mmap的使用

#include <sys/mman.h> /* for mmap and munmap */#include <sys/types.h> /* for open */#include <sys/stat.h> /* for open */#include <fcntl.h> /* for open */#include <unistd.h> /* for lseek and write */#include <stdio.h>#include <string.h> /* for memcpy */int main(int argc, char **argv){ int fd; char *mapped_mem, * p; int flength = 1024; void * start_addr = 0; fd = open(argv[1], O_RDWR | O_CREAT, S_IRUSR | S_IWUSR); flength = lseek(fd, 1, SEEK_END); write(fd, "/0", 1); /* 在文件最后添加一个空字符，以便下面printf正常工作 */ lseek(fd, 0, SEEK_SET); start_addr = 0; mapped_mem = mmap(start_addr, flength, PROT_READ | PROT_WRITE, //允许写入 MAP_PRIVATE, //允许其它进程访问此内存区域 fd, 0); if( mapped_mem == MAP_FAILED) { printf("MAP_FAILED /n"); return -1; } printf("%c", mapped_mem[flength]); /* 使用映射区域. */ //printf("%s/n", mapped_mem); /* 为了保证这里工作正常，参数传递的文件名最好是一个文本文 */ close(fd); msync(mapped_mem, flength-2, MS_SYNC); munmap(mapped_mem, flength); return 0;}