I need to create a simple tool for to add to my C# program.
If "chrome.exe" is running then
Me Close
how can I accomplish that in C++?
You can use System("query process > file.txt"); and then use functions like fopen to opent file.txt and then load list of processes to an array and then make if statement and search for yourprocessname.exe - and when condition is positive exit() function to close the program.
The C++ language has no knowledge of the concept of "process". In C++, there is no standard way to query whether another process exists. Such query must be made through the API of the operating system. First step is to know what operating system the program will be run on. Second step is to read the documentation of that OS.
Related
Let's say I want to call a C++ program from Clojure, like stockfish.
If I execute stockfish from the terminal, it stays open and interactive until the command is quit.
However, if I call from Clojure, it just calls it once and closes it.
I have used the programs macro of the me/conch package, like this:
user> (programs stockfish)
user> (stockfish "uci")
"Stockfish 030620 64 by T. Romstad ... \nuciok\n"
And the program stops. How can I get the process to stay open and to keep interacting until I tell it to quit?
This sort of problem has a canonical solution in the Unix expect tool, which has been replicated in, for example, Perl's Expect module. There might also be a Java version of Expect. If so, it might be a more direct solution.
About conch specifically, the README.md at https://github.com/Raynes/conch presents two ways of invoking a program. The first way is easy, but sends only one burst of standard input before closing the program, as you observed. The second way will be harder to work with, but you can send more input whenever you want by writing to the process' standard-input, and recover output whenever you want by reading from its standard-output. It's under the heading https://github.com/Raynes/conch#low-level-usage. It looks like a thin wrapper around the Java process API, which you might as well use directly.
i want to do a simple program that will run another program (easy task in C++), hook the process and, when the program is closed, run another program (needed to sync a file modified by the first program).
The second program prompt out a popout asking a simple Yes/No buttons.
There is any way?
I am writing an article about hooking : http://ntvalk.blogspot.nl/2013/11/hooking-explained-detouring-library.html
It describes the probably most common methods for hooking under Windows. (jmp/vtable/etc)
gldraphael already described a method of running another program.
Check this out: http://faq.cprogramming.com/cgi-bin/smartfaq.cgi?answer=1044654269&id=1043284392
It lists the various ways you can run another program.
I know that in a DOS/Windows application, you can issue system commands from code using lines like:
system("pause");
or
system("myProgram.exe");
...from stdlib.h. Is there a similar Linux command, and if so which header file would I find it in?
Also, is this considered bad programming practice? I am considering trying to get a list of loaded kernal modules using the lsmod command. Is that a good idea or bad idea? I found some websites that seemed to view system calls (at least system("pause");) in a negative light.
system is a bad idea for several reasons:
Your program is suspended until the command finishes.
It runs the command through a shell, which means you have to worry about making sure the string you pass is safe for the shell to evaluate.
If you try to run a backgrounded command with &, it ends up being a grandchild process and gets orphaned and taken in by the init process (pid 1), and you have no way of checking its status after that.
There's no way to read the command's output back into your program.
For the first and final issues, popen is one solution, but it doesn't address the other issues. You should really use fork and exec (or posix_spawn) yourself for running any external command/program.
Not surprisingly, the command is still
system("whatever");
and the header is still stdlib.h. That header file's name means "standard library", which means it's on every standard platform that supports C.
And yes, calling system() is often a bad idea. There are usually more programmatic ways of doing things.
If you want to see how lsmod works, you can always look-up its source code and see what the major system calls are that it makes. Then use those calls yourself.
A quick Google search turns up this link, which indicates that lsmod is reading the contents of /proc/modules.
Well, lsmod does it by parsing the /proc/modules file. That would be my preferred method.
I think what you are looking for are fork and exec.
I have a c++ program (very complicated, and lengthy both in code and execution time).
Once in a while this program stops and calls a user-specified shell script.
Before calling the script, my program creates a .out file with current data. I call the script via system() command. The script then reads the .out file, and creates its own script.out file and exits.
Then the system() function call ends, and my program reads and parses the script.out file.
Question: is there a better way to execute communication between my c++ program and a random shell script?
My intent is to have full communication between the two. Script could virtually "ask" the program "What data do you have right now?" and the program would reply with some strict convention. Then the script could say "Add this data...", or "delete all your previous data" etc.etc.
The reason I need this is because the shell script tells the program to modify its data. The exact data that was put in the original .out file. So after the modification is done -- the actual data held by the program does not correspond to the data written in the .out file.
Thanks!
P.S.
I swear I've searched around, but everyone suggests an intermediate file.
There are certainly ways to do that without intermediate files. The most common approach is to use command line arguments for input, and pipes for standard output; others also use pipes for input. The most straight-forward alternative to system then is to use popen.
On a unix-like system? Perhaps pipe (2) will work for you?
From the man page (Mac OS X 10.5 version):
SYNOPSIS
#include <unistd.h>
int pipe(int fildes[2]);
DESCRIPTION
The pipe() function creates a pipe (an object that allows unidirectional
data flow) and allocates a pair of file descriptors. The first descrip-
tor connects to the read end of the pipe; the second connects to the
write end.
