How to embedd Linux commands in C++ code and how to use the output of those commands

[itskamakshi]

Hi All,

I have developed an application in cpp , now I have to use few linux commands in cpp application and have to use the results of those linux commands to manipulate my application.

Please help me how can I embedd and use its result of linux commands in cpp applications.

some of the linux commands are as follows :

- iwconfig
- iwlist
- iwspy
- iwpriv
- ifrename

Please suggest how to use it in cpp.

Regards,
Kamakshi

[Lakshmipathi]

From C program , you can always use function like system() to execute a command. Check whether C++ has system() function or similar functions.

[Rubberman]

As Lakshmipathi said, you can use the system() function to execute a shell script. If you want to use the output from them to affect futher processing of your application then you will need to redirect the output of these commands to a file and read the file after the command completes.

[Cabhan]

First off, right after I post this, I will move this thread into the programming forum.

Secondly, it depends on what exactly you are trying to accomplish.

If all that you want to do is execute a program, then system() is usually the way to go. system() takes a commandline, and then runs it. For instance:

system("iwconfig");

This would run the "iwconfig" command, and would print out whatever it would output.

However, if you want to use the output of this command in your own program, then system() isn't very good. Instead, you want a function that I don't believe C++ has, but which C does. This function is called popen(). popen() creates a pipe: it launches the given program, but redirects that program's output into a new filehandle in your program. This allows you to read the output directly in your program, and do whatever you want.

Because this is not a C++ function, it doesn't integrate very nicely with C++ functions. However, Googling for "popen c++" does reveal some C++ wrappers around popen() which might work nicely.

I hope this helps.

[tetsujin]

As Lakshmipathi said, you can use the system() function to execute a shell script. If you want to use the output from them to affect futher processing of your application then you will need to redirect the output of these commands to a file and read the file after the command completes.

(EDIT): Stupid me, Cabhan already provided this information...

Well, that's not entirely true, of course... When the shell runs a command pipeline, it routes the stdin/stdout of commands being run to pipes to connect them together. Clearly one could use the same sequence of system calls (i.e. pipe(), fork(), exec()) to run a program and have access to its I/O as it runs...

This basic functionality is also provided by the POSIX popen() call, which is like system() except that it gives you a file stream for a pipe that connects to either the process's input or its output (can't do both at the same time with popen(), unfortunately.)

Working with a C FILE* in C++ isn't ideal of course - unless you happen to prefer cstdio over iostream... I think if I were doing it I'd create a C++ class that goes through the equivalent system calls but creates an iostream - unless there happens to be a convenient way to wrap a FILE* as an iostream... Or if Boost provides such a thing, that would work, too.