{"id":1006,"date":"2021-03-26T10:40:19","date_gmt":"2021-03-26T02:40:19","guid":{"rendered":"http:\/\/www.mustenaka.cn\/?p=1006"},"modified":"2021-03-26T10:40:19","modified_gmt":"2021-03-26T02:40:19","slug":"occopystdout","status":"publish","type":"post","link":"https:\/\/www.mustenaka.cn\/index.php\/2021\/03\/26\/occopystdout\/","title":{"rendered":"OC\u4f18\u96c5\u7684\u5b9e\u73b0\u5c06\u7ec8\u7aef\u6570\u636e\u7ed9\u590d\u5236\u5230\u6587\u4ef6\u7684\u65b9\u6cd5\uff08\u4e0d\u662f\u6bcf\u4e00\u4e2a\u8f93\u51fa\u90fd\u5728\u65c1\u8fb9\u5199\u4e00\u4e2a\u8f93\u5165\u6307\u5b9a\u6587\u4ef6\uff09"},"content":{"rendered":"<h3>OC \u65e5\u5fd7<\/h3>\n<p>\u5728\u672c\u9879\u76ee\u4e2d\uff0c\u60f3\u8981\u5b9e\u73b0\u4e00\u7c7b\u529f\u80fd\uff0c\u5373\u542f\u52a8\u540e\uff0c\u4e00\u5207\u8f93\u5165\u8f93\u51fa\u6d41\u5305\u62ec\u9519\u8bef\u6d41\u5168\u90e8\u81ea\u52a8\u7684\u5199\u5165\u5230\u4e00\u4e2a\u6587\u4ef6\u4e2d\uff0c\u5728\u767e\u5ea6\u4e86\u5404\u79cdOC\u7684\u65b9\u6cd5\uff0c\u57fa\u672c\u4e0a\u90fd\u662f\u8bbe\u7f6e\u5bfc\u51fa\u5230\u4e00\u4e2a\u6307\u5b9a\u76ee\u5f55\uff0c\u7136\u540e\u8c03\u7528C\u8bed\u8a00\u7684freopen\u8fdb\u884c\u91cd\u5b9a\u5411\uff0c\u4f7f\u7528C\u8bed\u8a00\u7684freopen\u91cd\u5b9a\u5411\u548c\u5bf9NSLog\u7684\u91cd\u5b9a\u5411\u8bbe\u7f6e\u65b9\u6cd5\u6709\u4e00\u4e2a\u533a\u522b\uff0c\u5c31\u662ffreopen\u9664\u4e86NSLog\uff0cC\u8bed\u8a00\u7684\u8f93\u51fa\u65b9\u5f0fprintf\u4e5f\u53ef\u4ee5\u505a\u5230\uff0c\u800c\u5728\u4e32\u53e3\u4ea4\u4e92\u7684\u65f6\u5019\uff0c\u7531\u4e8e\u4f20\u9012\u8fdb\u6765\u7684\u76f4\u63a5\u5c31\u662f\u5b57\u7b26\u6d41\uff0c\u56e0\u6b64\u5fc5\u987b\u4f7f\u7528\u7c7b\u4f3cfreopen\u7684\u65b9\u6cd5\u8fdb\u884c\u517c\u5bb9\u64cd\u4f5c\u3002<\/p>\n<p>objective-c<\/p>\n<pre class=\"pure-highlightjs\"><code class=\"\" objectivec=\"\">\/\/OC\u4ee3\u7801\uff0c\u91cd\u5b9a\u5411\uff0c\u5176\u5b9e\u5c31\u662f\u81ea\u5df1\u5904\u7406\u4e86\u4e00\u4e0b\u6587\u4ef6\u8def\u5f84\u7136\u540e\u8c03\u7528\u4e86C\u8bed\u8a00\r\nfreopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding],\"a+\", stdout);<\/code><\/pre>\n<p>\u4f46\u662f\u4e00\u65e6\u8fdb\u884c\u4e86\u91cd\u5b9a\u5411\uff0c\u539f\u672c\u8f93\u51fa\u7ed9\u63a7\u5236\u53f0\u7aef\u7684\u4ea4\u4e92\u663e\u793a\u5c31\u5168\u90e8\u6d88\u5931\u4e86\uff0c\u8fd9\u6837\u5c31\u5c06\u7a0b\u5e8f\u7f16\u7a0b\u4e86\u76f2\u6253\u4e00\u822c\uff0c\u641c\u7d22\u4e86\u534a\u5929\u7531\u4e8e\uff0c\u73b0\u5728\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u505a\u7684\u5982\u4e0b\u7b14\u8bb0\uff1a<\/p>\n<h3>freopen<\/h3>\n<p>\u9996\u5148\u6765\u7ffb\u9605freopen\u7684\u6587\u6863<\/p>\n<pre class=\"pure-highlightjs\"><code class=\"\" cpp=\"\">FILE *freopen(const char *filename, const char *mode, FILE *stream)<\/code><\/pre>\n<p>\u4f20\u5165\u53c2\u6570<span class=\"Apple-tab-span\"> <\/span><\/p>\n<table class=\"md-table\">\n<thead>\n<tr class=\"md-end-block md-focus-container\" cid=\"n11\" mdtype=\"table_row\">\n<th><span class=\"td-span md-focus\" cid=\"n12\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain md-expand\">\u540d\u79f0<\/span><\/span><\/th>\n<th><span class=\"td-span\" cid=\"n13\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">\u89e3\u91ca<\/span><\/span><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr class=\"md-end-block\" cid=\"n14\" mdtype=\"table_row\">\n<td><span class=\"td-span\" cid=\"n15\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">mode<\/span><\/span><\/td>\n<td><span