{"id":1793,"date":"2019-01-04T09:25:29","date_gmt":"2019-01-04T01:25:29","guid":{"rendered":"https:\/\/www.yusian.com\/blog\/?p=1793"},"modified":"2020-12-02T09:45:36","modified_gmt":"2020-12-02T01:45:36","slug":"linux%e6%96%87%e4%bb%b6%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%93%8d%e4%bd%9c%e7%9b%b8%e5%85%b3%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/www.yusian.com\/blog\/cpp\/2019\/01\/04\/0925291793.html","title":{"rendered":"Linux\u6587\u4ef6\u7684\u57fa\u672c\u64cd\u4f5c\u76f8\u5173\u51fd\u6570"},"content":{"rendered":"<h3>1\u3001Linux\u865a\u62df\u5730\u5740\u7a7a\u95f4<\/h3>\n<ul>\n<li>Linux\u53ef\u6267\u884c\u6587\u4ef6\u683c\u5f0f\u4e3aELF\uff0c\u901a\u8fc7file xxxx\u53ef\u4ee5\u67e5\u770b\u6587\u4ef6\u7c7b\u578b<\/li>\n<li>\u865a\u62df\u5730\u5740\u7a7a\u95f4\u572832\u4f4d\u7cfb\u7edf\u4e2d\u4e3a4G\uff0c\u6bcf\u4e2a\u5e94\u7528\u7a0b\u5e8f\u90fd\u6709\u72ec\u7acb\u76844G<\/li>\n<li>\u5730\u5740\u4f4d\u4ece\u9ad8\u5230\u4f4e\u5206\u522b\u4e3a\uff1a\n<ul>\n<li>3G ~ 4G\uff1aLinux Kernel\uff0c\u5185\u5b58\u7ba1\u7406\u3001\u8fdb\u7a0b\u7ba1\u7406\u3001\u8bbe\u5907\u9a71\u52a8\u3001VFS\u865a\u62df\u6587\u4ef6\u7cfb\u7edf<\/li>\n<li>0G ~ 3G<\/li>\n<li>\u73af\u5883\u53d8\u91cf<\/li>\n<li>\u547d\u4ee4\u884c\u53c2\u6570<\/li>\n<li>\u6808\u7a7a\u95f4<\/li>\n<li>\u5171\u4eab\u5e93<\/li>\n<li>\u5806\u7a7a\u95f4<\/li>\n<li>ELF<\/li>\n<li>\u672a\u521d\u59cb\u5316\u7684\u5168\u5c40\u53d8\u91cf\n<ul>\n<li>\u5df2\u521d\u59cb\u5316\u7684\u5168\u5c40\u53d8\u91cf<\/li>\n<li>\u4ee3\u7801\u6bb5\u3001\u4e8c\u8fdb\u5236\u673a\u5668\u6307\u4ee4<\/li>\n<li>\u53d7\u4fdd\u62a4\u7684\u5730\u5740\uff080 ~ 4K\uff09<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>2\u3001Linux\u6587\u4ef6\u57fa\u672c\u7ec4\u6210<!--more--><\/h3>\n<ul>\n<li>denty\uff08\u76ee\u5f55\u9879\uff09\uff0c\u4e00\u4e2a\u76ee\u5f55\u9879\u76f8\u5f53\u4e8e\u4e00\u4e2a\u786c\u8fde\u63a5\n<ul>\n<li>\u6587\u4ef6\u540d<\/li>\n<li>inode\u7f16\u53f7<\/li>\n<\/ul>\n<\/li>\n<li>iNode\n<ul>\n<li>struct stat<\/li>\n<li>\u5927\u5c0f\u3001\u6743\u9650\u3001\u7c7b\u578b\u3001\u6240\u6709\u8005\u3001\u7ec4\u3001<\/li>\n<li>\u5b58\u50a8\u6307\u9488\u5730\u5740\u2014->\u6570\u636e\u5757\u2014\u2014>\u78c1\u76d8<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h4>1\u3001open\u51fd\u6570<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;sys\/types.h&gt;\n#include &lt;sys\/stat.h&gt;\n#include &lt;fcntl.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;unistd.h&gt;\n#include &lt;stdlib.h&gt;\nconst char* file_path = \"file.txt\";\nint main(){\n    \/\/ 1\u3001\u6253\u5f00\u6587\u4ef6\uff0c\u4ee5\u8bfb\u5199\u7684\u65b9\u5f0f\n    int fd = open(file_path, O_RDWR);\n    \/\/ 1.1\u3001\u5982\u679c\u6253\u5f00\u5931\u8d25\uff0c\u5219\u521b\u5efa\u6587\u4ef6\uff0c\u6743\u9650644\n    if (fd == -1){\n    \/\/ \u521b\u5efa\u51fa\u6765\u7684\u6587\u4ef6\u5b9e\u9645\u6743\u9650\u662f\u5f53\u524d\u6307\u5b9a\u6743\u9650\u4e0e\u672c\u5730\u63a9\u7801\u53d6\u53cd\u540e\u7684\u4e0e\u8fd0\u7b97\n    \/\/ umask\u53ef\u4ee5\u67e5\u770b\u6216\u4fee\u6539\u672c\u5730\u63a9\u7801\uff0c\u4e00\u822c\u662f0002\n    fd = open(file_path, O_RDWR | O_CREAT, 0644);\n    }\n    \/\/ 1.2\u3001\u5982\u679c\u521b\u5efa\u5931\u8d25\uff0c\u5219\u9000\u51fa\u7a0b\u5e8f\n    if (fd == -1){\n    perror(\"Create file\");\n           exit(0);\n    }else{\n    \/\/ 2\u3001\u6253\u5f00\u6587\u4ef6\u540e\u7684\u64cd\u4f5c\n        printf(\"OK!