讀取 Linux file info (stat)

讀取 Linux 的檔案資訊

Linux 的檔案有很多資訊，即使只用到檔案大小也是很方便。

stat

• struct stat

  stat 的資料結構

      #include <sys/stat.h>
  
      struct stat {
          dev_t     st_dev;         /* ID of device containing file */
          ino_t     st_ino;         /* Inode number */
          mode_t    st_mode;        /* File type and mode */
          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;     /* Block size for filesystem I/O */
          blkcnt_t  st_blocks;      /* Number of 512B blocks allocated */
  
          /* Since Linux 2.6, the kernel supports nanosecond
              precision for the following timestamp fields.
              For the details before Linux 2.6, see NOTES. */
  
          struct timespec st_atim;  /* Time of last access */
          struct timespec st_mtim;  /* Time of last modification */
          struct timespec st_ctim;  /* Time of last status change */
  
          #define st_atime st_atim.tv_sec      /* Backward compatibility */
          #define st_mtime st_mtim.tv_sec
          #define st_ctime st_ctim.tv_sec
      };
  

• struct stat

  讀取檔案 (這裡讀 .gitignore)

      #include <stdio.h>    // for printf
      #include <time.h>     // for ctime
      #include <sys/stat.h>
  
      int main()
      {
          struct stat st;
          // 0 success, -1 failed
          // error code: errno
          if(stat(".gitignore", &st) == -1){
              return -1;
          }
          printf("I-node number:             %ld\n", (long) st.st_ino);
          printf("Mode:                      %lo (octal)\n", (unsigned long) st.st_mode);
          printf("Link count:                %ld\n", (long) st.st_nlink);
          printf("Ownership:                 UID=%ld   GID=%ld\n", (long) st.st_uid, (long) st.st_gid);
          printf("device containing file id: %ld\n", (long) st.st_dev);
          printf("device id:                 %ld\n", (long) st.st_rdev);
          printf("File size:                 %lld bytes\n", (long long) st.st_size);
          printf("Preferred I/O block size:  %ld bytes\n", (long) st.st_blksize);
          printf("Blocks allocated:          %lld\n", (long long) st.st_blocks);
          printf("Last status change:        %s", ctime(&st.st_ctime));
          printf("Last file access:          %s", ctime(&st.st_atime));
          printf("Last file modification:    %s", ctime(&st.st_mtime));
          return 0;
      }
  

      I-node number:             20057552
      Mode:                      100664 (octal)
      Link count:                1
      Ownership:                 UID=1000   GID=1000
      device containing file id: 66306
      device id:                 0
      File size:                 16 bytes
      Preferred I/O block size:  4096 bytes
      Blocks allocated:          8
      Last status change:        Tue Mar 29 14:03:01 2022
      Last file access:          Sun Oct  9 19:02:52 2022
      Last file modification:    Thu Jun 17 10:20:57 2021
  

參考資料 :

1.Linux manual page

2.程式人生