class=\"td-span\" cid=\"n16\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">\u662f\u6587\u4ef6\u7684\u8bbf\u95ee\u6a21\u5f0f\uff0c\u540cfopen()\u51fd\u6570\uff0c\u4e3b\u8981\u6709\u3010&#8221;r&#8221;,&#8221;w&#8221;,&#8221;a&#8221;,&#8221;r+&#8221;,&#8221;w+&#8221;,&#8221;a+&#8221;\u3011\uff0c\u5177\u4f53\u610f\u601d\u4e0d\u505a\u89e3\u91ca<\/span><\/span><\/td>\n<\/tr>\n<tr class=\"md-end-block\" cid=\"n17\" mdtype=\"table_row\">\n<td><span class=\"td-span\" cid=\"n18\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">stream<\/span><\/span><\/td>\n<td><span class=\"td-span\" cid=\"n19\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">\u6307\u5411FILE\u5bf9\u8c61\u7684\u6307\u6b63\uff0c\u8be5FILE\u5bf9\u8c61\u8868\u793a\u4e86\u8981\u88ab\u91cd\u65b0\u6253\u5f00\u7684\u6d41<\/span><\/span><\/td>\n<\/tr>\n<tr class=\"md-end-block md-focus-container\" cid=\"n20\" mdtype=\"table_row\">\n<td><span class=\"td-span\" cid=\"n21\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain\">filename<\/span><\/span><\/td>\n<td><span class=\"td-span md-focus\" cid=\"n22\" mdtype=\"table_cell\"><span md-inline=\"plain\" class=\"md-plain md-expand\">\u662f\u9700\u8981\u6253\u5f00\u4f20\u5165\u7684\u6587\u4ef6\u5730\u5740<\/span><\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3 cid=\"n23\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u4f20\u51fa\u53c2\u6570<\/span><\/h3>\n<p cid=\"n24\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u5982\u679c\u6587\u4ef6\u53ef\u4ee5\u6210\u529f\u6253\u5f00\uff0c\u5219\u51fd\u6570\u8fd4\u56de\u4e00\u4e2a\u6307\u9488\uff0c\u5426\u5219\u8fd4\u56deNULL\u3002<\/span><\/p>\n<p cid=\"n25\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u5176\u5185\u90e8\u5b9e\u73b0\u4ee3\u7801\u4e3a\uff1a<\/span><\/p>\n<pre spellcheck=\"false\" class=\"md-fences md-end-block ty-contain-cm modeLoaded\" lang=\"C\" cid=\"n26\" mdtype=\"fences\"><span role=\"presentation\"><span class=\"cm-variable\">FILE<\/span><span class=\"cm-operator\">*<\/span> <span class=\"cm-def\">Freopen<\/span>(<span class=\"cm-keyword\">const<\/span> <span class=\"cm-variable-3\">char<\/span> <span class=\"cm-variable-3\">*<\/span><span class=\"cm-variable\">fileName<\/span>, <span class=\"cm-keyword\">const<\/span> <span class=\"cm-variable-3\">char<\/span> <span class=\"cm-variable-3\">*<\/span><span class=\"cm-variable\">type<\/span>, <span class=\"cm-variable\">FILE<\/span> <span class=\"cm-operator\">*<\/span><span class=\"cm-variable\">stream<\/span>){<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable\">FILE<\/span> <span class=\"cm-operator\">*<\/span><span class=\"cm-variable\">fileFp<\/span> <span class=\"cm-operator\">=<\/span> <span class=\"cm-variable\">fopen<\/span>(<span class=\"cm-variable\">fileName<\/span>, <span class=\"cm-variable\">type<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">fd1<\/span> <span class=\"cm-operator\">=<\/span> <span class=\"cm-variable\">fileno<\/span>(<span class=\"cm-variable\">fileFp<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">fd2<\/span> <span class=\"cm-operator\">=<\/span> <span class=\"cm-variable\">fileno<\/span>(<span class=\"cm-variable\">stream<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">dup2<\/span>(<span class=\"cm-variable\">fd1<\/span>, <span class=\"cm-variable\">fd2<\/span>) <span class=\"cm-operator\">&lt;<\/span> <span class=\"cm-number\">0<\/span>) <span class=\"cm-keyword\">return<\/span> <span class=\"cm-variable\">NULL<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">else<\/span> <span