How to get length of a string using strlen function

Question

I have following code that gets and prints a string    include lt iostream gt   include lt conio h gt   include lt string gt  using namespace std   int main         string str      cout  lt  lt   Enter a string         getline cin  str       cout  lt  lt  str      getch        return 0      But how to count the number of characters in this string using strlen   function

User · Answer

Use std  string  size or std  string  length  both are the same    As you insist to use strlen  you can    int size   strlen  str c str        note the usage of std  string  c str  which returns const char     BUT strlen counts untill it hit  0 char and std  string can store such chars  In other words  strlen could sometimes lie for the size

User · Answer

Simply use      int len str length

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If you really  really want to use strlen    then  cout  lt  lt  strlen str c str     lt  lt  endl    else the use of  length   is more in keeping with C

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For C   strings  there s no reason to use strlen  Just use string  length   std  cout  lt  lt  str length    lt  lt  std  endl    You should strongly prefer this to strlen str c str    for the following reasons    Clarity  The length    or size    member functions unambiguously give back the length of the string  While it s possible to figure out what strlen str c str    does  it forces the reader to pause for a bit  Efficiency  length   and size   run in time O 1   while strlen str c str    will take  Theta  n  time to find the end of the string  Style  It s good to prefer the C   versions of functions to the C versions unless there s a specific reason to do so otherwise  This is why  for example  it s usually considered better to use std  sort over qsort or std  lower bound over bsearch  unless some other factors come into play that would affect performance    The only reason I could think of where strlen would be useful is if you had a C  -style string that had embedded null characters and you wanted to determine how many characters appeared before the first of them   That s one way in which strlen differs from string  length  the former stops at a null terminator  and the latter counts all the characters in the string   But if that s the case  just use string  find   size t index   str find 0   if  index    str  npos  index   str length    std  cout  lt  lt  index  lt  lt  std  endl    Hope this helps

User · Answer

include lt iostream gt   include lt conio h gt   include lt string h gt  using namespace std  int main          char str 80        int i       cout lt  lt   n enter string         cin getline str 80        int n strlen str        cout lt  lt   n lenght is   lt  lt n       getch         return 0       This is the program if you want to use strlen   Hope this helps

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Manually   int strlen string s        int len   0       while  s len           len         return len

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Function strlen shows the number of character before  0 and using it for std  string may report wrong length   strlen str c str        It may return wrong length    In C    a string can contain  0 within the characters but C-style-zero-terminated strings can not but at the end  If the std  string has a  0 before the last character then strlen reports a length less than the actual length   Try to use  length   or  size    I prefer second one since another standard containers have it   str size

[c++] How to get length of a string using strlen function

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