What will this command do? 

    exec 2&gt;&amp;1 

sh command: exec 2&gt;&amp;1

It looks like you can&#39;t use exec in a function that has a subfunction...

Anyone know why this Python code doesn&#39;t work?  I get an error at the exec in test2.  Also, I know exec&#39;s aren&#39;t good style, but trust me, I&#39;m using exec for an appropriate reason. I wouldn&#39;t use it otherwise.

    #!/usr/bin/env python
    #
    
    def test1():
        exec(&#39;print &quot;hi from test1&quot;&#39;)
    
    test1()
    
    def test2():
        &quot;&quot;&quot;Test with a subfunction.&quot;&quot;&quot;
        exec(&#39;print &quot;hi from test2&quot;&#39;)
        def subfunction():
            return True
    
    test2()

EDIT: I narrowed down the bug to having a function in a subfunction. It has nothing to do with the raise keyword.

Why doesn&#39;t exec work in a function with a subfunction?

Can a Java application be loaded in a separate process using its name, as opposed to its location, in a platform independent manner?

I know you can execute a program via ...

    Process process = Runtime.getRuntime().exec( COMMAND );

... the main issue of this method is that such calls are then platform specific.

&lt;br&gt;
Ideally, I&#39;d wrap a method into something as simple as...

    EXECUTE.application( CLASS_TO_BE_EXECUTED );

... and pass in the fully qualified name of an application class as `CLASS_TO_BE_EXECUTED`.


Executing a Java application in a separate process

I have spent the last 2 days trying to understand the `execlp()` system call, but yet here I am. Let me get straight to the issue.

The `man page` of execlp declares the system call as `int execlp(const char *file, const char *arg, ...);` with the description: *The const char arg and subsequent ellipses in the execl(), execlp(), and execle() functions can be thought of as arg0, arg1, ..., argn.*

Yet I see the system call being called like this in our text book: `execlp(“/bin/sh”, ..., “ls -l /bin/??”, ...);` (the &quot;...&quot; are for us to figure out as students). However this system call doesn&#180;t even resemble anything like the declaration on the `man page` of the system call.

I am super confused. Any help is appreciated.

I do not understand how execlp() works in Linux

I need to generate code for a method at runtime. It&#39;s important to be able to run arbitrary code and have a docstring.

I came up with a solution combining `exec` and `setattr`, here&#39;s a dummy example:

    class Viking(object):
        def __init__(self):
            code = &#39;&#39;&#39;
                def dynamo(self, arg):
                    &quot;&quot;&quot; dynamo&#39;s a dynamic method!
                    &quot;&quot;&quot;
                    self.weight += 1
                    return arg * self.weight
                &#39;&#39;&#39;
            self.weight = 50
            
            d = {}
            exec code.strip() in d
            setattr(self.__class__, &#39;dynamo&#39;, d[&#39;dynamo&#39;])
    
    
    if __name__ == &quot;__main__&quot;:
        v = Viking()
        print v.dynamo(10)
        print v.dynamo(10)
        print v.dynamo.__doc__
        
Is there a better / safer / more idiomatic way of achieving the same result?



Dynamic/runtime method creation (code generation) in Python

Is there a way to check in a php script if `exec()` is enabled or disabled on a server?

PHP exec - check if enabled or disabled

Can anyone explain what are the uses of the exec command in shell scripting with simple examples?

What are the uses of the exec command in shell scripts?

I was helped out today with a command, but it doesn&#39;t seem to be working. This is the command:

    find /home/me/download/ -type f -name &quot;*.rm&quot; -exec ffmpeg -i {} -sameq {}.mp3 &amp;&amp; rm {}\;

The shell returns

    find: missing argument to `-exec&#39;

What I am basically trying to do is go through a directory recursively (if it has other directories) and run the ffmpeg command on the `.rm` file types and convert them to `.mp3` file types. Once this is done, remove the `.rm` file that has just been converted.

I appreciate any help on this.

find: missing argument to -exec

I was looking to find the difference between these four on Google and I expected there to be a huge amount of information on this, but there really wasn&#39;t any solid comparison between the four calls. 