You will, of course, have to follow the creation of the pipes with a fork and exec pair. Probably this has already been answered in detail, and now you know what to search on...
It's been a while since I did this, but:
In the main process, before forking the sub-process you call pipe twice. Now you have two pipes and control both ends of both of them.
You fork.
The main process will read from one pipe and write from the other. It doesn't matter which is which, but you need to be clear about this.
The child process will call one of the exec family of function to replace it's image with that of the shell you want to run but first you will use dup2 to replace it's standard input and output with the ends of the two pipes (again, this is where you need to be clear about which pipe is which).
At his point you have two processes, the main process can send things into one pipe ad they will be received on the standard input of the script, and anything the script writes to it's standard output will be sent up the other pipe to the controlling process. So they take turns, just like interacting with the shell.
You can use pipes or (maybe more convenient) sockets - for example frontends to gdb, or expect do that. It would require changes to your shell scripts, and switching from system() to more low-level fork() and exec().
It's rather complicated so please, be more specific about your environment and what you need to clarify.
You are asking the question on Interprocess Communication (IPC).
There are a lot of ways to do that. You can do a simply search and Internet will return you most answers.
If I am not wrong, Google chrome uses a technique called Named Pipe.
Anyway, I think the most "portable way" is probably a file. But if you know you are working on which operating system, you can definitely use most of the IPC techniques.
I have a project that I thought was going to be relatively easy, but is turning out to be more of a pain that I had hoped. First, most of the code I'm interacting with is legacy code that I don't have control over, so I can't do big paradigm changes.
Here's a simplified explanation of what I need to do: Say I have a large number of simple programs that read from stdin and write to stdout. (These I can't touch). Basically, input to stdin is a command like "Set temperature to 100" or something like that. And the output is an event "Temperature has been set to 100" or "Temperature has fallen below setpoint".
What I'd like to do is write an application that can start a bunch of these simple programs, watch for events and then send commands to them as necessary. My initial plan was to something like popen, but I need a bidrectional popen to get both read and write pipes. I hacked something together that I call popen2 where I pass it the command to run and two FILE* that get filled with the read and write stream. Then all I need to do is write a simple loop that reads from each of the stdouts from each of the processes, does the logic that it needs and then writes commands back to the proper process.
Here's some pseudocode
FILE *p1read, *p1write;
FILE *p2read, *p2write;
FILE *p3read, *p3write;
//start each command, attach to stdin and stdout
popen2("process1",&p1read,&p1write);
popen2("process2",&p2read,&p2write);
popen2("process3",&p3read,&p3write);
while (1)
{
//read status from each process
char status1[1024];
char status2[1024];
char status3[1024];
fread(status1,1024,p1read);
fread(status2,1024,p2read);
fread(status3,1024,p3read);
char command1[1024];
char command2[1024];
char command3[1024];
//do some logic here
//write command back to each process
fwrite(command1,p1write);
fwrite(command2,p2write);
fwrite(command3,p3write);
}
The real program is more complicated where it peeks in the stream to see if anything is waiting, if not, it will skip that process, likewise if it doesn't need to send a command to a certain process it doesn't. But this code gives the basic idea.
Now this works great on my UNIX box and even pretty good on a Windows XP box with cygwin. However, now I need to get it to work on Win32 natively.
The hard part is that my popen2 uses fork() and execl() to start the process and assign the streams to stdin and stdout of the child processes. Is there a clean way I can do this in windows? Basically, I'd like to create a popen2 that works in windows the same way as my unix version. This way the only windows specific code would be in that function and I could get away with everything else working the same way.
Any Ideas?
Thanks!
On Windows, you invoke CreatePipe first (similar to pipe(2)), then CreateProcess. The trick here is that CreateProcess has a parameter where you can pass stdin, stdout, stderr of the newly-created process.
Notice that when you use stdio, you need to do fdopen to create the file object afterwards, which expects file numbers. In the Microsoft CRT, file numbers are different from OS file handles. So to return the other end of CreatePipe to the caller, you first need _open_osfhandle to get a CRT file number, and then fdopen on that.
If you want to see working code, check out _PyPopen in
http://svn.python.org/view/python/trunk/Modules/posixmodule.c?view=markup
I think you've made a very good start to your problem by using the popen2() function to abstract away the cross-platform issues. I was expecting to come and suggest 'sockets', but I'm sure that's not relevant after reading the question. You could use sockets instead of pipes - it would be hidden in the popen2() function.
I am 99% sure you can implement the required functionality on Windows, using Windows APIs. What I cannot do is point you to the right functions reliably. However, you should be aware the Microsoft has most of the POSIX-like API calls available, but the name is prefixed with '_'. There are also native API calls that achieve the effects of fork and exec.
Your comments suggest that you are aware of issues with availability of data and possible deadlocks - be cautious.