CODEWITHSUNDEEP
c++linuxubuntuipcmsgrcv
CoderInNeed
CoderInNeed

Reputation: 41

How to fix string declaration error in scope

I'm trying to run an interprocess communication program but it says string is not declared in the scope as is and when I add #inlcude I get an error that says: 

receiver.cpp:25:35: error: invalid conversion from ‘char*’ to ‘int’ [-fpermissive]
     string temp = to_string(argv[0]);
                             ~~~~~~^
In file included from /usr/include/c++/7/string:52:0,
                 from receiver.cpp:14:
/usr/include/c++/7/bits/basic_string.h:6419:3: note: candidate: std::__cxx11::string std::__cxx11::to_string(unsigned int) <near match>
   to_string(unsigned __val)
   ^~~~~~~~~
receiver.cpp:27:26: error: cannot convert ‘std::__cxx11::string {aka std::__cxx11::basic_string<char>}’ to ‘const char*’ for argument ‘1’ to ‘int atoi(const char*)’
     int msgid = atoi(temp) //Converts message id from string to integer
                          ^
receiver.cpp:45:32: error: ‘some_data’ was not declared in this scope
     if (msgrcv(msgid, (void *)&some_data, BUFSIZ, msg_to_receive, 0) == -1) { //revieces message from message queue
                                ^~~~~~~~~
receiver.cpp:49:29: error: ‘some_data’ was not declared in this scope
     printf("You wrote: %s", some_data.some_text);

This is my code:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.H>
#include <cstring.h>
#include <unist.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <cstdlib>
#inlcude <string>

using namespace std;

struct my_msg_st{
long int my_msg_type;
char some_text[BUFSIZ];
};

int main(int argc, char *argv[0]){
int running =1;
string temp = to_string(argv[0]);
int msgid = atoi(temp);
struct my_msg_st some_data;
long int msg_to_receive = 0;

....

if (strncmp(some_data.some_text, "end", 3) == 0){
    running =0;
}

...
exit(0);
}

expecting for the code to print out the message sent from the sender file

Upvotes: -1

Views: 382

Answers (1)

Thomas Matthews
Thomas Matthews

Reputation: 57678

Here are some fixes for your issues:
string temp = to_string(argv[0]);
1. to_string converts numbers to string. the argv[0] is a C-style string, not a number.
2. The std::string constructor already has a version to convert from char * to std::string.

atoi(temp)
1. The atoi function takes a parameter of type char * not std::string. You'll need to use atoi(temp.c_str()) or prefer std::ostringstream.

Please review the differences between char arrays (a.k.a. C-Style strings) and the std::string type. Prefer to use std::string, especially in structures.

Carefully read the library function descriptions before using them.

See also std::ostringstream. Since this is C++, prefer to use C++ I/O such as std::cout and operator <<.

Upvotes: 0

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