I set about trying to compile a kind of basic at-a-glance look at the differences between these system calls and here&#39;s what I got. Is all this information correct/am I missing anything important ?

`Fork` : The fork call basically makes a duplicate of the current process, identical in almost every way (not everything is copied over, for example, resource limits in some implementations but the idea is to create as close a copy as possible).

The new process (child) gets a different process ID (PID) and has the PID of the old process (parent) as its parent PID (PPID). Because the two processes are now running exactly the same code, they can tell which is which by the return code of fork - the child gets 0, the parent gets the PID of the child. This is all, of course, assuming the fork call works - if not, no child is created and the parent gets an error code.

`Vfork` : The basic difference between vfork and fork is that when a new process is created with vfork(), the parent process is temporarily suspended, and the child process might borrow the parent&#39;s address space. This strange state of affairs continues until the child process either exits, or calls execve(), at which point the parent 
process continues. 

This means that the child process of a vfork() must be careful to avoid unexpectedly modifying variables of the parent process. In particular, the child process must not return from the function containing the vfork() call, and it must not call exit() (if it needs to exit, it should use _exit(); actually, this is also true for the child of a normal fork()). 

`Exec :` The exec call is a way to basically replace the entire current process with a new program. It loads the program into the current process space and runs it from the entry point. exec() replaces the current process with a the executable pointed by the function. Control never returns to the original program unless there is an exec() error.

`Clone :` Clone, as fork, creates a new process. Unlike fork, these calls allow the child process to share parts of its execution context with the calling process, such as the memory space, the table of file descriptors, and the table of signal handlers.

When the child process is created with clone, it executes the function application fn(arg). (This differs from fork, where execution continues in the child from the point of the original fork call.) The fn argument is a pointer to a function that is called by the child process at the beginning of its execution. The arg argument is passed to the fn function. 

When the fn(arg) function application returns, the child process terminates. The integer returned by fn is the exit code for the child process. The child process may also terminate explicitly by calling exit(2) or after receiving a fatal signal. 



Information gotten form : 

 - [https://stackoverflow.com/questions/1653340/exec-and-fork][1]
 - [http://www.allinterview.com/showanswers/59616.html][2]
 - [http://www.unixguide.net/unix/programming/1.1.2.shtml][3]
 - [http://linux.about.com/library/cmd/blcmdl2_clone.htm][4]


Thanks for taking the time to read this ! :)


  [1]: https://stackoverflow.com/questions/1653340/exec-and-fork
  [2]: http://www.allinterview.com/showanswers/59616.html
  [3]: http://www.unixguide.net/unix/programming/1.1.2.shtml
  [4]: http://linux.about.com/library/cmd/blcmdl2_clone.htm

The difference between fork(), vfork(), exec() and clone()

What are the differences between `fork` and `exec`?





Differences between fork and exec

I need in **node.js** function

    result = execSync(&#39;node -v&#39;);

that will **synchronously** execute the given command line and return all stdout&#39;ed by that command text.

&gt; ps. Sync is wrong. I know. Just for personal use.

**UPDATE**

Now we have mgutz&#39;s solution which gives us exit code, but not stdout! Still waiting for a more precise answer.

**UPDATE**

**mgutz** updated his answer and the solution is here :)  
Also, as **dgo.a** mentioned, there is stand-alone module [exec-sync](https://github.com/jeremyfa/node-exec-sync)


**UPDATE 2014-07-30**

[ShellJS](https://github.com/arturadib/shelljs) lib arrived. Consider this is the best choice for now.

-----------

**UPDATE 2015-02-10**

**AT LAST!** NodeJS 0.12 supports `execSync` natively.  
See official [docs](http://nodejs.org/docs/v0.12.0/api/child_process.html#child_process_child_process_execsync_command_options)



node.js execute system command synchronously

Is it possible to execute an external program from within node.js? Is there an equivalent to Python&#39;s `os.system()` or any library that adds this functionality?

How to execute an external program from within Node.js?