\\n\");\n    }\n    \/\/ 3\u3001\u64cd\u4f5c\u7ed3\u675f\u540e\u5173\u95ed\u6587\u4ef6\n    int ret = close(fd);\n    \/\/ 3.1\u3001\u5173\u95ed\u5931\u8d25\u540e\u7ed9\u51fa\u9519\u8bef\u63d0\u793a\n    if (ret == -1){\n        perror(\"Close file\");\n    }else{\n        printf(\"Closed file success!!\\n\");\n    }\n    return 0;\n}\n<\/code><\/pre>\n<h4>2\u3001read&amp;write\u57fa\u672c\u64cd\u4f5c<\/h4>\n<pre><code class=\"language-c line-numbers\">\/\/ close\u9700\u8981\u5f15\u5165\u7684\u5934\u6587\u4ef6\n#include &lt;unistd.h&gt;\n\n\/\/ open\u51fd\u6570\u9700\u8981\u5bfc\u5165\u7684\u4e09\u4e2a\u5934\u6587\u4ef6\n#include &lt;fcntl.h&gt;\n#include &lt;sys\/types.h&gt;\n#include &lt;sys\/stat.h&gt;\n\n\/\/ \u6807\u51c6\u7684C\u8bed\u8a00\u5934\u6587\u4ef6\n#include &lt;stdlib.h&gt;\n#include &lt;stdio.h&gt;\n\nconst char* file_r = \"file.txt\";\nconst char* file_w = \"write.txt\";\nint main(){\n    \/\/ \u6253\u5f00\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u6587\u4ef6\n    int fd_r = open(file_r, O_RDONLY);\n    if (fd_r == -1){\n        perror(\"Open file\");\n        exit(1);\n    }\n    \/\/ \u521b\u5efa\u4e00\u4e2a\u65b0\u6587\u4ef6\uff0c\u51c6\u5907\u5199\u5165\n    int fd_w = open(file_w, O_CREAT | O_WRONLY, 0664);\n    if (fd_w == -1){\n        \/\/ \u5982\u679copen\u5931\u8d25\uff0c\u51fd\u6570\u4f1a\u4fee\u6539errno\u5168\u5c40\u53d8\u91cf\u503c\uff0c\u800cperror\u4f1a\u8bfb\u53d6\u8be5\u5168\u5c40\u53d8\u91cf\u7684\u503c\n        perror(\"Create file\");\n        exit(1);\n    }\n    \/\/ \u8bfb\u53d6\u4e0e\u5199\u5165,\u6bcf\u6b21\u8bfb\u53d610\u4e2a\u5b57\u8282\uff0csizeof(buf)\u662f10\n    \/\/ \u5982\u679c\u662fchar* buf[10]\u7684\u8bdd\uff0csizeof(buf)\u662f80\n    char buf[100] = {0};\n    int count = read(fd_r, buf, sizeof(buf));\n    if (count == -1){\n        perror(\"Read file\");\n        exit(1);\n    }\n    while(count){\n        int ret = write(fd_w, buf, count);\n        printf(\"Write bytes %d\\n\", ret);\n        count = read(fd_r, buf, sizeof(buf));\n    }\n    close(fd_r);\n    close(fd_w);\n\n    return 0;\n}\n<\/code><\/pre>\n<h4>3\u3001lseek\u51fd\u6570\u7684\u4f7f\u7528<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;sys\/stat.h&gt;\n#include &lt;sys\/types.h&gt;\n#include &lt;fcntl.h&gt;\n\n#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\nint main(){\n    const char* file = \"lseek.txt\";\n    int fd = open(file, O_RDWR);\n    if (fd == -1){\n        perror(\"Open file\");\n        exit(1);\n    }\n    \/\/ off_t lseek(int fd, off_t offset, int whence);\n    \/\/ whence\u7684\u503c\u6709SEEK_SET\u3001SEEK_CUR\u3001SEEK_END\n    \/\/ \u4ece\u5c3e\u90e8\u79fb\u52a80\u4e2a\u4f4d\u7f6e\uff0c\u8fd4\u56de\u7684\u504f\u79fb\u91cf\u5373\u4e3a\u6587\u4ef6\u5f53\u524d\u603b\u957f\u5ea6\n    int ret = lseek(fd, 0, SEEK_END);\n    printf(\"file length = %d\\n\", ret);\n\n    \/\/ \u6587\u4ef6\u62d3\u5c55\uff0c\u4ece\u5c3e\u90e8\u79fb\u52a82000\u4e2a\u4f4d\u7f6e\n    ret = lseek(fd, 2000, SEEK_END);\n    printf(\"return value : %d\\n\", ret);\n\n    \/\/ \u5728\u5f53\u524d\u4f4d\u7f6e\u5199\u5165\u5185\u5bb9\uff0c\u6587\u4ef6\u88ab\u62d3\u5c55\uff0c\u5982\u679c\u4e0d\u5199\u5165\uff0c\u4e0d\u4f1a\u6539\u53d8\u5f53\u524d\u6587\u4ef6\u5927\u5c0f\n    \/\/ \u5199\u5165\u5185\u5bb9\u540e\uff0c\u4e2d\u95f4\u7684\u504f\u79fb\u4f1a\u88ab\u586b\u5145\n    write(fd, \"\", 1);\n    close(fd);\n    return 0;\n}\n<\/code><\/pre>\n<h4>4\u3001stat\u51fd\u6570\u7684\u4f7f\u7528<\/h4>\n<ul>\n<li>stat\u662fLinux\u4e0b\u7684\u547d\u4ee4\uff0c\u540e\u9762\u53ef\u4ee5\u76f4\u63a5\u8ddf\u6587\u4ef6\u540d\uff0c\u5982\uff1astat a.out\n<pre><code class=\"language-cmd line-numbers\">parallels@ubuntu:~\/Linux\/fopen$ stat a.out\nFile: a.out\nSize: 8560          Blocks: 24         IO Block: 4096   regular file\nDevice: 801h\/2049d    Inode: 2498221     Links: 1\nAccess: (0775\/-rwxrwxr-x)  Uid: ( 1000\/parallels)   Gid: ( 1000\/parallels)\nAccess: 2019-01-04 16:08:45.366586892 +0800\nModify: 2019-01-04 16:08:44.438516020 +0800\nChange: 2019-01-04 16:08:44.438516020 +0800\nBirth: -\n<\/code><\/pre>\n<\/li>\n<li>stat\u662f\u4e00\u4e2a\u7ed3\u6784\u4f53\n<pre><code class=\"language-c line-numbers\">struct stat {\n  dev_t     st_dev;         \/* ID of device containing file *\/\n  ino_t     st_ino;         \/* Inode number *\/\n  mode_t    st_mode;        \/* File type and mode *\/\n  nlink_t   st_nlink;       \/* Number of hard links *\/\n  uid_t     st_uid;         \/* User ID of owner *\/\n  gid_t     st_gid;         \/* Group ID of owner *\/\n  dev_t     st_rdev;        \/* Device ID (if special file) *\/\n  off_t     st_size;        \/* Total size, in bytes *\/\n  blksize_t st_blksize;     \/* Block size for filesystem I\/O *\/\n  blkcnt_t  st_blocks;      \/* Number of 512B blocks allocated *\/\n\n  \/* Since Linux 2.6, the kernel supports nanosecond\n  precision for the following timestamp fields.\n  For the details before Linux 2.6, see NOTES. *\/\n\n  struct timespec st_atim;  \/* Time of last access *\/\n  struct timespec st_mtim;  \/* Time of last modification *\/\n  struct timespec st_ctim;  \/* Time of last status change *\/\n\n  #define st_atime st_atim.tv_sec      \/* Backward compatibility *\/\n  #define st_mtime st_mtim.tv_sec\n  #define st_ctime st_ctim.tv_sec\n};\n<\/code><\/pre>\n<\/li>\n<li>stat\u662f\u4e00\u4e2a\u51fd\u6570<\/p>\n<\/li>\n<li>\n<p>lstat\u4e0estat\u53c2\u6570\u76f8\u540c\uff0c\u4e0d\u540c\u7684\u662flstat\u4e0d\u7a7f\u900f\uff0c\u5bf9\u5f53\u524d\u6587\u4ef6\u64cd\u4f5c<\/p>\n<p>&#8220;`c<br \/>\n#include &lt;sys\/types.h&gt;<\/p>\n<p>&lt;h1&gt;include &lt;sys\/stat.h&gt;&lt;\/h1&gt;<\/p>\n<p>#include &lt;unistd.h&gt;&lt;\/p&gt;&lt;\/li&gt;<br \/>\n&lt;\/ul&gt;<\/p>\n<p>&lt;p&gt;int stat(const char *pathname, struct stat *statbuf);<br \/>\n   int fstat(int fd, struct stat *statbuf);<br \/>\n\/\/ lstat\u4e0estat\u7684\u533a\u522b\u5728\u4e8e\uff0clstat\u4e0d\u8ffd\u8e2a\u8f6f\u94fe\u63a5\uff0c\u76f4\u63a5\u4f5c\u7528\u4e8e\u5f53\u524d\u6587\u4ef6<br \/>\n   int lstat(const char *pathname, struct stat *statbuf);<\/p>\n<p>&lt;pre&gt;&lt;code class=&quot;line-numbers&quot;&gt;* stat\u51fd\u6570\u7684\u7b80\u5355\u5e94\u7528<\/p>\n<p>   &#8220;`c<br \/>\n   #include &lt;stdlib.h&gt;<br \/>\n   #include &lt;stdio.h&gt;<\/p>\n<p>   #include &lt;sys\/types.h&gt;<br \/>\n   #include &lt;sys\/stat.h&gt;<br \/>\n   #include &lt;unistd.h&gt;<\/p>\n<p>   int main(int argc, char* argv[]){<br \/>\n       if (argc &lt; 2){<br \/>\n           printf(&#8220;.