CODEWITHSUNDEEP
linuxstringintatoi
TheEmeritus
TheEmeritus

Reputation: 419

Can't convert STRING to INT in C++ in LINUX

I've tried many ways, as detailed in here: http://www.cplusplus.com/forum/general/13135/

Most of them work if I run the file on Windows, but when I try to do so on LINUX, none of them works. For example, I try to do:

  string str = "123";
  int sp;
  istringstream ( str ) >> sp;

But it gives me the error: "invalid use of incomplete type ‘struct std::istringstream’ /usr/include/c++/4.4/iosfwd:67: error: declaration of ‘struct std::istringstream’"

Other option was 'atoi', but it says that 'atoi was not defined in this scope.'

Any ideas why its happening?

Upvotes: 2

Views: 5411

Answers (2)

Sergey K.
Sergey K.

Reputation: 25386

The POSIX way to covert std::string to int will be atoi()

#include <cstdlib>
...
string str = "123";
int sp = atoi( str.c_str() );

If you want to convert not only to int but to many types, it is better to use stringstream. However, beware the increased compilation time.

Upvotes: 3

Evert
Evert

Reputation: 593

as for the atoi() function, you need to include the cstdlib (#include <cstdlib>) header.

then you can use it like this:

string str= "123"; 
int sp = atoi(str.c_str());

it will tell the string object to act as a const char* pointing to a C-style string (most probably best known as a string with the zero terminator \0).

Upvotes: 5

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