class=\"cm-keyword\">return<\/span> <span class=\"cm-variable\">stream<\/span>;<\/span>\r\n<span role=\"presentation\">}<\/span><\/pre>\n<p cid=\"n27\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u5229\u7528fileno\u53d6\u51fa\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5bf9\u4e8efileName\u91c7\u7528\u65b0\u521b\u5efa\u7684\u65b9\u6cd5\uff08\u4e5f\u96be\u602a\u9700\u8981\u63d0\u524d\u5224\u65ad\u6587\u4ef6\u662f\u5426\u5b58\u5728\uff0c\u5426\u5219\u5219\u5220\u9664\u6587\u4ef6\u91cd\u65b0\u521b\u5efa\uff09\uff0c\u8fd9\u91cc\u4e3b\u8981\u8c03\u7528\u5230\u4e86dup2\u8fd9\u4e2a\u51fd\u6570\uff0c\u6709\u5173dup\uff0cdup2\u8fd9\u4e24\u4e2a\u51fd\u6570\uff0c\u641c\u7d22\u5230\u7684\u7b14\u8bb0\u53c8\u5982\u4e0b\uff1a<\/span><\/p>\n<h3 cid=\"n28\" mdtype=\"heading\" class=\"md-end-block md-heading\"><span md-inline=\"plain\" class=\"md-plain\">dup<\/span><\/h3>\n<p cid=\"n29\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">dup\u7684\u5b9a\u4e49\u76f8\u5f53\u7b80\u5355<\/span><\/p>\n<pre spellcheck=\"false\" class=\"md-fences md-end-block ty-contain-cm modeLoaded\" lang=\"c\" cid=\"n30\" mdtype=\"fences\"><span role=\"presentation\"><span class=\"cm-variable-3\">int<\/span> <span class=\"cm-def\">dup<\/span>(<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">oldfd<\/span>);<\/span><\/pre>\n<p cid=\"n31\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">dup\u7528\u6765\u590d\u5236\u53c2\u6570oldfd\u6240\u6307\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5f53\u590d\u5236\u6210\u529f\u65f6\uff0c\u8fd4\u56de\u6700\u5c0f\u7684\u5c1a\u672a\u88ab\u4f7f\u7528\u8fc7\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u82e5\u6709\u9519\u8bef\u5219\u8fd4\u56de-1.\u9519\u8bef\u4ee3\u7801\u5b58\u5165errno\u4e2d\u3002\u8fd4\u56de\u7684\u65b0\u6587\u4ef6\u63cf\u8ff0\u7b26\u548c\u53c2\u6570oldfd\u6307\u5411\u540c\u4e00\u4e2a\u6587\u4ef6\uff0c\u8fd9\u4e24\u4e2a\u63cf\u8ff0\u7b26\u5171\u4eab\u540c\u4e00\u4e2a\u6570\u636e\u7ed3\u6784\uff0c\u5171\u4eab\u6240\u6709\u7684\u9501\u5b9a\uff0c\u8bfb\u5199\u6307\u9488\u548c\u5404\u9879\u5168\u73b0\u6216\u6807\u5fd7\u4f4d\u3002<\/span><\/p>\n<p cid=\"n32\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u800c\u8c03\u7528dup\u4e5f\u7b49\u540c\u4e8e\u8c03\u7528fcntl(oldfd, F_DUPFD, 0);\u8fd9\u4e2a\u65b9\u6cd5\uff08\u540e\u9762\u4ecb\u7ecd\uff09\u3002<\/span><\/p>\n<p cid=\"n33\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u4e00\u4e2a\u4ee3\u7801\u793a\u4f8b\u5982\u4e0b\uff1a<\/span><\/p>\n<pre spellcheck=\"false\" class=\"md-fences md-end-block ty-contain-cm modeLoaded\" lang=\"c\" cid=\"n34\" mdtype=\"fences\"><span role=\"presentation\"><span class=\"cm-meta\">#include&lt;stdio.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include&lt;sys\/stat.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include&lt;fcntl.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include&lt;unistd.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-variable-3\">int<\/span> <span class=\"cm-def\">main<\/span>(<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">argc<\/span>, <span class=\"cm-variable-3\">char*<\/span> <span class=\"cm-variable\">argv<\/span>[])<\/span>\r\n<span role=\"presentation\">{<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">fd<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">open<\/span>(<span class=\"cm-string\">\"text.txt\"<\/span>, <span class=\"cm-variable\">O_CREAT<\/span><span class=\"cm-operator\">|<\/span><span class=\"cm-variable\">O_RDWR<\/span><span class=\"cm-operator\">|<\/span><span class=\"cm-variable\">O_TRUNC<\/span>, <span class=\"cm-variable\">S_IRUSR<\/span><span class=\"cm-operator\">|<\/span><span class=\"cm-variable\">S_IWUSR<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">fd<\/span> <span class=\"cm-operator\">&lt;<\/span> <span class=\"cm-number\">0<\/span>)<\/span>\r\n<span role=\"presentation\">\u00a0 {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"Open Error!