\/a.out filename\\n&#8221;);<br \/>\n       exit(1);<br \/>\n       }<br \/>\n       struct stat statbuf;<br \/>\n       int ret = stat(argv[1], &amp;statbuf);<br \/>\n       if (ret == -1){<br \/>\n           perror(&#8220;stat&#8221;);<br \/>\n       exit(1);<br \/>\n       }<br \/>\n       mode_t mode = statbuf.st_mode;<br \/>\n       printf(&#8220;mode: %d\\n&#8221;, mode);<br \/>\n       printf(&#8220;\u6587\u4ef6\u7c7b\u578b\uff1a%o\\n&#8221;, mode &amp; 0170000);<br \/>\n       printf(&#8220;\u6587\u4ef6\u6240\u6709\u8005\u6743\u9650\uff1a%o\\n&#8221;, mode &amp; 0700);<br \/>\n       printf(&#8220;\u8bbe\u5907ID\uff1a%lo\\n&#8221;, statbuf.st_dev);<br \/>\n       printf(&#8220;INode\uff1a%ld\\n&#8221;, statbuf.st_ino);<br \/>\n       printf(&#8220;Links\uff1a%ld\\n&#8221;, statbuf.st_nlink);<br \/>\n       printf(&#8220;Uid\uff1a%d\\n&#8221;, statbuf.st_uid);<br \/>\n       printf(&#8220;Gid\uff1a%d\\n&#8221;, statbuf.st_gid);<br \/>\n       printf(&#8220;Size\uff1a%ld\\n&#8221;, statbuf.st_size);<br \/>\n       return 0;<br \/>\n   }<br \/>\n   &#8220;`<\/p>\n<p>#### 5\u3001access\u51fd\u6570<\/p>\n<p>* \u5224\u65ad\u6587\u4ef6\u662f\u5426\u62e5\u6709\u67d0\u4e2a\u6743\u9650<\/p>\n<p>* man 2 access\u67e5\u770b\u51fd\u6570\u8bf4\u660e<\/p>\n<p>  &#8220;`c<br \/>\n  #include &lt;unistd.h&gt;<\/p>\n<p>  #include &lt;stdio.h&gt;<br \/>\n  #include &lt;stdlib.h&gt;<\/p>\n<p>  int main(int argc, char* argv[]){<br \/>\n      if (argc &lt; 2){<br \/>\n          printf(&#8220;.\/a.out filename\\n&#8221;);<br \/>\n      exit(1);<br \/>\n      }<br \/>\n      int ret = access(argv[1], W_OK);<br \/>\n      if (ret == -1){<br \/>\n          perror(&#8220;Access&#8221;);<br \/>\n      exit(1);<br \/>\n      }<br \/>\n      printf(&#8220;you can write this file \\n&#8221;);<br \/>\n      return 0;<\/p>\n<p>  }<br \/>\n  &#8220;`<\/p>\n<p>#### 6\u3001chmod\u51fd\u6570<\/p>\n<p>&#8220;`c<br \/>\n#include &lt;sys\/stat.h&gt;<br \/>\n#include &lt;stdio.h&gt;<br \/>\n#include &lt;stdlib.h&gt;<\/p>\n<p>int main(int argc, char* argv[]){<br \/>\n    if (argc &lt; 2){<br \/>\n        printf(&#8220;.\/a.out filename\\n&#8221;);<br \/>\n        exit(1);<br \/>\n    }<br \/>\n    int ret = chmod(argv[1], 0664);<br \/>\n    if (ret == -1){<br \/>\n        perror(&#8220;chmod&#8221;);<br \/>\n        exit(1);<br \/>\n    }<br \/>\n    printf(&#8220;Success!!\\n&#8221;);<br \/>\n    return 0;<br \/>\n}<br \/>\n<\/code><\/p>\n<ul>\n<li>\u6743\u9650\u4e5f\u53ef\u4ee5\u901a\u8fc7\u53c2\u6570\u4f20\u8fdb\u6765\uff0c\u4f7f\u7528strtol( )\u51fd\u6570\u5c06\u5b57\u7b26\u4e32\u8f6c\u6210\u6743\u9650\u53c2\u6570\u76848\u8fdb\u5236\u503c\n<pre><code class=\"language-c line-numbers\">#include &lt;sys\/stat.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n  if (argc &lt; 3){\n      printf(\"e.g: .\/a.out filename 777\\n\");\n      exit(1);\n  }\n  long mode = strtol(argv[2], NULL, 8);\n  int ret = chmod(argv[1], mode);\n  if (ret == -1){\n      perror(\"chmod\");\n      exit(1);\n  }\n  printf(\"Success!!\\n\");\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h4>7\u3001chown\u51fd\u6570<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n    if (argc &lt; 4){\n        printf(\"e.g: .\/a.out filepath user group\\n\");\n        exit(1);\n    }\n    int ret = chown(argv[1], atoi(argv[2]), atoi(argv[3]));\n    if (ret == -1){\n        perror(\"chown\");\n        exit(1);\n    }\n    printf(\"Success!!