c++ - cannot convert 'std::basic_string<char>' to 'const char*' for argument '1' to 'int system(const char*)'

Question

I get this error: "invalid operands of types 'const char*' and 'const char [6]' to binary 'operator+'" when i try to compile my script. Here should be the error:

string name = "john";
system(" quickscan.exe resolution 300 selectscanner jpg showui showprogress filename '"+name+".jpg'");

Answer 1

The type of expression

" quickscan.exe resolution 300 selectscanner jpg showui showprogress filename '"+name+".jpg'"

is std::string. However function system has declaration

int system(const char *s);

that is it accepts an argumnet of type const char *

There is no conversion operator that would convert implicitly an object of type std::string to object of type const char *.

Nevertheless class std::string has two functions that do this conversion explicitly. They are c_str() and data() (the last can be used only with compiler that supports C++11)

So you can write

string name = "john";

system( (" quickscan.exe resolution 300 selectscanner jpg showui showprogress filename '"+name+".jpg'").c_str() );

There is no need to use an intermediate variable for the expression.