Programming

I'm attempting to execute a system command contained within a variable, such as;

abfile = "fred"
abdest = "/home"
ab = "scp " + abfile + abdest;
system(ab);

abfile & abdest will be populated via a prompt so will differ each time the script is run.

The system command does not do anything with the variable, but works fine if I put the command in place of the 'ab' variable, should I be using something other than system to execute the contents of the variable ?

system() takes a C string. You're giving it a C++ string, it'll have to be converted before system(), a C function, can use it. Try system(ap.c_str());

That works, many thanks.

i think, that you should use sprintf.

like this:

Code:

abdest = "/home";
sprintf(ab,"%s %s%s", scp, abfile, abdest);
system(ab);

if you do not understand this, check sprintf manual on cplusplus.com

I don't think that will work, since none of those are C-strings.

eu, i am sorry, i didnt realize that we're talking about C (not c++)

edit: but in the title, there is " Question C++ using system() ", we are using c++, so we can save that values to *char, it should work then..

sprintf is a C function, it cannot use a C++ string object as it's output, even in C++. C++ strings cast to const char *, not char *, and that's an important distinction -- it's const because you're not supposed to write to it. There's no way to overload accesses to a pointer -- if you do, it's no longer a pointer -- so it'll never know to allocate memory to hold what you're writing to it. For example, if it's holding "Hello", and you write "hello12345676" to it, the "12345676" bit might overwrite class members or anything else nearby in the heap.

They will work as inputs, as long as you use object.c_str() instead of just object.