#include <sys/stat.h> int fstat(int fildes, struct stat *buf);
If fildes references a shared memory object, the implementation shall update in the stat structure pointed to by the buf argument the st_uid, st_gid, st_size, and st_mode fields, and only the S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH file permission bits need be valid. The implementation may update other fields and flags.
If fildes references a typed memory object, the implementation shall update in the stat structure pointed to by the buf argument the st_uid, st_gid, st_size, and st_mode fields, and only the S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH file permission bits need be valid. The implementation may update other fields and flags.
The buf argument is a pointer to a stat structure, as defined in <sys/stat.h>, into which information is placed concerning the file.
For all other file types defined in this volume of POSIX.1-2017, the structure members st_mode, st_ino, st_dev, st_uid, st_gid, st_atim, st_ctim, and st_mtim shall have meaningful values and the value of the st_nlink member shall be set to the number of links to the file.
An implementation that provides additional or alternative file access control mechanisms may, under implementation-defined conditions, cause fstat() to fail.
The fstat() function shall update any time-related fields (as described in the Base Definitions volume of POSIX.1-2017, Section 4.9, File Times Update), before writing into the stat structure.
The fstat() function may fail if:
The following sections are informative.
The following example shows how to obtain file status information for a file named /home/cnd/mod1. The structure variable buffer is defined for the stat structure. The /home/cnd/mod1 file is opened with read/write privileges and is passed to the open file descriptor fildes.
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
struct stat buffer;
int status;
...
fildes = open("/home/cnd/mod1", O_RDWR);
status = fstat(fildes, &buffer);
The Base Definitions volume of POSIX.1-2017, Section 4.9, File Times Update, <sys_stat.h>, <sys_types.h>
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