設定檔案的檔案訪問許可權為：rw-r--r--
描述：rw- (user許可權) / r– (group許可權) / r– (others許可權)
r: 讀許可權 w: 寫許可權 x: 執行許可權
要求：輸入檔名，列印輸出該檔案初始許可權，以及修改為rw-r--r--後的許可權
知識點：設定檔案的多個許可權位，對這些許可權位進行按位或操作即可。S_IRUSR | S_IWUSR
程式碼:
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/stat.h>
int main(int argc,char *argv[])
{
struct stat buf;
int res;
if(argc!=2)
{
perror("引數不正確!正確格式:./main filename");
exit(1);
}
res=stat(argv[1],&buf);
if(res<0)
{
perror("stat error");
exit(1);
}
printf("初始檔案 %s 的許可權資訊:\n",argv[1]);
//if(buf.st_mode&S_IRWXU) printf("user read write execute\n");
if(buf.st_mode&S_IRUSR) printf("user read \n");
if(buf.st_mode&S_IWUSR) printf("user write \n");
if(buf.st_mode&S_IXUSR) printf("user execute\n");
//if(buf.st_mode&S_IRWXG) printf("group read write execute\n");
if(buf.st_mode&S_IRGRP) printf("group read \n");
if(buf.st_mode&S_IWGRP) printf("group write\n");
if(buf.st_mode&S_IXGRP) printf("group execute\n");
//if(buf.st_mode&S_IRWXO) printf("other read write execute\n");
if(buf.st_mode&S_IROTH) printf("other read \n");
if(buf.st_mode&S_IWOTH) printf("other write\n");
if(buf.st_mode&S_IXOTH) printf("other execute\n");
chmod(argv[1],S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
res=stat(argv[1],&buf);
if(res<0)
{
perror("stat error");
exit(1);
}
printf("更改後文件 %s 的許可權資訊:\n",argv[1]);
if(buf.st_mode&S_IRUSR) printf("user read \n");
if(buf.st_mode&S_IWUSR) printf("user write \n");
if(buf.st_mode&S_IXUSR) printf("user execute\n");
if(buf.st_mode&S_IRGRP) printf("group read \n");
if(buf.st_mode&S_IWGRP) printf("group write\n");
if(buf.st_mode&S_IXGRP) printf("group execute\n");
if(buf.st_mode&S_IROTH) printf("other read \n");
if(buf.st_mode&S_IWOTH) printf("other write\n");
if(buf.st_mode&S_IXOTH) printf("other execute\n");
}