I&#39;m trying to run a Python script from PHP using the following command:

`exec(&#39;/usr/bin/python2.7 /srv/http/assets/py/switch.py arg1 arg2&#39;);`

However, PHP simply doesn&#39;t produce any output. Error reporting is set to E_ALL and display_errors is on.

Here&#39;s what I&#39;ve tried:

 - I used `python2`, `/usr/bin/python2` and `python2.7` instead of `/usr/bin/python2.7`
 - I also used a relative path instead of an absolute path which didn&#39;t change anything either.
 - I tried using the commands `exec`, `shell_exec`, `system`.

However, if I run

    if (exec(&#39;echo TEST&#39;) == &#39;TEST&#39;)
    {
        echo &#39;exec works!&#39;;
    }

it works perfectly fine while `shutdown now` doesn&#39;t do anything.

PHP has the permissions to access and execute the file.

EDIT: Thanks to Alejandro, I was able to fix the problem. If you have the same problem, don&#39;t forget that your webserver probably/hopefully doesn&#39;t run as root. **Try logging in as your webserver&#39;s user or a user with similar permissions and try to run the commands yourself.**

Running a Python script from PHP

Consider the following code:

    String commandf = &quot;ls /etc | grep release&quot;;
  
    try {

        // Execute the command and wait for it to complete
        Process child = Runtime.getRuntime().exec(commandf);
        child.waitFor();

        // Print the first 16 bytes of its output
        InputStream i = child.getInputStream();
        byte[] b = new byte[16];
        i.read(b, 0, b.length); 
        System.out.println(new String(b));
	
    } catch (IOException e) {
        e.printStackTrace();
        System.exit(-1);
    }

The program&#39;s output is:

    /etc:
    adduser.co

When I run from the shell, of course, it works as expected:

    poundifdef@parker:~/rabbit_test$ ls /etc | grep release
    lsb-release

The internets tell me that, due to the fact that pipe behavior isn&#39;t cross-platform, the brilliant minds who work in the Java factory producing Java can&#39;t guarantee that pipes work.

How can I do this?

I am not going to do all of my parsing using Java constructs rather than `grep` and `sed`, because if I want to change the language, I&#39;ll be forced to re-write my parsing code in that language, which is totally a no-go.

How can I make Java do piping and redirection when calling shell commands?

How to make pipes work with Runtime.exec()?

How to execute file that I&#39;m editing in Vi(m) and get output in split window (like in SciTE)?

Of course I could execute it like that:

    :!scriptname

But is it posible to avoid writing script name and how to get output in split window instead just bottom of the screen?

How to execute file I&#39;m editing in Vi(m)

I&#39;ve been looking at dynamic evaluation of Python code, and come across the `eval()` and `compile()` functions, and the `exec` statement.

Can someone please explain the difference between `eval` and `exec`, and how the different modes of `compile()` fit in?

What&#39;s the difference between eval, exec, and compile?

I want to know exactly what `{} \;` and `{} \+` and `| xargs ...` do. Please clarify these with explanations.

Below 3 commands run and output same result but the first command takes a little time and the format is also little different. 

    find . -type f -exec file {} \;
    find . -type f -exec file {} \+
    find . -type f | xargs file

It&#39;s because 1st one runs the `file` command for every file coming from the `find` command. So, basically it runs as: 

    file file1.txt
    file file2.txt

But latter 2 find with `-exec` commands run file command once for all files like below:

    file file1.txt file2.txt

Then I run the following commands on which first one runs without problem but second one gives error message.

    find . -type f -iname &#39;*.cpp&#39; -exec mv {} ./test/ \;
    find . -type f -iname &#39;*.cpp&#39; -exec mv {} ./test/ \+ #gives error:find: missing argument to `-exec&#39;

For command with `{} \+`, it gives me the error message 

    find: missing argument to `-exec&#39;

why is that? can anyone please explain what am I doing wrong?



Why does find -exec mv {} ./target/ + not work?

These are all the versions of exec that can be used in C (and C++)

    execl
    execle
    execlp
    execv
    execve
    execvp

What&#39;s the difference between them? How do you know which one to use?

What are the different versions of exec used for in C and C++?

Both will be able to execute commands in container. 
Both could detach the container.

