struct stat

Updated: May 06, 2022

Data structure for information about a file or directory

Synopsis:

The definition of struct stat is complicated; see <sys/stat.h> for details.

Description:

The stat structure is used to store information about a file or directory. In QNX Neutrino 7.0 or later, there are several forms of the stat structure:

struct __stat_t32_2001
Includes 32-bit time_t fields, but not the nanosecond-resolution timestamps. This is what earlier versions of the OS supported and is the default for 32-bit architectures.
struct __stat_t32_2008
Includes 32-bit time_t fields, and the nanosecond-resolution timestamps.
struct __stat_t64_2008
Includes 64-bit time_t fields, and the nanosecond-resolution timestamps. This is the default for 64-bit architectures.

The struct stat is defined to be one of the above, depending on which architecture you compile your code for. You can use stat_convert_form() to convert one form of the structure to another.

The members include:

ino_t st_ino
The file serial number for the object.
off_t st_size
The meaning of this field depends on the object's type:
For a: This field is:
Regular file The size of the object, in bytes
Symbolic link The length, in bytes, of the pathname contained in the symbolic link
Shared memory object The length, in bytes
Typed memory object The length, in bytes
dev_t st_dev
The ID of the device that contains the file. A device ID consists of:
  • a major number in the range 0 through 63
  • a minor number in the range 0 through 1023

These macros manipulate device IDs:

major( device )
Extract the major number from a device ID.
minor( device )
Extract the minor number from a device ID.
makedev( node, major, minor)
Build a device ID from the given numbers. Currently, the node argument isn't used and must be zero.
dev_t st_rdev
The device ID, if the object is a character- or block-special file. This includes major and minor numbers, just like st_dev.

For special named files (S_IFNAM), the subtype is encoded in st_rdev:

  • _S_INSEM — semaphore subtype
  • _S_INSHD — shared data subtype
  • _S_INMQ — message queue subtype
  • _S_INTMO — typed memory object
  • _S_QNX_SPECIAL — QNX special type
uid_t st_uid
The user ID of the object.
gid_t st_gid
The group ID of the object.
time_t st_mtime, time_t st_atime, time_t st_ctime
(POSIX 2001) The time that the data was last modified, accessed, or the file status was changed, respectively, expressed as the number of seconds since January 1, 1970.
struct timespec st_mtim, struct timespec st_atim, struct timespec st_ctim
(POSIX 2008 only) The time that the data was last modified, accessed, or the file status was changed, respectively, expressed as the number of seconds and nanoseconds since January 1, 1970. For backwards compatibility, st_mtime, st_atime, and st_ctime correspond to the tv_sec field of st_mtim, st_atim, and st_ctim.
mode_t st_mode
Flags that identify the following:
  • file type
  • presence of an extended Access Control List (QNX Neutrino 6.6 or later)
  • set-on-execution behavior
  • access permissions

Three-digit octal modes include the access permissions; some utilities, such as find, use six-digit octal modes that include the rest:

Name Octal value Meaning
S_IFBLK 060000 Block special file
S_IFCHR 020000 Character special file
S_IFDIR 040000 Directory
S_IFIFO 010000 FIFO special file
S_IFLNK 120000 Symbolic link
S_IFNAM 050000 Special named file
S_IFREG 100000 Regular file
S_IFSOCK 140000 Socket
_S_ACL_EXT 200000 (QNX Neutrino 6.6 or later) The file has an extended ACL. For more information, see Access Control Lists (ACLs) in the Working with Files chapter of the QNX Neutrino User's Guide, and the Working with ACLs chapter of the QNX Neutrino Programmer's Guide.
S_ISUID 004000 Set user ID on execution. The process's effective user ID is set to the file's owner when the file is run as a program. On a regular file, this bit should be cleared on any write.
S_ISGID 002000 Set group ID on execution. The process's effective group ID is set to the file's group when the file is run as a program. On a regular file, this bit should be cleared on any write.
S_ISVTX 001000 Sticky bit
S_IRUSR 000400 Owner has read permission
S_IWUSR 000200 Owner has write permission
S_IXUSR 000100 Owner has execute/search permission
S_IRWXU 000700 Owner has read, write, and execute/search permissions; a bitwise inclusive OR of S_IRUSR, S_IWUSR and S_IXUSR
S_IRGRP 000040 Group has read permission
S_IWGRP 000020 Group has write permission
S_IXGRP 000010 Group has execute/search permission
S_IRWXG 000070 Group has read, write, and execute/search permissions; a bitwise inclusive OR of S_IRGRP, S_IWGRP and S_IXGRP
S_IROTH 000004 Others have read permission
S_IWOTH 000002 Others have write permission
S_IXOTH 000001 Others have execute/search permission
S_IRWXO 000007 Others have read, write, and execute/search permissions; a bitwise inclusive OR of S_IROTH, S_IWOTH and S_IXOTH

S_IFMT is a mask that isolates the file-type bits. For information about macros that you can use to check the file type, see Macros,” below.

The following bits define miscellaneous permissions used by other implementations:

Bit Equivalent
S_IEXEC S_IXUSR
S_IREAD S_IRUSR
S_IWRITE S_IWUSR
nlink_t st_nlink
The number of hard links to the object.
blksize_t st_blocksize
The block size, in bytes.
int32_t st_nblocks
The number of blocks (of size st_blocksize) that the object is using.
blksize_t st_blksize
The preferred I/O block size for the object.
blkcnt_t st_blocks
The number of 512-bytes blocks that the object is using.

Macros

The following macros test whether a file is of a specified type. The value m supplied to the macros is the value of the st_mode field of a stat structure. The macros evaluate to a nonzero value if the test is true, and zero if the test is false.

S_ISBLK(m)
Test for block special file.
S_ISCHR(m)
Test for character special file.
S_ISDIR(m)
Test for directory file.
S_ISFIFO(m)
Test for FIFO.
S_ISLNK(m)
Test for symbolic link.
S_ISNAM(m)
Test for special named file.
S_ISREG(m)
Test for regular file.
S_ISSOCK(m)
Test for socket.

These macros test whether a file is of the specified type. The value of the buf argument supplied to the macros is a pointer to a stat structure. The macro evaluates to a nonzero value if the specified object is implemented as a distinct file type and the specified file type is contained in the stat structure referenced by the pointer buf. Otherwise, the macro evaluates to zero.

S_TYPEISMQ(buf)
Test for message queue.
S_TYPEISSEM(buf)
Test for semaphore.
S_TYPEISSHM(buf)
Test for shared memory object.

Classification:

POSIX 1003.1 with QNX Neutrino extensions