\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-keyword\">return<\/span> <span class=\"cm-number\">0<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">fd2<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">dup<\/span>(<span class=\"cm-variable\">fd<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">fd2<\/span><span class=\"cm-operator\">&lt;<\/span><span class=\"cm-number\">0<\/span>)<\/span>\r\n<span role=\"presentation\">\u00a0 {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"Error!\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-keyword\">return<\/span> <span class=\"cm-number\">0<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">char<\/span> <span class=\"cm-variable\">buf<\/span>[<span class=\"cm-number\">1000<\/span>];<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">n<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-comment\">\/\/\u63a5\u53d7\u952e\u76d8\u8f93\u5165\uff0c\u5e76\u5c06\u5176\u5b58\u5165buf\u6240\u6307\u5411\u7684\u7f13\u5b58\u4e2d<\/span><\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">while<\/span>((<span class=\"cm-variable\">n<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">read<\/span>(<span class=\"cm-variable\">STDIN_FILENO<\/span>, <span class=\"cm-variable\">buf<\/span>,<span class=\"cm-number\">1000<\/span>)) <span class=\"cm-operator\">&gt;<\/span> <span class=\"cm-number\">0<\/span> ) \u00a0 <\/span>\r\n<span role=\"presentation\">\u00a0 {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"%s\\n\"<\/span>, <span class=\"cm-variable\">buf<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-comment\">\/\/\u5c06buf\u6240\u6307\u5411\u7684\u7f13\u5b58\u533a\u7684n\u4e2a\u5b57\u8282\u7684\u6570\u636e\u5199\u5165\u5230\u7531\u6587\u4ef6\u63cf\u8ff0\u7b26fd2\u6240\u6307\u793a\u7684\u6587\u4ef6\u4e2d<\/span><\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">write<\/span>(<span class=\"cm-variable\">fd2<\/span>, <span class=\"cm-variable\">buf<\/span>, <span class=\"cm-variable\">n<\/span>)<span class=\"cm-operator\">&lt;<\/span><span class=\"cm-variable\">n<\/span>) \u00a0 \u00a0<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"Write Error!!\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-keyword\">return<\/span> <span class=\"cm-number\">0<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">return<\/span> <span class=\"cm-number\">0<\/span>;<\/span>\r\n<span role=\"presentation\">}<\/span>\r\n<span role=\"presentation\"><span cm-text=\"\">\u200b<\/span><\/span><\/pre>\n<p cid=\"n35\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u6d4b\u8bd5\u8f93\u51fa\u4ee3\u7801\u5982\u4e0b\uff08GCC\u7f16\u8bd1\uff0c\u975eClang\uff09<\/span><\/p>\n<blockquote cid=\"n36\" mdtype=\"blockquote\">\n<p cid=\"n37\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ .\/redup <\/span><\/p>\n<p cid=\"n38\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">xxxxxxxxman<\/span><\/p>\n<p cid=\"n39\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">xxxxxxxxman<\/span><\/p>\n<p cid=\"n41\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">^C<\/span><\/p>\n<p cid=\"n42\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ cat text.txt <\/span><\/p>\n<p cid=\"n43\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">xxxxxxxxman<\/span><\/p>\n<p cid=\"n44\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ <\/span><\/p>\n<\/blockquote>\n<p cid=\"n45\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u53ef\u4ee5\u770b\u5230fd\u5c06\u63cf\u8ff0\u6307\u5411\u4e86text.txt\uff0c\u800cfd2\u7ecf\u8fc7dup\u64cd\u4f5c\uff0c\u76f8\u5f53\u4e8e\u505a\u4e86\u4e00\u6b21\u5f31\u62f7\u8d1d\uff0c\u4ee5\u540e\u6211\u4eec\u5bf9fd2\u8fdb\u884c\u7684\u64cd\u4f5c\u5c31\u76f8\u5f53\u4e8e\u5bf9fd\u8fdb\u884c\u7684\u64cd\u4f5c\u4e00\u6837\uff0c\u6b64\u65f6fd\u8fd9\u4e2a\u6807\u8bc6\u7b26\u4e5f\u4f9d\u65e7\u5b58\u5728\u3002<\/span><\/p>\n<h3 cid=\"n46\" mdtype=\"heading\" class=\"md-end-block md-heading\"><span md-inline=\"plain\" class=\"md-plain\">dup2<\/span><\/h3>\n<p cid=\"n47\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">dup2\u7684\u5b9a\u4e49\u662f\u5728dup1\u7684\u57fa\u7840\u4e0a\u53d1\u751f\u7684\u6539\u53d8<\/span><\/p>\n<pre spellcheck=\"false\" class=\"md-fences md-end-block ty-contain-cm modeLoaded\" lang=\"c\" cid=\"n48\" mdtype=\"fences\"><span role=\"presentation\"><span class=\"cm-variable-3\">int<\/span> <span class=\"cm-def\">dup2<\/span>(<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">oldfd<\/span>, <span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">newfd<\/span>);<\/span><\/pre>\n<p cid=\"n49\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">dup2\u4e0edup\u533a\u522b\u662fdup2\u53ef\u4ee5\u7528\u53c2\u6570newfd\u6307\u5b9a\u65b0\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u6570\u503c\u3002\u82e5\u53c2\u6570newfd\u5df2\u7ecf\u88ab\u7a0b\u5e8f\u4f7f\u7528\uff0c\u5219\u7cfb\u7edf\u5c31\u4f1a\u5c06newfd\u6240\u6307\u7684\u6587\u4ef6\u5173\u95ed\uff0c\u82e5newfd\u7b49\u4e8eoldfd\uff0c\u5219\u8fd4\u56denewfd,\u800c\u4e0d\u5173\u95ednewfd\u6240\u6307\u7684\u6587\u4ef6\u3002dup2\u6240\u590d\u5236\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e0e\u539f\u6765\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u5171\u4eab\u5404\u79cd\u6587\u4ef6\u72b6\u6001\u3002\u5171\u4eab\u6240\u6709\u7684\u9501\u5b9a\uff0c\u8bfb\u5199\u4f4d\u7f6e\u548c\u5404\u9879\u6743\u9650\u6216flags\u7b49\u3002<\/span><\/p>\n<p cid=\"n50\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u82e5dup2\u8c03\u7528\u6210\u529f\u5219\u8fd4\u56de\u65b0\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u8c03\u7528\u5931\u8d25\u5219\u8fd4\u56de-1. <\/span><\/p>\n<p cid=\"n51\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u4e00\u4e2a\u6d4b\u8bd5\u4ee3\u7801\u5982\u4e0b\uff1a<\/span><\/p>\n<pre spellcheck=\"false\" class=\"md-fences md-end-block ty-contain-cm modeLoaded\" lang=\"c\" cid=\"n52\" mdtype=\"fences\"><span role=\"presentation\"><span class=\"cm-meta\">#include &lt;unistd.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include &lt;fcntl.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include &lt;stdlib.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include &lt;string.