Removing leading and trailing spaces from a string

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How to remove spaces from a string object in C++. For example, how to remove leading and trailing spaces from the below string object.

//Original string: "         This is a sample string                    "
//Desired string: "This is a sample string"

The string class, as far as I know, doesn't provide any methods to remove leading and trailing spaces.

To add to the problem, how to extend this formatting to process extra spaces between words of the string. For example,

// Original string: "          This       is         a sample   string    " 
// Desired string:  "This is a sample string"  

Using the string methods mentioned in the solution, I can think of doing these operations in two steps.

  1. Remove leading and trailing spaces.
  2. Use find_first_of, find_last_of, find_first_not_of, find_last_not_of and substr, repeatedly at word boundaries to get desired formatting.

This is called trimming. If you can use Boost, I'd recommend it.

Otherwise, use find_first_not_of to get the index of the first non-whitespace character, then find_last_not_of to get the index from the end that isn't whitespace. With these, use substr to get the sub-string with no surrounding whitespace.

In response to your edit, I don't know the term but I'd guess something along the lines of "reduce", so that's what I called it. :) (Note, I've changed the white-space to be a parameter, for flexibility)

#include <iostream>
#include <string>

std::string trim(const std::string& str,
                 const std::string& whitespace = " \t")
{
    const auto strBegin = str.find_first_not_of(whitespace);
    if (strBegin == std::string::npos)
        return ""; // no content

    const auto strEnd = str.find_last_not_of(whitespace);
    const auto strRange = strEnd - strBegin + 1;

    return str.substr(strBegin, strRange);
}

std::string reduce(const std::string& str,
                   const std::string& fill = " ",
                   const std::string& whitespace = " \t")
{
    // trim first
    auto result = trim(str, whitespace);

    // replace sub ranges
    auto beginSpace = result.find_first_of(whitespace);
    while (beginSpace != std::string::npos)
    {
        const auto endSpace = result.find_first_not_of(whitespace, beginSpace);
        const auto range = endSpace - beginSpace;

        result.replace(beginSpace, range, fill);

        const auto newStart = beginSpace + fill.length();
        beginSpace = result.find_first_of(whitespace, newStart);
    }

    return result;
}

int main(void)
{
    const std::string foo = "    too much\t   \tspace\t\t\t  ";
    const std::string bar = "one\ntwo";

    std::cout << "[" << trim(foo) << "]" << std::endl;
    std::cout << "[" << reduce(foo) << "]" << std::endl;
    std::cout << "[" << reduce(foo, "-") << "]" << std::endl;

    std::cout << "[" << trim(bar) << "]" << std::endl;
}

Result:

[too much               space]  
[too much space]  
[too-much-space]  
[one  
two]  

Trim (Remove leading and trailing spaces) a string in Java , To remove leading and trailing spaces in Java, use the trim() method. This method returns a copy of this string with leading and trailing white  For example, how to remove leading and trailing spaces from the below string object. //Original string: " This is a sample string " //Desired string: "This is a sample string" The string class, as far as I know, doesn't provide any methods to remove leading and trailing spaces.

Easy removing leading, trailing and extra spaces from a std::string in one line

value = std::regex_replace(value, std::regex("^ +| +$|( ) +"), "$1");

removing only leading spaces

value.erase(value.begin(), std::find_if(value.begin(), value.end(), std::bind1st(std::not_equal_to<char>(), ' ')));

or

value = std::regex_replace(value, std::regex("^ +"), "");

removing only trailing spaces

value.erase(std::find_if(value.rbegin(), value.rend(), std::bind1st(std::not_equal_to<char>(), ' ')).base(), value.end());

or

value = std::regex_replace(value, std::regex(" +$"), "");

removing only extra spaces

value = regex_replace(value, std::regex(" +"), " ");

Trim a string in Java to remove leading and trailing spaces, Which method removes trailing and leading Whitespaces in a string? The TRIM function is fully automatic. It removes removes both leading and trailing spaces from text, and also "normalizes" multiple spaces between words to one space character only. All you need to do is supply a reference to a cell. TRIM with CLEAN. If you also need to remove line breaks from cells, you can add the CLEAN function like so:

I am currently using these functions:

// trim from left
inline std::string& ltrim(std::string& s, const char* t = " \t\n\r\f\v")
{
    s.erase(0, s.find_first_not_of(t));
    return s;
}

// trim from right
inline std::string& rtrim(std::string& s, const char* t = " \t\n\r\f\v")
{
    s.erase(s.find_last_not_of(t) + 1);
    return s;
}

// trim from left & right
inline std::string& trim(std::string& s, const char* t = " \t\n\r\f\v")
{
    return ltrim(rtrim(s, t), t);
}

