学步园

#define  _FILE_OFFSET_BITS 64
#define  __USE_XOPEN2K
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <getopt.h>

const struct option dcache_options[] = {
    {"sync",0,NULL,'s'},
    {"help",0,NULL,'h'},
    {NULL,0,NULL,0}
};

void usage(char* proc_name,int exit_code)
{
    printf("dcache is an utility to drop file cache.\n"
        "usage:%s [-s] file\n"
        "\t-s,--sync, sync data before drop cache.\n"
        "\t-h,--help, print help.\n",proc_name);
    exit(exit_code);
}

int dcache(int fd, int sync_data)
{
    off_t off,len;
    struct stat buf;
    int save_errno;
    save_errno = errno;

    if (sync_data) {
        if (fsync(fd) < 0) {
            printf("%s\n",strerror(errno));
            errno = save_errno;
            return -1;
        }
    } 

    if (fstat(fd,&buf) < 0) {
        printf("%s\n",strerror(errno)); 
        errno = save_errno;
        return -1;
    }  

    off = 0;
    len = buf.st_size;
    if (posix_fadvise(fd,off,len,POSIX_FADV_DONTNEED) < 0) {
        printf("%s\n",strerror(errno)); 
        errno = save_errno;
        return -1;
    }

    return 0;
}

int main(int argc, char* argv[])
{
    int c,fd;
    char* file; 
    int long_index = 0;
    int print_help = 0; 
    int sync_data = 0;
    while ((c = getopt_long(argc,argv,"sh",dcache_options,&long_index)) != -1) {
        switch (c) {
        case 's':
            sync_data = 1;
            break;
        case 'h':
            print_help = 1;
            break;
        default:
            printf("unknown option -%c\n",c);  
            usage(argv[0],EXIT_FAILURE);
            break;
        }
    }
    if (print_help) {
        usage(argv[0],EXIT_SUCCESS);
    }
    if (optind >= argc) {
        printf("file name required\n");     
        exit(EXIT_FAILURE);
    } 
    for (c = optind; c < argc; ++c) {
        file = argv[c];
        if ((fd = open(file,O_RDWR)) < 0) {
            printf("open %s failed.\n",file);   
        } else {
            printf("drop cache of %s %s.\n",file,dcache(fd,sync_data) == 0?"success":"failed");
            close(fd);
        }
    }
    exit(EXIT_SUCCESS);
}