\\n\");\n    return 0;\n}\n<\/code><\/pre>\n<h4>8\u3001truncate\u51fd\u6570\u4f7f\u7528<\/h4>\n<ul>\n<li>\uff08truncate\u82f1\u6587\u7ffb\u8bd1\u662f\u201c\u622a\u65ad\u201d\u7684\u610f\u601d\uff0c\u8d85\u51fa\u90e8\u5206\u7a7a\u6d1e\u586b\u5145\uff09<\/p>\n<\/li>\n<li>\n<p>Linux\u672c\u8eab\u6709truncate\u547d\u4ee4<\/p>\n<ul>\n<li><code>truncate xxx \u2014size 1000<\/code><\/li>\n<\/ul>\n<pre><code class=\"language-c line-numbers\">#include &lt;sys\/types.h&gt;\n#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n  if (argc &lt; 3){\n      printf(\".\/a.out filename n\\n\");\n      exit(1);\n  }\n  int ret = truncate(argv[1], atoi(argv[2]));\n  if (ret == -1){\n      perror(\"truncate\");\n      exit(1);\n  }\n  printf(\"Success!!\\n\");\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h4>9\u3001link\u51fd\u6570\u4f7f\u7528<\/h4>\n<ul>\n<li>Linux\u672c\u8eab\u6709link\u547d\u4ee4\n<ul>\n<li>link filename linkname \/\/ \u786c\u94fe\u63a5<\/li>\n<li>ln filename linkname \/\/ \u786c\u94fe\u63a5<\/li>\n<li>ln -s filename linkname \/\/ \u8f6f\u94fe\u63a5\uff0c\u5feb\u6377\u65b9\u5f0f<\/li>\n<\/ul>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n  if (argc &lt; 3){\n      printf(\"e.g: .\/a.out filename linkname\\n\");\n      exit(1);\n  }\n  int ret = link(argv[1], argv[2]);\n  if (ret == -1){\n      perror(\"link\");\n      exit(1);\n  }\n  printf(\"Success!!\\n\");\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h4>10\u3001symlink\u51fd\u6570\u7684\u4f7f\u7528<\/h4>\n<ul>\n<li>\u8f6f\u94fe\u63a5\uff0c\u5373ln -s<\/li>\n<\/ul>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n    if (argc &lt; 3){\n        printf(\".\/a.out filename symlink\\n\");\n        exit(1);\n    }\n    int ret = symlink(argv[1], argv[2]);\n    if (ret == -1){\n        perror(\"symlink\");\n        exit(1);\n    }\n    printf(\"Success!!!\\n\");\n    return 0;\n}\n<\/code><\/pre>\n<h4>11\u3001readlink\u51fd\u6570<\/h4>\n<ul>\n<li>\u5bf9\u5e94\u7684Linux\u547d\u4ee4\u4e3areadlink\n<ul>\n<li>readlink linkname<\/li>\n<\/ul>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n  if (argc &lt; 2){\n      printf(\"e.g: .\/a.out linkpath\\n\");\n      exit(1);\n  }\n  char buf[512];\n  int ret = readlink(argv[1], buf, sizeof(buf));\n  if (ret == -1){\n      perror(\"radlink\");\n      exit(1);\n  }\n  \/\/ \u8fd4\u56deret\u5373\u4e3alink\u8def\u5f84\u7684\u957f\u5ea6\uff0c\u5728\u6700\u540e\u9762\u52a0\u7ed3\u675f\u5b57\u7b26\n  buf[ret] = '\\0';\n  printf(\"%s\\n\", buf);\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h4>12\u3001unlink\u51fd\u6570<\/h4>\n<ul>\n<li>\u5bf9\u5e94\u7684Linlux\u547d\u4ee4\u4e3aunlink\n<ul>\n<li>unlink  filename<\/li>\n<\/ul>\n<\/li>\n<li>unlink\u547d\u4ee4\u4f1a\u5220\u9664\u5f53\u524d\u6587\u4ef6\u53ca\u94fe\u63a5\u6570\uff0c\u4f46\u5982\u679c\u5f53\u524d\u6587\u4ef6\u5904\u4e8e\u6253\u5f00\u72b6\u6001\uff0c\u5219\u8be5\u6587\u4ef6\u7684\u5b9e\u9645\u5220\u9664\u4f1a\u5728\u5173\u95ed\u540e\u6267\u884c\uff0c\u56e0\u6b64\u53ef\u4ee5\u5728\u7a0b\u5e8f\u4e2d\u505a\u4e3a\u4e34\u65f6\u6587\u4ef6\u64cd\u4f5c\uff0copen\u540e\u6267\u884c\u4e00\u6b21unlink\u64cd\u4f5c\uff0cclose\u540e\u6e05\u9664<\/li>\n<\/ul>\n<pre><code class=\"language-c line-numbers\">#include &lt;sys\/types.h&gt;\n#include &lt;sys\/stat.h&gt;\n#include &lt;fcntl.h&gt;\n#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;string.h&gt;\n\nint