How to print time_t Linux __linux

Linux under time_t Time type
The time_t type is defined in the Time.h header file:

#ifndef __time_t  
#define __TIME_T  
typedef  long  time_t;  
#endif  

Visible, time_t is actually a long integer type. The value is expressed as the number of seconds from UTC (Coordinated Universal Time) January 1, 1970 00:00 00 seconds (also known as the Linux system epoch) to the current moment. Because of the time_t type length, it represents a time that cannot be later than January 19, 2038 03:14 07 seconds (UTC). In order to be able to represent a longer time, you can save the calendar time with 64-bit or longer cosmetic numbers, which are not detailed here.
Use the time () function to get the time_t value of the current period and use the CTime () function to convert the time_t to a local time string.
Note: UTC time is sometimes referred to as GMT time, in fact UTC and GMT are almost identical concepts. They all refer to Greenwich Mean time, but UTC is a more formal term. The difference is that the former is an astronomical concept, and the latter is based on an atomic clock.

The format for printing time under Linux is:

printf ("%lu\n", time);

Linux usually involves the printing of time parameters: for example, get the file attribute stat function, which is a prototype:

  int stat (const char *path, struct stat *buf);
  BUF is a file information structure body, the structure body members are as follows:
  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 the last access * *
   time_t    st_mtime;   /* Time of the last modification * *
   time_t    st_ctime;   /* Time of last status change *
           /};

The Shmctl function in the shared memory will also involve the time parameter, so it is unavoidable to print it in the Linux development.