For instance, if the program does a specific task, say, generate a report, then you will want to know when that program ends so that you can take the next action say, display or print the report. You can find out when the launched program ends, but not if you launch it via ShellExecute. That brings us to ShellExecuteEx This works just like ShellExecute, except that you need to populate a structure rather than just set function parameters.
It has a couple of other features, including the one we're going to use: It returns a HANDLE that can be used to see when the Launched program terminates. Exe"; rSEI. That means that the user could close your program, which puts you in a sort of limbo. A better technique is to not sit there in a loop pumping messages, but rather set a timer and use it to check every so often to see if rSEI. Start the next step. It's rather uncommon these days, but I'd like to cover it for completeness.
If you launch a console application, it might output a series of lines of text to the screen as it operates. Later, you can process the resulting file output. The more complex situation is when that console program outputs a continuous stream of text and you'd like to display or otherwise process it in realtime. To do that, you'll need to set up a pipe and monitor it as it fills up.
All this is leading to the examples of CreateProcess which, when all is said and done, is where each of these other launching options end up, anyway. If you do that, and if the program pathname contains any embedded spaces, be sure to enclose that part of the command line in double quotes. You can use it to maintain contact with the program in the same way that we did in the earlier ShellExecuteEx example.
Then, while the process is running, we read from the pipe and process the data. In the following example, I'm just taking the textual data from the pipe and appending it to the text of an Edit control in the dialog. For instance, this would let you perform elevated administrative actions Interestingly, there is an undocumented variation of ShellExecute that provides a similar capability.
If you set the operation verb to "runas" then you can elevate the privilege level under which the process will run. The shell pops up the Run As dialog box and lets you select a different user and enter the password. It appears to to run Cmd. It clearly hearkens back to the days of memory-limited single-tasking computers. I don't recommend spending much time with these last three options. If you need to run an external program from your own application, you should first look at ShellExecute.
Otherwise, the new program will inherit the extra privileges when it should not. Another function provided by the standard C runtime library for executing programs is system. There are two reasons why you should never use the system function:. The new process executes the shell with execve while the original process waits for the new process to terminate.
The system function therefore does not return control to the caller until the specified program has completed. Yet another function, popen , works somewhat similarly to system. In addition, it returns control to the caller immediately with a FILE object connected to the created pipe so that the caller can communicate with the new program. When communication with the new program is finished, you should call pclose to clean up the file descriptors and reap the child process created by the call to fork.
You should also avoid using popen and its accompanying pclose function, but popen does have utility that is worth duplicating in a secure fashion. The following implementation with a similar API does not make use of the shell. If you do wish to use either system or popen , be extremely careful. First, make sure that the environment is properly set, so that there are no Trojan environment variables.
This means that you must ensure that there is no way an attacker can pass malicious data to the shell command. If possible, pass in a fixed string that the attacker cannot manipulate. If the user must be allowed to manipulate the input, only very careful filtering will accomplish this securely. We recommend that you avoid this scenario at all costs.
Improve this question. Donald Duck 7, 19 19 gold badges 67 67 silver badges 87 87 bronze badges. Lukas Belck Lukas Belck 17 1 1 silver badge 7 7 bronze badges. The system function waits for the executed command to complete. On Linux or Mac you would either fork or run a command that starts your external executable in the background.
But Windows does not have fork , and I'm not sure it has background processes as such, either. You'll need an appropriate function from the Windows API.
I will try to find it. Add a comment. Active Oldest Votes. Improve this answer. Donald Duck Donald Duck 7, 19 19 gold badges 67 67 silver badges 87 87 bronze badges. It worked thanks! But when i tried system notepad for testing it opened the notepad and stoped the program until i close the notepad but with the LeagueClient. Sign up or log in Sign up using Google.
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