main(){\n    \/\/ \u6253\u5f00\u4e34\u65f6\u6587\u4ef6(\u5b9e\u73b0\u4e0a\u4f1a\u5728\u78c1\u76d8\u4e2d\u521b\u5efa\u4e00\u4e2a\u65b0\u6587\u4ef6)\n    int fd = open(\"tempfile\", O_CREAT | O_RDWR, 0664);\n    if (fd == -1){\n        perror(\"open\");\n        exit(1);\n    }\n    \/\/ \u5220\u9664\u4e34\u65f6\u6587\u4ef6\uff0c\u5728\u6587\u4ef6\u88ab\u5173\u95ed\u540e\u5f7b\u5e95\u5220\u9664\uff0c\u4e0d\u5f71\u54cd\u5f53\u524d\u6587\u4ef6\u64cd\u4f5c\n    unlink(\"tempfile\");\n\n    \/\/ \u5199\u5165\u6587\u4ef6\u6570\u636e\n    const char* txt = \"Hello Linux!!!\\n\";\n    int len = strlen(txt);\n    write(fd, txt, len);\n\n    \/\/ \u91cd\u7f6e\u6587\u4ef6\u64cd\u4f5c\u6307\u9488\n    lseek(fd, 0, SEEK_SET);\n\n    \/\/ \u8bfb\u53d6\u6587\u4ef6\u5185\u5bb9\n    char buf[512] = {0};\n    len = read(fd, buf, len);\n\n    \/\/ \u5c06\u8bfb\u53d6\u51fa\u6765\u7684\u5185\u5bb9\u5199\u5230\u5c4f\u5e55\u4e0a\n    \/\/ \u6587\u4ef6\u63cf\u8ff0\u7b26\u8868\u4e2d\u7684\u6587\u4ef6\u63cf\u8ff0\u7b260\uff1astdin\u8f93\u5165\u6d41\u30011\uff1astdout\u8f93\u51fa\u6d41\u30012\uff1astderr\n    write(1, buf, len);\n\n    \/\/ \u5173\u95ed\u6587\u4ef6\uff0c\u5173\u95ed\u540e\u6587\u4ef6\u5c06\u88ab\u5f7b\u5e95\u5220\u9664\n    close(fd);\n    return 0;\n}\n<\/code><\/pre>\n<h4>12\u3001rename\u51fd\u6570<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n    if (argc &lt; 3){\n        printf(\"e.g: .\/a.out filenam e newname\\n\");\n        exit(1);\n    }\n    int ret = rename(argv[1], argv[2]);\n    if (ret == -1){\n        perror(\"rename\");\n        exit(1);\n    }\n    printf(\"%s is renamed to %s\\n\", argv[1], argv[2]);\n    return 0;\n}\n<\/code><\/pre>\n<h4>13\u3001chdir\u3001getcwd\u51fd\u6570<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n\nint main(int argc, char* argv[]){\n    if (argc &lt; 2){\n        printf(\"e.g: .\/a.out path\\n\");\n        exit(1);\n    }\n    int ret = chdir(argv[1]);\n    if (ret == -1){\n        perror(\"chdir\");\n        exit(1);\n    }\n    char buf[512] = {0};\n    char* path = getcwd(buf, sizeof(buf));\n    printf(\"Current path:%s\\n\", path);\n    return 0;\n}\n<\/code><\/pre>\n<h4>14\u3001mkdir\u3001rmdir\u3001opendir\u3001readdir\u3001closedir<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;dirent.h&gt;\n#include &lt;string.h&gt;\n\nvoid print_dir(const char* path){\n    \/\/ 1\u3001\u6253\u5f00\u76ee\u5f55\n    DIR* dir = opendir(path);\n    if (dir == NULL){\n        perror(\"opendir\");\n        exit(1);\n    }\n    \/\/ 2\u3001\u8bfb\u53d6\u76ee\u5f55\n    struct dirent* dirent = readdir(dir);\n    \/\/ \u5faa\u73af\u8bfb\u53d6\uff0c\u51fd\u6570\u4f1a\u81ea\u52a8\u5bfb\u627e\u4e0b\u4e00\u4e2a\uff0c\u5982\u679c\u6ca1\u6709\u5219\u8fd4\u56de\u7a7a\n    \/\/ \u914d\u5408\u5faa\u73af\u4e2d\u6700\u540e\u4e00\u53e5\u4f7f\u7528\uff0c\u5426\u5219\u662f\u6b7b\u5faa\u73af\n    while(dirent){\n        \/\/ \u83b7\u53d6\u5f53\u524d\u5143\u7d20\u7684\u540d\u79f0(\u53ef\u80fd\u662f\u76ee\u5f55\u3001\u6587\u4ef6\u3001\u94fe\u63a5\u3001\u7ba1\u9053\u7b49)\n        char* subpath = dirent-&gt;d_name;\n        \/\/ \u83b7\u53d6\u5f53\u524d\u5143\u7d20\u7c7b\u578b\n        int d_type = dirent-&gt;d_type;\n        \/\/ \u8fc7\u6ee4\u540d\u79f0\u4e3a.\u6216..\u7684\u76ee\u5f55\n        if (strcmp(subpath, \".\") &amp;&amp; strcmp(subpath, \"..