The C-STL - string.h does provide many functions which are often needed when working with strings.
However, the well-known trim operation is not implemented.

As you probably know is trim or sometimes called strip a common string manipulation function which removes leading and trailing whitespace from a string.

There is no standard trim function in C or C++. Most of the available string libraries for C contain code which implements trimming, or functions that significantly ease an efficient implementation. The function has also often been called EatWhitespace in some, non-standard C libraries.

The open source C++ library Boost has several trim variants. One is:

#include <boost/algorithm/string/trim.hpp>
 
trimmed = boost::algorithm::trim_copy(''string'');

MFC provides a Trim() (which makes problems with VC6) and TrimLeft() / TrimRight() as well.

If you simply need a trim function and not a whole library to be included you can use this.

std::string trim(const std::string& s,const std::string& drop = " ")
{
 std::string::size_type first = s.find_first_not_of( drop );
 std::string::size_type last  = s.find_last_not_of( drop );
 
 if( first == std::string::npos || last == std::string::npos ) return std::string( "" );
   return s.substr( first, last - first + 1 );
}

In addition to string.hI have one more solution for you if you’re being willed using std::string (which doesn’t make much sense in most cases).

Remove whitespaces on the right side:

char* trim_right(char* szSource)
{
  char* pszEOS = 0;
 
  // Set pointer to character before terminating NULL
  pszEOS = szSource + strlen( szSource ) - 1;
 
  // iterate backwards until non ' ' is found
  while( (pszEOS >= szSource) && (*pszEOS == ' ') )
    *pszEOS-- = '\0';
  return szSource;
}

Cut off the left side:

char* trim_left(char* szSource)
{
  char* pszBOS = 0;
 
  pszBOS = szSource;
 
   // iterate backwards until non ' ' is found
   while(*pszBOS == ' ')
    *pszBOS++;
 
  return pszBOS;
}

Trim both sides:

char* trim(char *szSource)
{
  return trim_left( trim_right( trim_left(szSource) ) );
}

You also can use it with std::string when converting the std::string with c_str() method.

Trim function is very useful together with substring.