I/O重定向程序

从标准输入拷贝文件或从指定磁盘文件拷贝到标准输出。

#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #define DEF_MODE S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH #define DEF_UMASK S_IWGRP|S_IWOTH #define RIO_BUFSIZE 8192 #define MAXLINE 10 typedef struct { int rio_fd; /* Descriptor for this internal buf */ int rio_cnt; /* unread bytes in internal buf */ char *rio_bufptr; /* Next unread bytes in internal buf */ char rio_buf[RIO_BUFSIZE]; /* Internal buffer */ } rio_t; void rio_readinitb(rio_t *rp, int fd); ssize_t rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen); static ssize_t rio_read(rio_t *rp, char *usrbuf, size_t n); ssize_t rio_writen(int fd, void *usrbuf, size_t n); int main(int argc, char **argv) { int n,fd1; rio_t rio; char buf[MAXLINE]; if((argc!=1) && (argc!=2)) { fprintf(stderr,"usage : %s <infile>\n",argv[0]); exit(1); } if(argc==2){ int fd; if((fd=open(argv[1], O_RDONLY,0))<0) { fprintf(stderr,"Couldn'tread%s\n",argv[1]); exit(1); } dup2(fd, STDIN_FILENO); close(fd); } rio_readinitb(&rio, STDIN_FILENO); while((n = rio_readlineb(&rio, buf, MAXLINE)) != 0) rio_writen(STDOUT_FILENO, buf, n); 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; } void rio_readinitb(rio_t *rp, int fd) { rp->rio_fd = fd; rp->rio_cnt = 0; rp->rio_bufptr = rp->rio_buf; } ssize_t rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen) { int n, rc; char c, *bufp = usrbuf; for (n = 1; n < maxlen; n++) { if ((rc = rio_read(rp, &c, 1)) == 1) { *bufp++ = c; if (c == '\n') break; } else if (rc == 0) { if (n == 1) return 0; /* EOF, no data read */ else break; /* EOF, some data was read */ } else return -1; /* Error */ } *bufp = 0; return n; } static ssize_t rio_read(rio_t *rp, char *usrbuf, size_t n) { int cnt; while (rp->rio_cnt <= 0) { /* Refill if buf is empty */ rp->rio_cnt = read(rp->rio_fd, rp->rio_buf, sizeof(rp->rio_buf)); if (rp->rio_cnt < 0) { if (errno != EINTR) /* Interrupted by sig handler return */ return -1; } else if (rp->rio_cnt == 0) /* EOF */ return 0; else rp->rio_bufptr = rp->rio_buf; /* Reset buffer ptr */ } /* Copy min(n, rp->rio_cnt) bytes from internal buf to user buf */ cnt = n; if (rp->rio_cnt < n) cnt = rp->rio_cnt; memcpy(usrbuf, rp->rio_bufptr, cnt); rp->rio_bufptr += cnt; rp->rio_cnt -= cnt; return cnt; }