C++ Tutorial/Data Types/string function

Convert a string to uppercase.

<source lang="cpp">#include <iostream>

1. include <cstring>
2. include <cctype>

using namespace std;

int main() {

 char str[80]; 
 int i; 

 strcpy(str, "this is a test"); 

 for(i=0; str[i]; i++) str[i] = toupper(str[i]); 

 cout << str; 

 return 0; 

}</source>

THIS IS A TEST

strcpy, strlen, strcmp, strcat

<source lang="cpp">#include <iostream>

1. include <cstdio>
2. include <cstring>

using namespace std;

int main() {

 char s1[80], s2[80]; 

 strcpy(s1, "C++"); 
 strcpy(s2, " is power programming."); 

 cout << "lengths: " << strlen(s1); 
 cout << " " << strlen(s2) << "\n"; 

 if(!strcmp(s1, s2))  
    cout << "The strings are equal\n"; 
 else cout << "not equal\n"; 
  
 strcat(s1, s2); 
 cout << s1 << "\n"; 

 strcpy(s2, s1); 
 cout << s1 << " and " << s2 << "\n"; 

 if(!strcmp(s1, s2)) 
   cout << "s1 and s2 are now the same.\n"; 

 return 0; 

}</source>

lengths: 3 22
not equal
C++ is power programming.
C++ is power programming. and C++ is power programming.
s1 and s2 are now the same.

Using strcat and strncat.

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <cstring>

using std::strcat; using std::strncat; int main() {

  char s1[ 20 ] = "123456";
  char s2[] = "abcdefghi";
  char s3[ 40 ] = "";
  strcat( s1, s2 );
  cout << s1 << "\ns2 = " << s2;
  strncat( s3, s1, 6 ); // places "\0" after last character
  cout << s1 << "\ns3 = " << s3;
  strcat( s3, s1 );
  cout << s1 << "\ns3 = " << s3 << endl;
  return 0;

}</source>

123456abcdefghi
s2 = abcdefghi123456abcdefghi
s3 = 123456123456abcdefghi
s3 = 123456123456abcdefghi

Using strcmp and strncmp

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <iomanip>

using std::setw;

1. include <cstring>

using std::strcmp; using std::strncmp; int main() {

  char *s1 = "abc";
  char *s2 = "abC";
  char *s3 = "Abc";

  cout << "s1 = " << s1 << "\ns2 = " << s2 << "\ns3 = " << s3 
     << "\n\nstrcmp(s1, s2) = " << strcmp( s1, s2 ) 
     << "\nstrcmp(s1, s3) = " << strcmp( s1, s3 ) 
     << "\nstrcmp(s3, s1) = " << strcmp( s3, s1 );
  cout << "\n\nstrncmp(s1, s3, 6) = "
     << strncmp( s1, s3, 2 ) << "\nstrncmp(s1, s3, 7) = " 
     << strncmp( s1, s3, 2 ) << "\nstrncmp(s3, s1, 7) = " 
     << strncmp( s3, s1, 5 ) << endl;
  return 0;

}</source>

s1 = abc
s2 = abC
s3 = Abc
strcmp(s1, s2) = 1
strcmp(s1, s3) = 1
strcmp(s3, s1) = -1
strncmp(s1, s3, 6) = 1
strncmp(s1, s3, 7) = 1
strncmp(s3, s1, 7) = -1

Using strcpy()

<source lang="cpp">#include <iostream>

#include <string.h>

int main()
{
    char String1[] = "test";
    char String2[80];

    strcpy(String2,String1);

    std::cout << "String1: " << String1 << std::endl;
    std::cout << "String2: " << String2 << std::endl;
    return 0;
}</source>

String1: test
String2: test

Using strlen

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <cstring>

using std::strlen; int main() {

  char *string1 = "asdfasdfasdfasdf";
  char *string2 = "     f    ";
  char *string3 = "       ";
  cout << "The length of \"" << string1 << "\" is " << strlen( string1 )
     << "\nThe length of \"" << string2 << "\" is " << strlen( string2 )
     << "\nThe length of \"" << string3 << "\" is " << strlen( string3 ) 
     << endl;
  return 0;

}</source>

The length of "asdfasdfasdfasdf" is 16
The length of "     f    " is 10
The length of "       " is 7

Using strncpy()

<source lang="cpp">#include <iostream>

#include <string.h>

int main()
{
    const int MaxLength = 80;
    char String1[] = "test";
    char String2[MaxLength+1];

    strncpy(String2,String1,MaxLength);
    String2[strlen(String1)] = "\0"; // add a null to the end
    std::cout << "String1: " << String1 << std::endl;
    std::cout << "String2: " << String2 << std::endl;
    return 0;
}</source>

String1: test
String2: test

Using strtok

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <cstring>

using std::strtok; int main() {

  char sentence[] = "a c d e f g e a c d e y gb ";
  char *tokenPtr;
  tokenPtr = strtok( sentence, " " );
  while ( tokenPtr != NULL ) 
  {
     cout << tokenPtr << "\n";
     tokenPtr = strtok( NULL, " " );
  }
  return 0;

}</source>

a
c
d
e
f
g
e
a
c
d
e
y
gb