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Table of Contents
Create and initialize strings
String stitching and comparison
Access and modify content
Find and clean common operations
Home Backend Development C++ How to use std::string in C ?

How to use std::string in C ?

Jul 13, 2025 am 01:34 AM

<p>std::string is the preferred way to handle strings in C, which is safer and easier to use than character arrays. 1. The creation methods include direct assignment, constructor initialization, copying and repeating character construction; 2. Supports styling and dictionary comparison; 3. Characters can be accessed through subscripts or .at(), and supports modification, replacement, insertion and extraction of substrings; 4. Provides search methods such as .find() and .rfind(), as well as common operations such as obtaining length, judging empty content, and clearing content. Mastering these basic usages allows you to flexibly use std::string in most projects. </p> <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175234169126895.jpg" class="lazy" alt="How to use std::string in C ?"></p> <p> <code>std::string</code> is the most commonly used way to process strings in C. It is safer and easier to use than traditional character arrays (char[]), and supports many convenient operations. If you are just starting to learn C, it is very necessary to master the basic usage of <code>std::string</code> . </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175234169262253.jpeg" class="lazy" alt="How to use std::string in C ?"><h2 id="Create-and-initialize-strings"> Create and initialize strings</h2> <p> Before using <code>std::string</code> , you need to include the header file <code><string></string></code> : </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175234169470954.jpeg" class="lazy" alt="How to use std::string in C ?"><pre class='brush:php;toolbar:false;'> #include <string></pre><p> Creating a string is very simple, you can directly assign values or initialize them through a constructor:</p><ul><li> Empty string: <code>std::string s;</code></li><li> String with initial value: <code>std::string s = "hello";</code></li><li> Copy from another string: <code>std::string s2(s);</code></li><li> Repeat character construction: <code>std::string s(5, &#39;a&#39;);</code> This will generate <code>"aaaaa"</code></li></ul><p> These methods are very intuitive, and beginners recommend starting with direct assignment. </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175234169573366.jpeg" class="lazy" alt="How to use std::string in C ?" /><h2 id="String-stitching-and-comparison"> String stitching and comparison</h2><p> <code>std::string</code> supports common operator overloading, such as<code> </code>and <code>=</code> to splice strings:</p><pre class='brush:php;toolbar:false;'> std::string a = "Hello"; std::string b = " world"; a = b; // a becomes "Hello world"</pre><p> Note that you should be careful when splicing different types. For example, you cannot directly add <code>int</code> to a string, you must first convert it into a string form.</p><p> String comparison is also very convenient. You can use <code>==</code> , <code>!=</code> , <code><</code> , <code>></code> and other operators for dictionary order comparison:</p><pre class='brush:php;toolbar:false;'> if (s1 < s2) { // s1 is less than s2 in dictionary order }</pre><p> This is useful for sorting or judging whether the input is as expected.</p><h2 id="Access-and-modify-content"> Access and modify content</h2><p> Characters can be accessed through subscripts, or <code>.at()</code> method can be used, which throws an exception when it is crossed:</p><pre class='brush:php;toolbar:false;'> std::string s = "abc"; char c1 = s[0]; // &#39;a&#39; char c2 = s.at(1); // &#39;b&#39;</pre><p> The modification content is similar:</p><ul><li> Modify a single character: <code>s[0] = &#39;A&#39;;</code></li><li> Replace substring: <code>s.replace(0, 3, "XYZ");</code> replace the first three characters with XYZ</li><li> Insert character: <code>s.insert(2, "xx");</code></li></ul><p> You can also use <code>.substr(pos, len)</code> to extract substrings:</p><pre class='brush:php;toolbar:false;'> std::string sub = s.substr(2, 3); // Take 3 characters from position 2</pre><p> This function is very practical when parsing text and extracting key information.</p><h2 id="Find-and-clean-common-operations"> Find and clean common operations</h2><p> To find out whether there is a character or substring in a string, you can use the following method:</p><ul><li> <code>.find("abc")</code> : Returns the first occurrence location, and cannot find it to return <code>std::string::npos</code></li><li> <code>.rfind()</code> : Find from behind to front</li><li> <code>.find_first_of()</code> : Find any matching character</li></ul><p> For example:</p><pre class='brush:php;toolbar:false;'> size_t pos = s.find("world"); if (pos != std::string::npos) { // Found}</pre><p> There are also some commonly used helper functions:</p> <ul> <li> <code>.length()</code> or <code>.size()</code> : Get the length</li> <li> <code>.empty()</code> : determines whether it is empty</li> <li> <code>.clear()</code> : Clear string content</li> </ul> <p> Although these operations are small, they are often used in daily development.</p> <p> Basically that's it. With these basic operations mastered, you can use <code>std::string</code> flexibly in most projects.</p>

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