\")){\n            \/\/ \u62fc\u63a5\u5b57\u7b26\u4e32\uff0c\u5c06\u5f53\u524d\u8def\u5f84\u4e0e\u5f53\u524d\u5143\u7d20\u62fc\u63a5\u6210\u5168\u8def\u5f84\n            char *p = malloc(strlen(path)+strlen(subpath)+1);\n            sprintf(p, \"%s\/%s\", path, subpath);\n            \/\/ \u8f93\u51fa\u5f53\u524d\u5143\u7d20\u7684\u5168\u8def\u5f84\n            printf(\"%s\\n\", p);\n            \/\/ \u5982\u679c\u662f\u76ee\u5f55\uff0c\u5219\u9012\u5f52\n            if (d_type == DT_DIR){\n                print_dir(p);\n            }\n            free(p);\n        }\n        dirent = readdir(dir);\n    }\n    \/\/ 3\u3001\u5173\u95ed\u76ee\u5f55\n    closedir(dir);\n}\nint main(int argc, char* argv[]){\n    if (argc &lt; 2){\n        printf(\"e.g: .\/a.out dirpath\\n\");\n        exit(1);\n    }\n    \/\/ \u4ece\u4f20\u8fdb\u6765\u7684\u76ee\u5f55\u5f00\u59cb\u9012\u5f52\u6253\u5370\n    print_dir(argv[1]);\n    return 0;\n}\n<\/code><\/pre>\n<h4>15\u3001dup\u3001dup2\u51fd\u6570\uff08\u6587\u4ef6\u63cf\u8ff0\u7b26\u62f7\u8d1d\uff09<\/h4>\n<ul>\n<li>dup\n<pre><code class=\"language-c line-numbers\">#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;unistd.h&gt;\n#include &lt;sys\/types.h&gt;\n#include &lt;sys\/stat.h&gt;\n#include &lt;fcntl.h&gt;\n\nint main(){\n\n  int fd = open(\"a.txt\", O_CREAT | O_RDWR, 0664);\n  if (fd == -1){\n      perror(\"open\");\n      exit(1);\n  }\n  printf(\"fd:%d\\n\", fd);\n  char txt[] = \"Hello Linux!!\\n\";\n  write(fd, txt, sizeof(txt));\n  int dup_fd = dup(fd);\n  printf(\"dup_fd:%d\\n\", dup_fd);\n  char dup_txt[] = \"I am a function named dup!!\\n\u201d;\n  \/\/ \u7ed3\u679c\u662fdup_txt\u6570\u636e\u4f1a\u5199\u5165\u5230a.txt\u4e2d\n  write(dup_fd, dup_txt, sizeof(dup_txt));\n  close(fd);\n  close(dup_fd);\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<li>dup2\n<pre><code class=\"language-c line-numbers\">#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;unistd.h&gt;\n#include &lt;fcntl.h&gt;\n\nint main(){\n  int df1 = open(\"a.txt\", O_RDWR);\n  printf(\"df1:%d\\n\", df1);\n  int df2 = open(\"dup2.txt\", O_CREAT | O_RDWR, 0664);\n  printf(\"df2:%d\\n\", df2);\n  \/\/ \u8fd9\u53e5\u8bdd\u7684\u610f\u601d\u662f\uff1a\u7528df1\u6765\u6307\u5411df2\uff0c\u90a3\u4e48\u539fdf1\u4f1a\u88ab\u5173\u95ed\n  int df_dup2 = dup2(df2, df1);\n  printf(\"df_dup2:%d\\n\", df_dup2);\n  char txt1[] = \"txt1\\n\";\n  char txt2[] = \"txt2\\n\";\n  char txt_dup2[] = \"txt_dup2\\n\u201d;\n  \/\/ \u6700\u7ec8\u7ed3\u679c\u662f\u6240\u6709\u7684\u6570\u636e\u90fd\u5199\u5728dup2.txt\u6587\u4ef6\u4e2d\uff0c\u539fa.txt\u6ca1\u6709\u5f71\u54cd\n  write(df1, txt1, sizeof(txt1));\n  write(df2, txt2, sizeof(txt2));\n  write(df_dup2, txt_dup2, sizeof(txt_dup2));\n  close(df1);\n  close(df2);\n  close(df_dup2);\n  return 0;\n}\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h4>16\u3001fcntl\u51fd\u6570\uff08\u4fee\u6539\u6587\u4ef6\u63cf\u8ff0\u7b26\u64cd\u4f5c\u6743\u9650\uff09<\/h4>\n<pre><code class=\"language-c line-numbers\">#include &lt;unistd.h&gt;\n#include &lt;fcntl.h&gt;\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;string.h&gt;\n\nint main(){\n    char *p = \"I am a student!!!\\n\";\n    char *q = \"Just do it and you can get it!