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71+ < header data-kunai-mdinfo ="{"meta": {"header": ["cstdio"], "id-type": ["type-alias"], "namespace": ["std"]}, "sources": [{"id": "dd2b8f897b18327c261e72866a4a922a625889c6", "source": "#include <cstdio>\n\nint main() {\n std::FILE *file = std::fopen(\"sample.txt\", \"r\");\n if (!file) {\n std::perror(\"\u30d5\u30a1\u30a4\u30eb\u3092\u958b\u3051\u307e\u305b\u3093\u3067\u3057\u305f\");\n return 1;\n }\n\n std::fpos_t pos;\n std::fgetpos(file, &pos); // \u30d5\u30a1\u30a4\u30eb\u306e\u4f4d\u7f6e\u3092pos\u306b\u4fdd\u5b58\u3059\u308b\n\n int c = std::fgetc(file);\n std::printf(\"1\u6587\u5b57\u76ee: %c\\n\", c);\n\n std::fsetpos(file, &pos); // \u30d5\u30a1\u30a4\u30eb\u306e\u8aad\u307f\u53d6\u308a\u4f4d\u7f6e\u3092pos\u306b\u3059\u308b\n\n c = std::fgetc(file);\n std::printf(\"\u3082\u3046\u4e00\u5ea61\u6587\u5b57\u76ee: %c\\n\", c);\n\n std::fclose(file);\n return 0;\n}\n\n"}], "page_id": ["reference", "cstdio", "fpos_t"]} ">
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174+ < span itemprop ="name "> fpos_t</ span >
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188+
189+ < p class ="text-right "> < small >
190+ 最終更新日時(UTC):
191+ < span itemprop ="datePublished " content ="2025-07-16T01:21:38 ">
192+ 2025年07月16日 01時21分38秒
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196+ < span itemprop ="name "> rotarymars</ span >
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198+ が更新
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204+ < span class ="fa fa-fw fa-clock-o fa-flip-horizontal "> </ span > 履歴
205+ </ a >
206+ < a class ="edit " target ="_blank " href ="https://github.com/cpprefjp/site/edit/master/reference/cstdio/fpos_t.md ">
207+ < span class ="fa fa-fw fa-pencil "> </ span > 編集
208+ </ a >
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211+ </ div >
212+ < div class ="row ">
213+ < div class ="col-sm-12 content-body ">
214+
215+ < div class ="identifier-type "> type-alias</ div > < div class ="header "> <cstdio></ div > < h1 itemprop ="name "> < span class ="namespace " title ="namespace std "> std::</ span > < span class ="token "> fpos_t</ span > </ h1 >
216+ < div itemprop ="articleBody "> < p > < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="k "> namespace</ span > < span class ="n "> std</ span > < span class ="p "> {</ span >
217+ < span class ="k "> using</ span > < span class ="kt "> fpos_t</ span > < span class ="o "> =</ span > < span class ="n "> < i > object-type</ i > </ span > < span class ="p "> ;</ span >
218+ < span class ="p "> }</ span >
219+ </ code > </ pre > </ div >
220+ </ p >
221+ < h2 > 概要</ h2 >
222+ < p > ファイルの位置を保持するための型。</ p >
223+ < p > < code > < span href ="https://cpprefjp.github.io/reference/cstdio/fgetpos.md.nolink "> fgetpos()</ span > </ code > 関数や< code > < span href ="https://cpprefjp.github.io/reference/cstdio/fsetpos.md.nolink "> fsetpos()</ span > </ code > 関数で用いられる。これらの関数は< code > < span href ="https://cpprefjp.github.io/reference/cstdio/fseek.md.nolink "> fseek()</ span > </ code > 関数や< code > < span href ="https://cpprefjp.github.io/reference/cstdio/ftell.md.nolink "> ftell()</ span > </ code > 関数と違い、巨大なファイルやマルチバイトファイルに対しても適切に動作するすることを目的に設計された。</ p >
224+ < h2 > 例</ h2 >
225+ < p > < div class ="yata " id ="dd2b8f897b18327c261e72866a4a922a625889c6 "> < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="cp "> #include</ span > < span class ="cpf "> < a href ="../cstdio.html "> <cstdio></ a > </ span > < span class ="cp "> </ span >
226+
227+ < span class ="kt "> int</ span > < span class ="nf "> main</ span > < span class ="p "> ()</ span > < span class ="p "> {</ span >
