{"id":8390,"date":"2024-03-14T08:02:00","date_gmt":"2024-03-14T08:02:00","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-read-a-file-from-a-specified-line-in-c-using-fread\/"},"modified":"2025-08-03T04:14:24","modified_gmt":"2025-08-03T04:14:24","slug":"how-to-read-a-file-from-a-specified-line-in-c-using-fread","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-read-a-file-from-a-specified-line-in-c-using-fread\/","title":{"rendered":"Read File from Line in C++ Using fread"},"content":{"rendered":"<p>In C++, the fread function is used to read data from a file, specifically for reading binary files. If you need to read from a specific line in the file, you can first locate the position of that line and then call the fread function to perform the reading operation.<\/p>\n<p>Here is a simple example code that demonstrates how to read file contents from a specified line:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;iostream&gt;<\/span><\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;fstream&gt;<\/span><\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;cstring&gt;<\/span><\/span>\r\n\r\n<span class=\"hljs-keyword\">using<\/span> <span class=\"hljs-keyword\">namespace<\/span> std;\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-type\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n    <span class=\"hljs-function\">ifstream <span class=\"hljs-title\">file<\/span><span class=\"hljs-params\">(<span class=\"hljs-string\">\"example.txt\"<\/span>, ios::binary)<\/span><\/span>; <span class=\"hljs-comment\">\/\/ \u6253\u5f00\u6587\u4ef6<\/span>\r\n\r\n    <span class=\"hljs-keyword\">if<\/span> (!file.<span class=\"hljs-built_in\">is_open<\/span>()) {\r\n        cout &lt;&lt; <span class=\"hljs-string\">\"\u65e0\u6cd5\u6253\u5f00\u6587\u4ef6!\"<\/span> &lt;&lt; endl;\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">1<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-type\">int<\/span> line = <span class=\"hljs-number\">3<\/span>;   <span class=\"hljs-comment\">\/\/ \u6307\u5b9a\u8981\u8bfb\u53d6\u7684\u884c\u6570<\/span>\r\n    <span class=\"hljs-type\">int<\/span> lineSize = <span class=\"hljs-number\">256<\/span>; <span class=\"hljs-comment\">\/\/ \u5047\u8bbe\u6bcf\u884c\u6700\u5927\u957f\u5ea6\u4e0d\u8d85\u8fc7256\u4e2a\u5b57\u7b26<\/span>\r\n\r\n    file.<span class=\"hljs-built_in\">seekg<\/span>(<span class=\"hljs-number\">0<\/span>, ios::beg); <span class=\"hljs-comment\">\/\/ \u5c06\u6587\u4ef6\u6307\u9488\u5b9a\u4f4d\u5230\u6587\u4ef6\u5f00\u5934<\/span>\r\n\r\n    <span class=\"hljs-keyword\">for<\/span> (<span class=\"hljs-type\">int<\/span> i = <span class=\"hljs-number\">1<\/span>; i &lt; line; i++) {\r\n        file.<span class=\"hljs-built_in\">ignore<\/span>(lineSize, <span class=\"hljs-string\">'\\n'<\/span>); <span class=\"hljs-comment\">\/\/ \u5ffd\u7565\u524d\u9762\u7684\u884c<\/span>\r\n    }\r\n\r\n    <span class=\"hljs-type\">char<\/span> buffer[lineSize];\r\n    file.<span class=\"hljs-built_in\">read<\/span>(buffer, lineSize); <span class=\"hljs-comment\">\/\/ \u8bfb\u53d6\u6307\u5b9a\u884c\u7684\u5185\u5bb9<\/span>\r\n\r\n    cout &lt;&lt; <span class=\"hljs-string\">\"\u7b2c\"<\/span> &lt;&lt; line &lt;&lt; <span class=\"hljs-string\">\"\u884c\u7684\u5185\u5bb9\u662f\uff1a\"<\/span> &lt;&lt; buffer &lt;&lt; endl;\r\n\r\n    file.<span class=\"hljs-built_in\">close<\/span>(); <span class=\"hljs-comment\">\/\/ \u5173\u95ed\u6587\u4ef6<\/span>\r\n\r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">0<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>In the example above, we opened a text file named example.txt first, then positioned the file pointer to the beginning of the file using the seekg function. Next, we skipped the previous lines using the ignore function, finally, we read the content of the specified line using the read function and output it to the console.<\/p>\n<p>Please note that the variable lineSize in the above code represents the maximum length of each line, and should be adjusted according to actual requirements. Additionally, the above example is only applicable for text files. If you need to read binary files, you can set the open mode of ifstream to ios::binary.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C++, the fread function is used to read data from a file, specifically for reading binary files. If you need to read from a specific line in the file, you can first locate the position of that line and then call the fread function to perform the reading operation. Here is a simple example [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[11278,7132,11273,381,11274],"class_list":["post-8390","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-binary-file-operations","tag-c-file-i-o","tag-c-file-reading","tag-c-programming","tag-fread-function"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Read File from Line in C++ Using fread - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to read from a specific line in a file using C++ fread function. Includes code examples for efficient file reading operations.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/blog\/how-to-read-a-file-from-a-specified-line-in-c-using-fread\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Read File from Line in C++ Using fread\" \/>\n<meta property=\"og:description\" content=\"Learn how to read from a specific line in a file using C++ fread function. 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