So what is the real difference between docker exec and docker attach?



difference between docker attach and docker exec

How do I execute a string containing Python code in Python?

I have a command I want to run, but I do not want PHP to sit and wait for the result.

    &lt;?php
    echo &quot;Starting Script&quot;;
    exec(&#39;run_baby_run&#39;);
    echo &quot;Thanks, Script is running in background&quot;;
    ?&gt;

Is it possible to have PHP not wait for the result.. i.e. just kick it off and move along to the next command.

I cant find anything, and not sure its even possible.  The best I could find was someone making a CRON job to start in a minute.

php exec command (or similar) to not wait for result

I want to invoke an external command from Kotlin code.

* In C/Perl, I would use the `system()` function.
* In Python, I would use the subprocess module.
* In Go, I would use os/exec, and etc.

But how do I do this in Kotlin?

How to invoke external command from within Kotlin code?

I&#39;m trying to get simple output by exec task with `msbuild`:

    &lt;Project xmlns=&quot;http://schemas.microsoft.com/developer/msbuild/2003&quot;&gt;
      &lt;Target Name=&quot;Test&quot;&gt;
        &lt;Exec Command=&quot;echo test output&quot;&gt;
          &lt;Output TaskParameter=&quot;Outputs&quot; ItemName=&quot;Test1&quot; /&gt;
        &lt;/Exec&gt;
        &lt;Exec Command=&quot;echo test output&quot;&gt;
          &lt;Output TaskParameter=&quot;Outputs&quot; PropertyName=&quot;Test2&quot; /&gt;
        &lt;/Exec&gt;
        &lt;Message Text=&quot;----------------------------------------&quot;/&gt;
        &lt;Message Text=&quot;@(Test1)&quot;/&gt;
        &lt;Message Text=&quot;----------------------------------------&quot;/&gt;
        &lt;Message Text=&quot;$(Test2)&quot;/&gt;
        &lt;Message Text=&quot;----------------------------------------&quot;/&gt;
      &lt;/Target&gt;
    &lt;/Project&gt;

But get next output:

      echo test output
      test output
      echo test output
      test output
      ----------------------------------------
      ----------------------------------------
      ----------------------------------------

How can I get output by my script?

How get exec task output with msbuild

I used this command:  
`docker exec compassionate_mclean cd /root/python`  
 The error returned is 
 

&gt; docker-exec: failed to exec: exec: &quot;cd&quot;: executable file not found in
&gt; $PATH

Kindly help me out

docker-exec failed: &quot;cd&quot;: executable file not found in $PATH

I have a method I am using to execute a command on the local host.  I&#39;d like to add a timeout parameter to the method so that if the command being called doesn&#39;t finish in a reasonable amount of time the method will return with an error code.  Here&#39;s what it looks like so far, without the ability to timeout:

    public static int executeCommandLine(final String commandLine,
                                         final boolean printOutput,
                                         final boolean printError)
        throws IOException, InterruptedException
    {
        Runtime runtime = Runtime.getRuntime();
        Process process = runtime.exec(commandLine);

        if (printOutput)
        {
            BufferedReader outputReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            System.out.println(&quot;Output:  &quot; + outputReader.readLine());
        }

        if (printError)
        {
            BufferedReader errorReader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
            System.out.println(&quot;Error:  &quot; + errorReader.readLine());
        }

        return process.waitFor();
    }


Can anyone suggest a good way for me to implement a timeout parameter?

How to add a timeout value when using Java&#39;s Runtime.exec()?

What is the difference between the following Ruby methods?

`exec`, `system` and `%x()` or *Backticks*

I know they are used to execute terminal commands programmatically via Ruby, but I&#39;d like to know why there are three different ways to do this.

Ruby, Difference between exec, system and %x() or Backticks

What is the difference between `system` and `exec` family commands?  Especially I want to know which one of them creates child process to work?

Difference between &quot;system&quot; and &quot;exec&quot; in Linux?

