Convert all and any command line input to string in C++ -

i trying write small code @ beginning of program runs different functions depending on file extension of files passed when calling program command line.

i want convert argv[2] string (called st) can compare ".png", ".txt", etc. using strccmp.

i found similar solutions around so, none of them addressed issue of saving argument string variable. whenever try use argv[1] or argv[2], debugger complains subscript out of range, , @ loss how around this.

int main(int argc, char** argv) {     // first , simplest attempt     sd::string st = argv[2];      // second attempt fails     std::vector<std::string> all_arg;      if (argc > 1) {         all_arg.assign(argv + 1, argv + argc);     }      std::string st = all_arg[2];       // comparison     st = st.substr(st.size() - 4, st.size() - 1);     if (strcmp(st.c_str(), ".png")) { ... }     else {...}        } 

corrected obvious problems, code compiles , runs fine.

#include <iostream> #include <vector> #include <string>  int main( int argc, char ** argv ) {     std::vector< std::string > all_arg;     if ( argc > 1 )     {         all_arg.assign( argv + 1, argv + argc );     }      ( auto str : all_arg )     {         std::cout << str << "\n";     } } 

as comparison, looks fishy in more 1 way...

st = st.substr(check.size() - 4, check.size() - 1); 

aside check not being defined, happens if string shorter 4 characters...?

if (strcmp(st.c_str(), ".png")) { ... } 

err... degrading string char array through c_str() , going through c function strcmp()? for?

try this:

for ( auto str : all_arg ) {     std::string extension;     std::string::size_type length = str.length();      if ( length >= 4 )     {          extension = str.substr( size - 4 );     }      if ( extension == ".png" )     {         std::cout << str << "is png!\n";     } } 

and think above being case-sensitive, , once think converting str lowercase prior comparing, consider locale, might include unicode. ;-)