sys/stat.h - data returned by the stat() function
The <sys/stat.h> header defines the structure of the data returned by the functions fstat(), lstat(), and stat().
The structure stat contains at least the following members:
dev_t st_dev ID of device containing file ino_t st_ino file serial number mode_t st_mode mode of file (see below) nlink_t st_nlink number of links to the file uid_t st_uid user ID of file gid_t st_gid group ID of file dev_t st_rdev device ID (if file is character or block special) off_t st_size file size in bytes (if file is a regular file) time_t st_atime time of last access time_t st_mtime time of last data modification time_t st_ctime time of last status change blksize_t st_blksize a filesystem-specific preferred I/O block size for this object. In some filesystem types, this may vary from file to file blkcnt_t st_blocks number of blocks allocated for this object
File serial number and device ID taken together uniquely identify the file within the system. The blkcnt_t, blksize_t, dev_t, ino_t, mode_t, nlink_t, uid_t, gid_t, off_t and time_t types are defined as described in <sys/types.h>. Times are given in seconds since the Epoch.
The following symbolic names for the values of st_mode are also defined:
- type of file
- block special
- character special
- FIFO special
- symbolic link
File mode bits:
- read, write, execute/search by owner
- read permission, owner
- write permission, owner
- execute/search permission, owner
- read, write, execute/search by group
- read permission, group
- write permission, group
- execute/search permission, group
- read, write, execute/search by others
- read permission, others
- write permission, others
- execute/search permission, others
- set-user-ID on execution
- set-group-ID on execution
- on directories, restricted deletion flag
The bits defined by S_IRUSR, S_IWUSR, S_IXUSR, S_IRGRP, S_IWGRP, S_IXGRP, S_IROTH, S_IWOTH, S_IXOTH, S_ISUID, S_ISGID and S_ISVTX are unique.
S_IRWXU is the bitwise OR of S_IRUSR, S_IWUSR and S_IXUSR.
S_IRWXG is the bitwise OR of S_IRGRP, S_IWGRP and S_IXGRP.
S_IRWXO is the bitwise OR of S_IROTH, S_IWOTH and S_IXOTH.
Implementations may OR other implementation-dependent bits into S_IRWXU, S_IRWXG and S_IRWXO, but they will not overlap any of the other bits defined in this document. The file permission bits are defined to be those corresponding to the bitwise inclusive OR of S_IRWXU, S_IRWXG and S_IRWXO.
The following macros will test whether a file is of the specified type. The value m supplied to the macros is the value of st_mode from a stat structure. The macro evaluates to a non-zero value if the test is true, 0 if the test is false.
- Test for a block special file.
- Test for a character special file.
- Test for a directory.
- Test for a pipe or FIFO special file.
- Test for a regular file.
- Test for a symbolic link.
The implementation may implement message queues, semaphores, or shared memory objects as distinct file types. The following 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 non-zero 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 buf. Otherwise, the macro evaluates to zero.
- Test for a message queue
- Test for a semaphore
- Test for a shared memory object
The following are declared as functions and may also be defined as macros. Function prototypes must be provided for use with an ISO C compiler.
int chmod(const char *, mode_t); int fchmod(int, mode_t); int fstat(int, struct stat *); int lstat(const char *, struct stat *); int mkdir(const char *, mode_t); int mkfifo(const char *, mode_t); int mknod(const char *, mode_t, dev_t); int stat(const char *, struct stat *); mode_t umask(mode_t);
Use of the macros is recommended for determining the type of a file.
chmod(), fchmod(), fstat(), lstat(), mkdir(), mkfifo(), mknod(), stat(), umask(), <sys/types.h>.