Can anyone help explain what&#39;s going on with `tmux`, `bash`, and `exec`? I&#39;m trying to set up a tmux session with a 4-pane window. Ideally, I want to run a command in 3 of the panes: e.g. a Ruby Thin server and a couple of Ruby daemons. This is what I have so far:

`~/.bin/tmux-foo`:

    #!/bin/sh
    
    tmux new-session -d -s foo &#39;exec pfoo &quot;bundle exec thin start&quot;&#39;
    tmux rename-window &#39;Foo&#39;
    tmux select-window -t foo:0
    tmux split-window -h &#39;exec pfoo &quot;bundle exec compass watch&quot;&#39;
    tmux split-window -v -t 0 &#39;exec pfoo &quot;rake ts:start&quot;&#39;
    tmux split-window -v -t 1 &#39;exec pfoo&#39;
    tmux -2 attach-session -t foo

`~/.bin/pfoo`:

    #!/bin/bash
    cd ~/projects/foo
    rvm use ree
    
    # here I want to execute command1 2 3 or 4...
    
    exec $SHELL

It all works... but when I `ctlr-c` in the first pane that is running the thin server, it stops the thin server and returns to the shell. However, the command is not in the history; i.e. if I hit the up key I don&#39;t get the `bundle exec thin start` command... I get some other command from my bash history. I&#39;m wondering if there&#39;s any way to arrange these scripts so that I get the commands in the bash history.

Also... I&#39;ve tried many combinations of `exec`, `exec $SHELL -s ...`, and `exec $SHELL -s ... -I` and I&#39;m not quite sure what is going on...

Can anyone help explain the general idea of what is going on with `tmux` and `bash` and `exec` here?

Bash scripts with tmux to launch a 4-paned window

I&#39;m writing a PHP script to be used to check for network connections with Linux shell command `ping` calling it with PHP&#39;s `exec()`:

    &lt;?php
    
    
    // Bad IP domain for testing.
    $domain_bad = &quot;lksjdflksjdf.com&quot;;
    
    $ip_address = $domain_bad;
    
    exec(&quot;ping -c 1 $domain_bad&quot;, $output, $return_var);
    
    var_dump($return_var);
    echo &quot;return_var is: $return_var&quot; . &quot;\n&quot;;
    var_dump($output);
    
    
    exit;
    ?&gt;

I&#39;m not getting the output for the error message from ping in `$output` which is what I&#39;m expecting:

    $ php try.php
    ping: unknown host lksjdflksjdf.com
    int(2)
    return_var is: 2
    array(0) {
    }

If the domain is a good domain, such as yahoo.com, then `$output` has the output from ping in an array. But if it&#39;s an error such as `&#39;ping: unknown host lksjdflksjdf.com&#39;` it doesn&#39;t get returned to the `$output` array.

Why is this happening and is there a better method to do this? 



PHP: Why isn&#39;t exec() returning output?

I&#39;m struggling to understand the difference between `shell_exec()` and `exec()`...

I&#39;ve always used `exec()` to execute server side commands, when would I use `shell_exec()`?

Is `shell_exec()` just a shorthand for `exec()`?  It seems to be the same thing with fewer parameters.

PHP shell_exec() vs exec()

It is possible to run an external command by three PHP functions of

    system();
    exec();
    shell_exec();

but what are their differences? In spite of their specific applications, in most cases, the can be equally used. I am curious to know which is preferred one when they can be equally used. For example, for unzipping a file or compressing a folder (with tar command), which one is preferred (probably from performance point of view)?

**UPDATE:** In another question, I found a very useful **[link][1]** describing different aspects for these functions. I share the link here, as other may use to better understand security issues and other aspects.


  [1]: http://web.archive.org/web/20130809032648/http://chipmunkninja.com/Program-Execution-in-PHP%3A-exec-m@

What are the differences of system(), exec() and shell_exec() in PHP?

I have a bash script, that I run like this via the command line:

    ./script.sh var1 var2

I am trying to execute the above command, after I call a certain php file.

What I have right now is:

	$output = shell_exec(&quot;./script.sh var1 var2&quot;);
	echo &quot;&lt;pre&gt;$output&lt;/pre&gt;&quot;;

But it doesn&#180;t work. I tried it using `exec` and `system` too, but the script never got executed.