// copying versions

inline std::string ltrim_copy(std::string s, const char* t = " \t\n\r\f\v")
{
    return ltrim(s, t);
}

inline std::string rtrim_copy(std::string s, const char* t = " \t\n\r\f\v")
{
    return rtrim(s, t);
}

inline std::string trim_copy(std::string s, const char* t = " \t\n\r\f\v")
{
    return trim(s, t);
}

How to remove leading and trailing whitespace from the string in , How do you remove leading and trailing spaces in Java? You can use the STRIP function to remove both the leading and trailing spaces from the character strings. Example

Boost string trim algorithm

#include <boost/algorithm/string/trim.hpp>

[...]

std::string msg = "   some text  with spaces  ";
boost::algorithm::trim(msg);

what is meant by trailing space and what's the difference between it , How can you trim whitespace characters from the beginning or end of a string? To remove leading and trailing spaces from text string in Cells, you can use the TRIM function to remove extra spaces. So you can type the following formula in Cell B1, then press Enter key. =TRIM(A1) Then select Cell B1 and drag the AutoFill Handle down to other cells that you want to remove the leading or trailing spaces.

Here is how you can do it:

std::string & trim(std::string & str)
{
   return ltrim(rtrim(str));
}

And the supportive functions are implemeted as:

std::string & ltrim(std::string & str)
{
  auto it2 =  std::find_if( str.begin() , str.end() , [](char ch){ return !std::isspace<char>(ch , std::locale::classic() ) ; } );
  str.erase( str.begin() , it2);
  return str;   
}

std::string & rtrim(std::string & str)
{
  auto it1 =  std::find_if( str.rbegin() , str.rend() , [](char ch){ return !std::isspace<char>(ch , std::locale::classic() ) ; } );
  str.erase( it1.base() , str.end() );
  return str;   
}

And once you've all these in place, you can write this as well:

std::string trim_copy(std::string const & str)
{
   auto s = str;
   return ltrim(rtrim(s));
}

Try this

C# String Trim Method (TrimStart, TrimEnd), s.trim(). see String#trim(). Without any internal method, use regex like s.replaceAll​("^\\s+", "").replaceAll("\\s+$", ""). or s.replaceAll("^\\s+|\\s+$",  With Java-11 and above, you can make use of the String.strip API to return a string whose value is this string, with all leading and trailing whitespace removed. The javadoc for the same reads : /** * Returns a string whose value is this string, with all leading * and trailing {@link Character#isWhitespace(int) white space} * removed.

Java remove leading whitespaces from String, 2. Java program to remove leading and trailing spaces. If you want to remove surrounding whitespaces from string, then best way is to use String.trim() method. Another option is to use the stri_trim function from the stringi package which defaults to removing leading and trailing whitespace: > x <- c(" leading space","trailing space ") > stri_trim(x) [1] "leading space" "trailing space" For only removing leading whitespace, use stri_trim_left. For only removing trailing whitespace, use stri_trim_right.

Remove leading and trailing whitespace from strings, For example, strtrim removes leading and trailing space and tab characters, but does not remove the nonbreaking space character, char(160) . Examples. collapse  Required knowledge. Basic C programming, Loop, String, Function. Must know - Program to remove element from array Logic to remove leading and trailing white spaces. In my previous posts, I already explained how to remove leading as well as trailing white space characters from a given string.

How do I remove leading and trailing spaces from a string , How do I remove leading and trailing spaces from Learn more about strtok, deblank, remove, leading, trailing, spaces, trim, string MATLAB. newStr = strtrim (str) removes leading and trailing whitespace characters from str and returns the result as newStr. However, strtrim does not remove significant whitespace characters. For example, strtrim removes leading and trailing space and tab characters, but does not remove the nonbreaking space character, char (160).

Comments
  • i assume you meant 'size_t'. and you've got an off-by-one on the substring, should be substr(beginStr, endStr - beginStr + 1);
  • Should site_t be size_t? And I think where you have the comment no whitespace means the string is all whitespace or empty.
  • Thanks, fixed the size_t typo and off-by-one in the edit, but didn't notice my comment was inverted, thanks.
  • @GMan very elegant solution. Thanks.
  • Bug: try running "one\ttwo" thru trim(). Result is an empty string. You need to also test endStr against std::string::npos.
  • Nice one. It would be useful to provide some info on what is happening here, as it is difficult to understand these codes.
  • Works only in C++11, though.
  • It does not remove tabs but this can be fixed. What cannot be fixed is that it's terribly slow (~100 times slower than answers with substr or erase).
  • for speed optimization regex is not the optimal solution, but it could be improved by creating an instance of regex once
  • Peoples won't like looking into 10 pages of code to learn how to trim a string.
  • it is broken if the string only has spaces
  • ...and you avoided bringing in 2M of header files into your build!