228+ < span class ="n "> std</ span > < span class ="o "> ::</ span > < span class ="kt "> FILE</ span > < span class ="o "> *</ span > < span class ="n "> file</ span > < span class ="o "> =</ span > < span class ="n "> < a href ="fopen.html "> std::fopen</ a > </ span > < span class ="p "> (</ span > < span class ="s "> "sample.txt"</ span > < span class ="p "> ,</ span > < span class ="s "> "r"</ span > < span class ="p "> );</ span >
229+ < span class ="k "> if</ span > < span class ="p "> (</ span > < span class ="o "> !</ span > < span class ="n "> file</ span > < span class ="p "> )</ span > < span class ="p "> {</ span >
230+ < span class ="n "> < span href ="https://cpprefjp.github.io/reference/cstdio/perror.md.nolink "> std::perror</ span > </ span > < span class ="p "> (</ span > < span class ="s "> "ファイルを開けませんでした"</ span > < span class ="p "> );</ span >
231+ < span class ="k "> return</ span > < span class ="mi "> 1</ span > < span class ="p "> ;</ span >
232+ < span class ="p "> }</ span >
233+
234+ < span class ="n "> < span style ="color:#ff0000 "> std::fpos_t</ span > </ span > < span class ="n "> pos</ span > < span class ="p "> ;</ span >
235+ < span class ="n "> < span href ="https://cpprefjp.github.io/reference/cstdio/fgetpos.md.nolink "> std::fgetpos</ span > </ span > < span class ="p "> (</ span > < span class ="n "> file</ span > < span class ="p "> ,</ span > < span class ="o "> &</ span > < span class ="n "> pos</ span > < span class ="p "> );</ span > < span class ="c1 "> // ファイルの位置をposに保存する</ span >
236+
237+ < span class ="kt "> int</ span > < span class ="n "> c</ span > < span class ="o "> =</ span > < span class ="n "> < a href ="fgetc.html "> std::fgetc</ a > </ span > < span class ="p "> (</ span > < span class ="n "> file</ span > < span class ="p "> );</ span >
238+ < span class ="n "> < a href ="printf.html "> std::printf</ a > </ span > < span class ="p "> (</ span > < span class ="s "> "1文字目: %c</ span > < span class ="se "> \n</ span > < span class ="s "> "</ span > < span class ="p "> ,</ span > < span class ="n "> c</ span > < span class ="p "> );</ span >
239+
240+ < span class ="n "> < span href ="https://cpprefjp.github.io/reference/cstdio/fsetpos.md.nolink "> std::fsetpos</ span > </ span > < span class ="p "> (</ span > < span class ="n "> file</ span > < span class ="p "> ,</ span > < span class ="o "> &</ span > < span class ="n "> pos</ span > < span class ="p "> );</ span > < span class ="c1 "> // ファイルの読み取り位置をposにする</ span >
241+
242+ < span class ="n "> c</ span > < span class ="o "> =</ span > < span class ="n "> < a href ="fgetc.html "> std::fgetc</ a > </ span > < span class ="p "> (</ span > < span class ="n "> file</ span > < span class ="p "> );</ span >
243+ < span class ="n "> < a href ="printf.html "> std::printf</ a > </ span > < span class ="p "> (</ span > < span class ="s "> "もう一度1文字目: %c</ span > < span class ="se "> \n</ span > < span class ="s "> "</ span > < span class ="p "> ,</ span > < span class ="n "> c</ span > < span class ="p "> );</ span >
244+
245+ < span class ="n "> < a href ="fclose.html "> std::fclose</ a > </ span > < span class ="p "> (</ span > < span class ="n "> file</ span > < span class ="p "> );</ span >
246+ < span class ="k "> return</ span > < span class ="mi "> 0</ span > < span class ="p "> ;</ span >
247+ < span class ="p "> }</ span >
248+ </ code > </ pre > </ div >
249+ </ div > </ p >
250+ < h3 > ファイル内容(sample.txt)</ h3 >
251+ < p > < pre > < code > Hello, World!
252+ </ code > </ pre > </ p >
253+ < h3 > 出力</ h3 >
254+ < p > < pre > < code > 1文字目: H
255+ もう一度1文字目: H
256+ </ code > </ pre > </ p >
257+ < h2 > 処理系</ h2 >
258+ < ul >
259+ < li > < a href ="../../implementation.html#clang "> Clang</ a > : ??</ li >
260+ < li > < a href ="../../implementation.html#gcc "> GCC</ a > : ??</ li >
261+ < li > < a href ="../../implementation.html#visual_cpp "> Visual C++</ a > : ??</ li >
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263+
264+ </ div >
265+ </ div >
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