\\n\";\n    \/\/ 1\u3001\u6253\u5f00\u6587\u4ef6\uff0c\u4ee5\u53ea\u5199\u7684\u65b9\u5f0f\u6253\u5f00\n    int fd = open(\"a.txt\", O_WRONLY);\n    if (fd == -1){\n        perror(\"open\");\n        exit(1);\n    }\n    \/\/ 2\u3001\u5199\u5165\u5185\u5bb9\uff0c\u6b64\u65f6\u4f1a\u4ece\u5934\u5f00\u59cb\u5199\uff0c\u8986\u76d6\u539f\u6709\u7684\u5185\u5bb9\n    int ret = write(fd, p, strlen(p));\n    if (ret == -1){\n        perror(\"write\");\n        exit(1);\n    }\n    \/\/ 3.1\u3001\u83b7\u53d6\u6587\u4ef6\u63cf\u8ff0\u7b26\u5f53\u524d\u7684\u64cd\u4f5c\u6743\u9650\n    int flag = fcntl(fd, F_GETFL, 0);\n    if (flag == -1){\n        perror(\"fcntl getflag\");\n        exit(1);\n    }\n    \/\/ 3.2\u3001\u4fee\u6539\u6587\u4ef6\u63cf\u8ff0\u7b26\u64cd\u4f5c\u6743\u9650\n    flag |= O_APPEND;\n    ret = fcntl(fd, F_SETFL, flag);\n    if (ret == -1){\n        perror(\"fcntl setflag\");\n        exit(1);\n    }\n    \/\/ 4\u3001\u518d\u6b21\u5199\u5165\uff0c\u4f1a\u5339\u914d\u65b0\u7684\u64cd\u4f5c\u6743\u9650\uff0c\u56e0\u4e3a\u6dfb\u52a0\u4e86\u201c\u8ffd\u52a0\u201d\u6743\u9650\uff0c\u65b0\u5199\u5165\u7684\u5185\u5bb9\u4f1a\u88ab\u8ffd\u56de\u5230\u5185\u5bb9\u7684\u6700\u540e\u9762\n    ret = write(fd, q, strlen(q));\n    if (ret == -1){\n        perror(\"write\");\n        exit(1);\n    }\n    return 0;\n}\n<\/code><\/pre>\n<p><strong>\u6267\u884c\u7ed3\u679c\uff1a<\/strong><\/p>\n<pre><code class=\"language-cmd line-numbers\">yusian@SianMac2:~\/Linux\/source$ cat a.txt\nHello Linux!!\nI am a function named dup!!\nyusian@SianMac2:~\/Linux\/source$ .\/a.out\nyusian@SianMac2:~\/Linux\/source$ cat a.txt\nI am a student!!!\nm a function named dup!!\nJust do it and you can get it!\nyusian@SianMac2:~\/Linux\/source$\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>1\u3001Linux\u865a\u62df\u5730\u5740\u7a7a\u95f4 Linux\u53ef\u6267\u884c\u6587\u4ef6\u683c\u5f0f\u4e3aELF\uff0c\u901a\u8fc7file xxxx\u53ef\u4ee5\u67e5\u770b\u6587\u4ef6\u7c7b\u578b \u865a\u62df\u5730\u5740\u7a7a\u95f4\u572832\u4f4d\u7cfb\u7edf\u4e2d\u4e3a4G\uff0c\u6bcf\u4e2a\u5e94\u7528\u7a0b\u5e8f\u90fd\u6709\u72ec\u7acb\u76844G \u5730\u5740\u4f4d\u4ece\u9ad8\u5230\u4f4e\u5206\u522b\u4e3a\uff1a 3G ~ 4G\uff1aLinux Kernel\uff0c\u5185\u5b58\u7ba1\u7406\u3001\u8fdb\u7a0b\u7ba1\u7406\u3001\u8bbe\u5907\u9a71\u52a8\u3001VFS\u865a\u62df\u6587\u4ef6\u7cfb\u7edf 0G ~ 3G \u73af\u5883\u53d8\u91cf \u547d\u4ee4\u884c\u53c2\u6570 \u6808\u7a7a\u95f4 \u5171\u4eab\u5e93 \u5806\u7a7a\u95f4 ELF \u672a\u521d\u59cb\u5316\u7684\u5168\u5c40\u53d8\u91cf \u5df2\u521d\u59cb\u5316\u7684\u5168\u5c40\u53d8\u91cf \u4ee3\u7801\u6bb5\u3001\u4e8c\u8fdb\u5236\u673a\u5668\u6307\u4ee4 \u53d7\u4fdd\u62a4\u7684\u5730\u5740\uff080 ~ 4K\uff09 2\u3001Linux\u6587\u4ef6\u57fa\u672c\u7ec4\u6210<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[88],"tags":[310,311],"class_list":["post-1793","post","type-post","status-publish","format-standard","hentry","category-cpp","tag-linux","tag-311"],"_links":{"self":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts\/1793","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/comments?post=1793"}],"version-history":[{"count":0,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts\/1793\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/media?parent=1793"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/categories?post=1793"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/tags?post=1793"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}