Просмотр исходного текста страницы C++/String/string substr

==Find substring day in a string and check if it was found==


   
<source lang="cpp">  
#include <string>
#include <iostream>
int main ()
{
    using namespace std;
    string strSample ("this is a test");
    size_t nOffset = strSample.find ("test", 0);
    // Check if the substring was found...
    if (nOffset != string::npos)
        cout << "found:" << nOffset;
    else
        cout << "not found." << endl;
    return 0;
}
  
    
  </source>


==Obtain a substring==


   
<source lang="cpp">  
#include <iostream>
#include <string>
using namespace std;
int main()
{
  string str1("this is a test");
  cout << "  str1: " << str1 << endl;
  // Obtain a substring.
  str1 = str1.substr(5, 4);
  cout << str1 << "\n\n";

  return 0;
}
  
    
  </source>


==Split file name in command line into base name and extension==


   
<source lang="cpp">  
 
/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <string>
using namespace std;
int main (int argc, char* argv[])
{
    string filename, basename, extname, tmpname;
    const string suffix("tmp");
    /* for each command-line argument
     * (which is an ordinary C-string)
     */
    for (int i=1; i<argc; ++i) {
        // process argument as file name
        filename = argv[i];
        
        // search period in file name
        string::size_type idx = filename.find(".");
        if (idx == string::npos) {
            // file name does not contain any period
            tmpname = filename + "." + suffix;
        }
        else {
            /* split file name into base name and extension
             * - base name contains all characters before the period
             * - extension contains all characters after the period
             */
            basename = filename.substr(0, idx);
            extname = filename.substr(idx+1);
            if (extname.empty()) {
                // contains period but no extension: append tmp
                tmpname = filename;
                tmpname += suffix;
            }
            else if (extname == suffix) {
                // replace extension tmp with xxx
                tmpname = filename;
                tmpname.replace (idx+1, extname.size(), "xxx");
            }
            else {
                // replace any extension with tmp
                tmpname = filename;
                tmpname.replace (idx+1, string::npos, suffix);
            }
        }
        // print file name and temporary name
        cout << filename << " => " << tmpname << endl;
    }
}
        
    
  </source>


==string member function substr==


   
<source lang="cpp">  
 
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
   string s1( "AA1234567890asdfasdf" );
   string s2( " AAB" );
   string s3;
   // test string member function substr
   cout << "The substring of s1 starting at location 0 for\n"
      << "14 characters, s1.substr(0, 14), is:\n"
      << s1.substr( 0, 14 ) << "\n\n";
   return 0;
}
/* 
The substring of s1 starting at location 0 for
14 characters, s1.substr(0, 14), is:
AA1234567890as

 */        
    
  </source>


==substr "to-end-of-string" option==


   
<source lang="cpp">  
 
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
   string s1( "AA1234567890asdfasdf" );
   string s2( " AAB" );
   string s3;
   // test substr "to-end-of-string" option
   cout << "The substring of s1 starting at\n"
      << "location 5, s1.substr(5), is:\n"
      << s1.substr( 5 ) << endl; 
   return 0;
}
/* 
The substring of s1 starting at
location 5, s1.substr(5), is:
4567890asdfasdf
 */        
    
  </source>