Linux 下stat和access函数

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1.stat既有命令也有同名函数，用来获取文件Inode里主要信息（即文件类型、文件权限、创建/修改/访问时间等就是ls -l看到的相关的信息），stat 跟踪符号链接，lstat不跟踪符号链接。可以通过man 2 stat查看相关的信息。

 #include <sys/types.h> #include <sys/stat.h> #include <unistd.h>int stat(const char *path, struct stat *buf);int fstat(int fd, struct stat *buf);int lstat(const char *path, struct stat *buf);struct stat {               dev_t     st_dev;     /* ID of device containing file */               ino_t     st_ino;     /* inode number */               mode_t    st_mode;    /* protection */               nlink_t   st_nlink;   /* number of hard links */               uid_t     st_uid;     /* user ID of owner */               gid_t     st_gid;     /* group ID of owner */               dev_t     st_rdev;    /* device ID (if special file) */               off_t     st_size;    /* total size, in bytes */               blksize_t st_blksize; /* blocksize for filesystem I/O */               blkcnt_t  st_blocks;  /* number of 512B blocks allocated */               time_t    st_atime;   /* time of last access */               time_t    st_mtime;   /* time of last modification */ //指的是修改文件内容               time_t    st_ctime;   /* time of last status change */ //指的是修改inode属性            };

#include <sys/types.h>#include <sys/stat.h>#include<time.h>#include <unistd.h>#include<errno.h>#include<stdio.h>int main(int argc, char *argv[]){struct stat filestat;if (argc < 2){printf("Usage: %s <pathname>\n", argv[0]);return 0;}if (stat(argv[1], &filestat) == -1){perror("stat error:");return 0;}printf("File type:                ");switch (filestat.st_mode & S_IFMT)// 0170000   bit mask for the file type bit fields{case S_IFBLK:printf("block device\n");break;case S_IFCHR:printf("character device\n");break;case S_IFDIR:printf("directory\n");break;case S_IFIFO:printf("FIFO/pipe\n");break;case S_IFLNK:printf("symlink\n");break;case S_IFREG:printf("regular file\n");break;case S_IFSOCK:printf("socket\n");break;default:printf("unknown?\n");break;}printf("I-node number:            %ld\n", (long) filestat.st_ino);printf("Mode:                     %lo (octal)\n",(unsigned long) filestat.st_mode);printf("Link count:               %ld\n", (long) filestat.st_nlink);printf("Ownership:                UID=%ld   GID=%ld\n", (long) filestat.st_uid,(long) filestat.st_gid);printf("Preferred I/O block size: %ld bytes\n", (long) filestat.st_blksize);printf("File size:                %lld bytes\n", (long long) filestat.st_size);printf("Blocks allocated:         %lld\n", (long long) filestat.st_blocks);printf("Last status change:       %s", ctime(&filestat.st_ctime));printf("Last file access:         %s", ctime(&filestat.st_atime));printf("Last file modification:   %s", ctime(&filestat.st_mtime));return 0;}

2.access函数

功能: 确定文件或文件夹的访问权限。即，检查某个文件的存取方式，比如说是只读方式、只写方式等。如果指定的存取方式有效，则函数返回0，否则函数返回-1。

#include <unistd.h>int access(const char *pathname, int mode);

按实际用户ID和实际组ID测试,跟踪符号链接
参数mode
R_OK 是否有读权限
W_OK 是否有写权限
X_OK 是否有执行权限
F_OK 测试一个文件是否存在

#include<stdio.h>#include<unistd.h>int main(int argc, char *argv[]){if (argc < 2){printf("Usage: %s <pathname>\n", argv[0]);return 0;}if(access(argv[1],R_OK|X_OK|W_OK)==0){printf("read wirte execute \n");}return 0;}

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