However when I try to run `shell_exec(&quot;ls&quot;);` it does work and `$output` is a list of all files.

I am not sure whether this is because of a limitation of the VPS I am using or if the problem is somewhere else?

Run Bash Command from PHP

When I run the code below:

	cmd := exec.Command(&quot;find&quot;, &quot;/&quot;, &quot;-maxdepth&quot;, &quot;1&quot;, &quot;-exec&quot;, &quot;wc&quot;, &quot;-c&quot;, &quot;{}&quot;, &quot;\\&quot;)
	var out bytes.Buffer
	cmd.Stdout = &amp;out
	err := cmd.Run()
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(&quot;Result: &quot; + out.String())

I am getting this error:

&gt; exit status 1

However this is not helpful to debug the exact cause of the error.

How to get more detailed information?

How to debug &quot;exit status 1&quot; error when running exec.Command in Golang

In PHP I am executing a command with exec(), and it returns if successful an URL;

    $url = exec(&#39;report&#39;);

However, I want to check stderr, if something went wrong. How would I read the stream?
I want to use php://stderr, but I am not sure how to use it.

PHP StdErr after Exec()

What are the differences?

Is there a specific situation or reason for each function? If yes, can you give some examples of those situations?

PHP.net says that they are used to execute external programs. [see reference][1]
From the examples I see, I don&#39;t see any obvious difference.

If I were to simply run a script (bash or python), which function do you recommend me to use?


  [1]: http://php.net/manual/en/function.exec.php

PHP exec() vs system() vs passthru()

I am working on a program written in Java which, *for some actions*, launches external programs using user-configured command lines.  Currently it uses `Runtime.exec()` and does not retain the `Process` reference (the launched programs are either a text editor or archive utility, so no need for the system in/out/err streams).

There is a minor problem with this though, in that when the Java program exits, it doesn&#39;t really quit until all the launched programs are exited.  

I would greatly prefer it if the launched programs were completely independent of the JVM which launched them.

The target operating system is multiple, with Windows, Linux and Mac being the minimum, but any GUI system with a JVM is really what is desired (hence the user configurability of the actual command lines).

Does anyone know how to make the launched program execute completely independently of the JVM?

---

**Edit in response to a comment**

The launch code is as follows.  The code may launch an editor positioned at a specific line and column, or it may launch an archive viewer.  Quoted values in the configured command line are treated as ECMA-262 encoded, and are decoded and the quotes stripped to form the desired exec parameter.

The launch occurs on the EDT.

    static Throwable launch(String cmd, File fil, int lin, int col) throws Throwable {
        String frs[][]={
            { &quot;$FILE$&quot;  ,fil.getAbsolutePath().replace(&#39;\\&#39;,&#39;/&#39;) },
            { &quot;$LINE$&quot;  ,(lin&gt;0 ? Integer.toString(lin) : &quot;&quot;) },
            { &quot;$COLUMN$&quot;,(col&gt;0 ? Integer.toString(col) : &quot;&quot;) },
            };
        String[] arr; // array of parsed tokens (exec(cmd) does not handle quoted values)

        cmd=TextUtil.replace(cmd,frs,true,&quot;$$&quot;,&quot;$&quot;);
        arr=(String[])ArrayUtil.removeNulls(TextUtil.stringComponents(cmd,&#39; &#39;,-1,true,true,true));
        for(int xa=0; xa&lt;arr.length; xa++) {
            if(TextUtil.isQuoted(arr[xa],true)) {
                arr[xa]=TextDecode.ecma262(TextUtil.stripQuotes(arr[xa]));
                }
            }
        log.println(&quot;Launching: &quot;+cmd);
        Runtime.getRuntime().exec(arr);
        return null;
        }

---

This appears to be happening only when the program is launched from my IDE.  I am closing this question since the problem exists only in my development environment; **it is not a problem in production**.  From the test program in one of the answers, and further testing I have conducted I am satisfied that it is not a problem that will be seen by any user of the program on any platform.

All Exec Solutions on Gang of Coders

Total of 36 Exec Solutions

sh command: exec 2>&1

Why doesn't exec work in a function with a subfunction?