fstat (2)
Leading comments
Copyright (c) 1980, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and t...
NAME
stat lstat fstat fstatat - get file statusLIBRARY
Lb libcSYNOPSIS
In sys/types.h In sys/stat.h Ft int Fn stat const char *path struct stat *sb Ft int Fn lstat const char *path struct stat *sb Ft int Fn fstat int fd struct stat *sb Ft int Fn fstatat int fd const char *path struct stat *buf int flagDESCRIPTION
The Fn stat system call obtains information about the file pointed to by Fa path . Read, write or execute permission of the named file is not required, but all directories listed in the path name leading to the file must be searchable.The Fn lstat system call is like Fn stat except in the case where the named file is a symbolic link, in which case Fn lstat returns information about the link, while Fn stat returns information about the file the link references.
The Fn fstat system call obtains the same information about an open file known by the file descriptor Fa fd .
The Fn fstatat system call is equivalent to Fn stat and Fn lstat except in the case where the Fa path specifies a relative path. In this case the status is retrieved from a file relative to the directory associated with the file descriptor Fa fd instead of the current working directory.
The values for the Fa flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in In fcntl.h :
- AT_SYMLINK_NOFOLLOW
- If Fa path names a symbolic link, the status of the symbolic link is returned.
If Fn fstatat is passed the special value AT_FDCWD in the Fa fd parameter, the current working directory is used and the behavior is identical to a call to Fn stat or Fn lstat respectively, depending on whether or not the AT_SYMLINK_NOFOLLOW bit is set in Fa flag .
The Fa sb argument is a pointer to a Vt stat structure as defined by In sys/stat.h and into which information is placed concerning the file.
The fields of Vt struct stat related to the file system are as follows:
- st_dev
- The numeric ID of the device containing the file.
- st_ino
- The file's inode number.
- st_nlink
- The number of hard links to the file.
The st_dev and st_ino fields together identify the file uniquely within the system.
The time-related fields of Vt struct stat are as follows:
- st_atim
- Time when file data last accessed. Changed by the mknod(2), utimes(2), read(2) and readv(2) system calls.
- st_mtim
- Time when file data last modified. Changed by the mkdir(2), mkfifo(2), mknod(2), utimes(2), write(2) and writev(2) system calls.
- st_ctim
- Time when file status was last changed (inode data modification). Changed by the chflags(2), chmod(2), chown(2), creat(2), link(2), mkdir(2), mkfifo(2), mknod(2), rename(2), rmdir(2), symlink(2), truncate(2), unlink(2), utimes(2), write(2) and writev(2) system calls.
- st_birthtim
- Time when the inode was created.
The following time-related macros are defined for compatibility:
#define st_atime st_atim.tv_sec #define st_mtime st_mtim.tv_sec #define st_ctime st_ctim.tv_sec #ifndef _POSIX_SOURCE #define st_birthtime st_birthtim.tv_sec #endif #ifndef _POSIX_SOURCE #define st_atimespec st_atim #define st_mtimespec st_mtim #define st_ctimespec st_ctim #define st_birthtimespec st_birthtim #endif
The size-related fields of the Vt struct stat are as follows:
- st_size
- The file size in bytes.
- st_blksize
- The optimal I/O block size for the file.
- st_blocks
- The actual number of blocks allocated for the file in 512-byte units. As short symbolic links are stored in the inode, this number may be zero.
The access-related fields of Vt struct stat are as follows:
- st_uid
- The user ID of the file's owner.
- st_gid
- The group ID of the file.
- st_mode
- Status of the file (see below).
The status information word Fa st_mode has the following bits:
#define S_IFMT 0170000 /* type of file mask */ #define S_IFIFO 0010000 /* named pipe (fifo) */ #define S_IFCHR 0020000 /* character special */ #define S_IFDIR 0040000 /* directory */ #define S_IFBLK 0060000 /* block special */ #define S_IFREG 0100000 /* regular */ #define S_IFLNK 0120000 /* symbolic link */ #define S_IFSOCK 0140000 /* socket */ #define S_IFWHT 0160000 /* whiteout */ #define S_ISUID 0004000 /* set user id on execution */ #define S_ISGID 0002000 /* set group id on execution */ #define S_ISVTX 0001000 /* save swapped text even after use */ #define S_IRWXU 0000700 /* RWX mask for owner */ #define S_IRUSR 0000400 /* read permission, owner */ #define S_IWUSR 0000200 /* write permission, owner */ #define S_IXUSR 0000100 /* execute/search permission, owner */ #define S_IRWXG 0000070 /* RWX mask for group */ #define S_IRGRP 0000040 /* read permission, group */ #define S_IWGRP 0000020 /* write permission, group */ #define S_IXGRP 0000010 /* execute/search permission, group */ #define S_IRWXO 0000007 /* RWX mask for other */ #define S_IROTH 0000004 /* read permission, other */ #define S_IWOTH 0000002 /* write permission, other */ #define S_IXOTH 0000001 /* execute/search permission, other */
For a list of access modes, see In sys/stat.h , access(2) and chmod(2). The following macros are available to test whether a st_mode value passed in the Fa m argument corresponds to a file of the specified type:
- Fn S_ISBLK m
- Test for a block special file.
- Fn S_ISCHR m
- Test for a character special file.
- Fn S_ISDIR m
- Test for a directory.
- Fn S_ISFIFO m
- Test for a pipe or FIFO special file.
- Fn S_ISLNK m
- Test for a symbolic link.
- Fn S_ISREG m
- Test for a regular file.
- Fn S_ISSOCK m
- Test for a socket.
- Fn S_ISWHT m
- Test for a whiteout.
The macros evaluate to a non-zero value if the test is true or to the value 0 if the test is false.
RETURN VALUES
Rv -stdCOMPATIBILITY
Previous versions of the system used different types for the st_dev st_uid st_gid st_rdev st_size st_blksize and st_blocks fields.ERRORS
The Fn stat and Fn lstat system calls will fail if:- Bq Er EACCES
- Search permission is denied for a component of the path prefix.
- Bq Er EFAULT
- The Fa sb or Fa path argument points to an invalid address.
- Bq Er EIO
- An I/O error occurred while reading from or writing to the file system.
- Bq Er ELOOP
- Too many symbolic links were encountered in translating the pathname.
- Bq Er ENAMETOOLONG
- A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
- Bq Er ENOENT
- The named file does not exist.
- Bq Er ENOTDIR
- A component of the path prefix is not a directory.
- Bq Er EOVERFLOW
- The file size in bytes cannot be represented correctly in the structure pointed to by Fa sb .
The Fn fstat system call will fail if:
- Bq Er EBADF
- The Fa fd argument is not a valid open file descriptor.
- Bq Er EFAULT
- The Fa sb argument points to an invalid address.
- Bq Er EIO
- An I/O error occurred while reading from or writing to the file system.
- Bq Er EOVERFLOW
- The file size in bytes cannot be represented correctly in the structure pointed to by Fa sb .
In addition to the errors returned by the Fn lstat , the Fn fstatat may fail if:
- Bq Er EBADF
- The Fa path argument does not specify an absolute path and the Fa fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
- Bq Er EINVAL
- The value of the Fa flag argument is not valid.
- Bq Er ENOTDIR
- The Fa path argument is not an absolute path and Fa fd is neither AT_FDCWD nor a file descriptor associated with a directory.