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网站规划与开发技术专业,安装了两个wordpress,深圳市建设,北京电力建设公司待遇从标准输入拷贝一个文本文件到标准输出#xff0c;使用dup2函数重定向到把一个磁盘文本文件拷贝到另一个磁盘文件的结尾处。#include sys/types.h #include sys/stat.h #include fcntl.h #include unistd.h #include stdio.h #includ…从标准输入拷贝一个文本文件到标准输出使用dup2函数重定向到把一个磁盘文本文件拷贝到另一个磁盘文件的结尾处。#include sys/types.h #include sys/stat.h #include fcntl.h #include unistd.h #include stdio.h #include errno.h #include stdlib.h #define MAXBUF 20 #define DEF_MODE S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH #define DEF_UMASK S_IWGRP|S_IWOTH ssize_t rio_readn(int fd, void *usrbuf, size_t n); ssize_t rio_writen(int fd, void *usrbuf, size_t n); int main(int argc, char **argv) { int n,fd1,fd2; char buf[MAXBUF]; fd1open(hello.txt,O_RDONLY,0); umask(DEF_UMASK); fd2 open(bar.txt, O_WRONLY|O_APPEND|O_CREAT, DEF_MODE); dup2(fd1,0); dup2(fd2,1); while((nrio_readn(STDIN_FILENO,buf,MAXBUF))! 0) rio_writen(STDOUT_FILENO,buf,n); exit(0); } ssize_t rio_readn(int fd, void *usrbuf, size_t n) { size_t nleft n; ssize_t nread; char *bufp usrbuf; while (nleft 0) { if ((nread read(fd, bufp, nleft)) 0) { if (errno EINTR) /* Interrupted by sig handler return */ nread 0; /* and call read() again */ else return -1; /* errno set by read() */ } else if (nread 0) break; /* EOF */ nleft - nread; bufp nread; } return (n - nleft); /* Return 0 */ } ssize_t rio_writen(int fd, void *usrbuf, size_t n) { size_t nleft n; ssize_t nwritten; char *bufp usrbuf; while (nleft 0){ if ((nwritten write(fd, bufp, nleft)) 0){ if (errno EINTR) /* Interrupted by sig handler return */ nwritten 0; /* and call write() again */ else return -1; /* errno set by write() */ } nleft - nwritten; bufp nwritten; } return n; }