很多其他语言的libary都会有去除string类的首尾空格的库函数，但是标准C++的库却不提供这个功能。但是C++string也提供很强大的功能，实现trim这种功能也不难。下面是几种方法：
1.使用string的find_first_not_of,和find_last_not_of方法
[cpp] view plaincopy
<EMBED id=ZeroClipboardMovie_1 height=18 name=ZeroClipboardMovie_1 type=application/x-shockwave-flash align=middle pluginspage=http://www.macromedia.com/go/getflashplayer width=18 src=http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf wmode="transparent" flashvars="id=1&width=18&height=18" allowfullscreen="false" allowscriptaccess="always" bgcolor="#ffffff" quality="best" menu="false" loop="false">
/*
Filename : StringTrim1.cpp
Compiler : Visual C++ 8.0
Description : Demo how to trim string by find_first_not_of & find_last_not_of
Release : 11/17/2006
*/
#include <iostream>
#include <string>
std::string& trim(std::string &);
int main()
{
std::string s = " Hello World!! ";
std::cout << s << " size:" << s.size() << std::endl;
std::cout << trim(s) << " size:" << trim(s).size() << std::endl;
return 0;
}
std::string& trim(std::string &s)
{
if (s.empty())
{
return s;
}
s.erase(0,s.find_first_not_of(" "));
s.erase(s.find_last_not_of(" ") + 1);
return s;
}
2.使用boost库中的trim,boost库对提供很多C++标准库没有但是又非常常用和好用的库函数，例如正则表达式，线程库等等。
[cpp] view plaincopy
<EMBED id=ZeroClipboardMovie_2 height=18 name=ZeroClipboardMovie_2 type=application/x-shockwave-flash align=middle pluginspage=http://www.macromedia.com/go/getflashplayer width=18 src=http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf wmode="transparent" flashvars="id=2&width=18&height=18" allowfullscreen="false" allowscriptaccess="always" bgcolor="#ffffff" quality="best" menu="false" loop="false">
/*
Filename : boostStringTrim.cpp
Compiler : Visual C++ 8.0 / ISO C++ (boost)
Description : Demo how to boost to trim string
Release : 02/22/2007 1.0
*/
#include <iostream>
#include <string>
#include <boost/algorithm/string.hpp>
using namespace std;
using namespace boost;
int main() {
string s = " hello boost!! ";
trim(s);
cout << s << endl;
}
3.使用template（我用GCC编译不通过，用VS2005却可以）
[cpp] view plaincopy
<EMBED id=ZeroClipboardMovie_3 height=18 name=ZeroClipboardMovie_3 type=application/x-shockwave-flash align=middle pluginspage=http://www.macromedia.com/go/getflashplayer width=18 src=http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf wmode="transparent" flashvars="id=3&width=18&height=18" allowfullscreen="false" allowscriptaccess="always" bgcolor="#ffffff" quality="best" menu="false" loop="false">
/*
Filename : stringTrim1.cpp
Compiler : Visual C++ 8.0
Description : Demo how to trim string by other method.
Release : 11/18/2006
*/
#include <string>
#include <iostream>
#include <cwctype>
template <class T>
std::basic_string<T>& trim(std::basic_string<T>&);
int main( )
{
std::string s = " Hello World!! ";
std::cout << s << " size:" << s.size() << std::endl;
std::cout << trim(s) << " size:" << trim(s).size() << std::endl;
return 0;
}
template <class T>
std::basic_string<T>& trim(std::basic_string<T>& s)
{
if (s.empty()) {
return s;
}
std::basic_string<T>::iterator c;
// Erase whitespace before the string
for (c = s.begin(); c != s.end() && iswspace(*c++);); s.erase(s.begin(), --c);
// Erase whitespace after the string
for (c = s.end(); c != s.begin() && iswspace(*--c);); s.erase(++c, s.end());
return s;
}
split方法
[cpp] view plaincopy
<EMBED id=ZeroClipboardMovie_4 height=18 name=ZeroClipboardMovie_4 type=application/x-shockwave-flash align=middle pluginspage=http://www.macromedia.com/go/getflashplayer width=18 src=http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf wmode="transparent" flashvars="id=4&width=18&height=18" allowfullscreen="false" allowscriptaccess="always" bgcolor="#ffffff" quality="best" menu="false" loop="false">
//注意：当字符串为空时，也会返回一个空字符串
void split(std::string& s, std::string& delim,std::vector< std::string >* ret)
{
size_t last = 0;
size_t index=s.find_first_of(delim,last);
while (index!=std::string::npos)
{
ret->push_back(s.substr(last,index-last));
last=index+1;
index=s.find_first_of(delim,last);
}
if (index-last>0)
{
ret->push_back(s.substr(last,index-last));
}
}
来源：oschina
链接：https://my.oschina.net/u/1777508/blog/489196