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-meta\">#include &lt;stdio.h&gt;<\/span><\/span>\r\n<span role=\"presentation\"><span cm-text=\"\">\u200b<\/span><\/span>\r\n<span role=\"presentation\"><span class=\"cm-variable-3\">int<\/span> <span class=\"cm-def\">main<\/span>()<\/span>\r\n<span role=\"presentation\">{<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">oldfd<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">fd<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">int<\/span> <span class=\"cm-variable\">t<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable-3\">char<\/span> <span class=\"cm-variable-3\">*<\/span><span class=\"cm-variable\">buf<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-string\">\"This is a test!!!!\\n\"<\/span>;<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>((<span class=\"cm-variable\">oldfd<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">open<\/span>(<span class=\"cm-string\">\"orther.txt\"<\/span>,<span class=\"cm-variable\">O_RDWR<\/span><span class=\"cm-operator\">|<\/span><span class=\"cm-variable\">O_CREAT<\/span>,<span class=\"cm-number\">0644<\/span>))<span class=\"cm-operator\">==-<\/span><span class=\"cm-number\">1<\/span>) {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"open error\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">exit<\/span>(<span class=\"cm-operator\">-<\/span><span class=\"cm-number\">1<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable\">fd<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">dup2<\/span>(<span class=\"cm-variable\">oldfd<\/span>,<span class=\"cm-variable\">fileno<\/span>(<span class=\"cm-variable\">stdout<\/span>));<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">fd<\/span><span class=\"cm-operator\">==-<\/span><span class=\"cm-number\">1<\/span>) {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"dup2 error\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">exit<\/span>(<span class=\"cm-operator\">-<\/span><span class=\"cm-number\">1<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"dup2\u7684\u8fd4\u56de\u503c\uff1a%d\\n\"<\/span>,<span class=\"cm-variable\">fd<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable\">t<\/span><span class=\"cm-operator\">=<\/span><span class=\"cm-variable\">strlen<\/span>(<span class=\"cm-variable\">buf<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-comment\">\/\/\u672c\u5e94\u8be5\u5199\u5165\u5230stdout\u7684\u4fe1\u606f\uff0c\u4f46\u662f\u6807\u51c6\u8f93\u51fa\u5df2\u7ecf\u91cd\u5b9a\u5411\u5230\u76ee\u6807\u6587\u4ef6\u4e2d\uff0c\u6545\u5411\u6807\u51c6\u8f93\u51fa\u5199\u7684\u6570\u636e\u5c06\u4f1a\u5199\u5230\u76ee\u6807\u6587\u4ef6\u4e2d\u3002<\/span><\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">if<\/span>(<span class=\"cm-variable\">write<\/span>(<span class=\"cm-variable\">fileno<\/span>(<span class=\"cm-variable\">stdout<\/span>),<span class=\"cm-variable\">buf<\/span>,<span class=\"cm-variable\">t<\/span>)<span class=\"cm-operator\">!=<\/span><span class=\"cm-variable\">t<\/span>) {<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">printf<\/span>(<span class=\"cm-string\">\"write error!\\n\"<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0 \u00a0 \u00a0<span class=\"cm-variable\">exit<\/span>(<span class=\"cm-operator\">-<\/span><span class=\"cm-number\">1<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 }<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-variable\">close<\/span>(<span class=\"cm-variable\">fd<\/span>);<\/span>\r\n<span role=\"presentation\">\u00a0 \u00a0<span class=\"cm-keyword\">return<\/span> <span class=\"cm-number\">0<\/span>;<\/span>\r\n<span role=\"presentation\">}<\/span><\/pre>\n<p cid=\"n53\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">\u53ef\u4ee5\u7ed3\u5408\u4e0b\u9762\u7684\u7f16\u8bd1\u5185\u5bb9\uff0c\u53ef\u4ee5\u770b\u5f97\u51fadup2\u4e3b\u8981\u7528\u6765\u91cd\u5b9a\u5411\uff0c\u5c06oldFild\u76f4\u63a5\u53d6\u6d88\uff0c\u800c\u5c06\u539f\u6709\u7684\u5b57\u8282\u6d41\u5168\u90e8\u4f20\u9012\u7ed9newFile\u3002<\/span><\/p>\n<blockquote cid=\"n54\" mdtype=\"blockquote\">\n<p cid=\"n55\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ .