pager app (more is behaving the same). UPDATE 2 Issue1677 - [PATCH] pager for "hg help" output on windows

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• eventmachine and external scripts via backticks

  - by Maciek

  I have a small HTTP server script I've written using eventmachine which needs to call external scripts/commands and does so via backticks (``). When serving up requests which don't run backticked code, everything is fine, however, as soon as my EM code executes any backticked external script, it stops serving requests and stops executing in general. I noticed eventmachine seems to be sensitive to sub-processes and/or threads, and appears to have the popen method for this purpose, but EM's source warns that this method doesn't work under Windows. Many of the machines running this script are running Windows, so I can't use popen. Am I out of luck here? Is there a safe way to run an external command from an eventmachine script under Windows? Is there any way I could fire off some commands to be run externally without blocking EM's execution? edit: the culprit that seems to be screwing up EM the most is my usage of the Windows start command, as in: start java myclass. The reason I'm using start is because I want those external scripts to start running and keep running after the EM request is served

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