Detailed explanation of stat function

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Linux File system management of system functions （ Two ）

stat function

​ effect ： Get file information

​ The header file ：include <sys/types.h> #include <sys/stat.h> #include <unistd.h>

​ The function prototype ：int stat(const char *path, struct stat *buf)

​ Return value ： Successfully returns 0, Failure to return -1;

​ Parameters ： File path （ name ）,struct stat Type of structure

struct stat Structure details ：

struct stat
{
    dev_t     st_dev;     /* ID of device containing file */ The equipment number used in the document 
    ino_t     st_ino;     /* inode number */     Inode number  
    mode_t    st_mode;    /* protection */   The pattern corresponding to the file , file , Directory etc. 
    nlink_t   st_nlink;   /* number of hard links */     Number of hard connections to the file   
    uid_t     st_uid;     /* user ID of owner */     Owner user id 
    gid_t     st_gid;     /* group ID of owner */    Group identification number   
    dev_t     st_rdev;    /* device ID (if special file) */  The equipment number of the equipment file 
    off_t     st_size;    /* total size, in bytes */  File capacity in bytes    
    blksize_t st_blksize; /* blocksize for file system I/O */  The size of the disk block containing the file    
    blkcnt_t  st_blocks;  /* number of 512B blocks allocated */  The disk block occupied by this file   
    time_t    st_atime;   /* time of last access */  The last time the file was accessed    
    time_t    st_mtime;   /* time of last modification */ / The last time the file was modified    
    time_t    st_ctime;   /* time of last status change */  The last time the state of the file was changed    
};

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stat In structure st_mode The following situations are defined ：

    S_IFMT   0170000     Bit mask of file type 
    S_IFSOCK 0140000     Socket 
    S_IFLNK 0120000      Symbolic connection 
    S_IFREG 0100000      General documents 
    S_IFBLK 0060000      Block device 
    S_IFDIR 0040000      Catalog 
    S_IFCHR 0020000      Character device 
    S_IFIFO 0010000      fifo 
​
    S_ISUID 04000      Of documents (set user-id on execution) position 
    S_ISGID 02000      Of documents (set group-id on execution) position 
    S_ISVTX 01000      Of documents sticky position 
​
    S_IRUSR(S_IREAD) 00400      The file owner has read permission 
    S_IWUSR(S_IWRITE)00200      The owner of the file has write permission 
    S_IXUSR(S_IEXEC) 00100      The file owner has executable rights 
​
    S_IRGRP 00040              The user group has read permission 
    S_IWGRP 00020              The user group has write permission 
    S_IXGRP 00010              The user group has executable rights 
​
    S_IROTH 00004              Other users have read permission 
    S_IWOTH 00002              Other users have write access 
    S_IXOTH 00001              Other users have executable rights 
​
     The above file types are in POSIX Macro definitions for checking these types are defined in ：
    S_ISLNK (st_mode)     Judge whether it is a symbolic connection 
    S_ISREG (st_mode)     Is it a general document 
    S_ISDIR (st_mode)     Is it a directory 
    S_ISCHR (st_mode)     Whether it is a character device file 
    S_ISBLK (s3e)         First in first out 
    S_ISSOCK (st_mode)    Is it socket
     If a directory has sticky position (S_ISVTX), It means that the files in this directory can only be used by the owner of the file 、 The owner of this directory or root To delete or rename , stay linux in , The most typical is this /tmp It's a catalog .
​

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st_mode Structure

st_mode Mainly consists of 3 Some information ：

• 15-12 Bit save file type
• 11-9 Bit saves the information set when executing the file
• 8-0 Bit save file access

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