\/redup2 <\/span><\/p>\n<p cid=\"n56\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ ls<\/span><\/p>\n<p cid=\"n57\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">orther.txt<\/span><span md-inline=\"tab\" class=\"md-tab\"> <\/span><span md-inline=\"plain\" class=\"md-plain\">redup.c<\/span><span md-inline=\"tab\" class=\"md-tab\"> <\/span><span md-inline=\"plain\" class=\"md-plain\">redup2<\/span><span md-inline=\"tab\" class=\"md-tab\"> <\/span><span md-inline=\"plain\" class=\"md-plain\">redup2.c<\/span><span md-inline=\"tab\" class=\"md-tab\"> <\/span><span md-inline=\"plain\" class=\"md-plain\">text.txt<\/span><\/p>\n<p cid=\"n58\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ cat orther.txt <\/span><\/p>\n<p cid=\"n59\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">This is a test!!!!<\/span><\/p>\n<p cid=\"n60\" mdtype=\"paragraph\" class=\"md-end-block md-p\"><span md-inline=\"plain\" class=\"md-plain\">(base) mt-007deMac-mini:Test mt-007$ <\/span><\/p>\n<\/blockquote>\n<div cid=\"n64\" mdtype=\"hr\" class=\"md-hr md-end-block\" tabindex=\"-1\">\n<hr \/>\n<\/div>\n<h3 cid=\"n66\" mdtype=\"heading\" class=\"md-end-block md-heading\"><span md-inline=\"plain\" class=\"md-plain\">\u7279\u6b8a\u5907\u6ce8<\/span><\/h3>\n<p cid=\"n67\" mdtype=\"paragraph\" class=\"md-end-block md-p md-focus\"><span md-inline=\"plain\" class=\"md-plain\">\u6709\u7684\u65f6\u5019\u8fd0\u884cC\u8bed\u8a00\u7684FILE\u64cd\u4f5c\u65e0\u6cd5\u8bfb\u53d6\u6587\u4ef6\uff0c\u4f46\u662f\u4f7f\u7528OC\u7684\u64cd\u4f5c\u8c03\u7528C\u7684\u4ee3\u7801\u5c31\u53ef\u4ee5\u8bfb\u53d6\uff0c\u8fd9\u5927\u6982\u7387\u662f\u56e0\u4e3a\u6743\u9650\u95ee\u9898\uff0c\u4e00\u822c\u800c\u8a00\u6587\u4ef6\u8def\u5f84\u5730\u5740\u8be5\u7528OC\u7684NSString\u5904\u7406\u5c31\u7528\u8fd9\u4e2a\u5904\u7406\u3002<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>OC \u65e5\u5fd7 \u5728\u672c\u9879\u76ee\u4e2d\uff0c\u60f3\u8981\u5b9e\u73b0\u4e00\u7c7b\u529f\u80fd\uff0c\u5373\u542f\u52a8\u540e\uff0c\u4e00\u5207\u8f93\u5165\u8f93\u51fa\u6d41\u5305\u62ec\u9519\u8bef\u6d41\u5168\u90e8\u81ea\u52a8\u7684\u5199\u5165\u5230\u4e00\u4e2a\u6587\u4ef6 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[45,88],"tags":[33,89],"class_list":["post-1006","post","type-post","status-publish","format-standard","hentry","category-c","category-objective-c","tag-c","tag-objective-c"],"views":1159,"_links":{"self":[{"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/posts\/1006","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/comments?post=1006"}],"version-history":[{"count":1,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/posts\/1006\/revisions"}],"predecessor-version":[{"id":1007,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/posts\/1006\/revisions\/1007"}],"wp:attachment":[{"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/media?parent=1006"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/categories?post=1006"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mustenaka.cn\/index.php\/wp-json\/wp\/v2\/tags?post=1006"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}