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Annotated edit history of lstat(2) version 2, including all changes. View license author blame.
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1 perry 1 !!NAME
2 PerryLorier 2 fstat - get file status
1 perry 3 !!SYNOPSIS
2 PerryLorier 4 __#include <sys/types.h>__
5 __#include <sys/stat.h>__
6 __#include <unistd.h>__
1 perry 7
2 PerryLorier 8 __int lstat(const char *__''file_name''__, struct stat *__''buf''__);__
1 perry 9
10 !!DESCRIPTION
11
2 PerryLorier 12 These functions return information about the specified file. You do not need any access rights to the file to get this information but you need search rights to all directories named in the path leading to the file.
1 perry 13
2 PerryLorier 14 lstat(2) takes the metadata of the filename ''file_name'' and places that information in the structure ''buf'' which contains the following elements:
1 perry 15
2 PerryLorier 16 struct stat {
17 dev_t st_dev; /* device */
18 ino_t st_ino; /* inode */
19 mode_t st_mode; /* protection */
20 nlink_t st_nlink; /* number of hard links */
21 uid_t st_uid; /* user ID of owner */
22 gid_t st_gid; /* group ID of owner */
23 dev_t st_rdev; /* device type (if inode device) */
24 off_t st_size; /* total size, in bytes */
25 unsigned long st_blksize; /* blocksize for filesystem I/O */
26 unsigned long st_blocks; /* number of blocks allocated */
27 time_t st_atime; /* time of last access */
28 time_t st_mtime; /* time of last modification */
29 time_t st_ctime; /* time of last change */
30 };
1 perry 31
2 PerryLorier 32 The value ''st_size'' gives the size of the file (if it is a regular file or a symlink) in bytes. The size of a symlink is the length of the pathname it contains, without trailing NUL.
1 perry 33
2 PerryLorier 34 The value ''st_blocks'' gives the size of the file in 512-byte blocks. (This may be smaller than ''st_size''/512 e.g. when the file has holes.) The value ''st_blksize'' gives the ''
1 perry 35
2 PerryLorier 36 Not all of the Linux filesystems implement all of the time fields. Some file system types allow mounting in such a way that file accesses do not cause an update of the ''st_atime'' field. (See `noatime' in
1 perry 37 mount(8).)
38
2 PerryLorier 39 The field ''st_atime'' is changed by file accesses, e.g. by execve(2), mknod(2), pipe(2), utime(2) and read(2) (of more than zero bytes). Other routines, like mmap(2), may or may not update ''st_atime''.
1 perry 40
2 PerryLorier 41 The field ''st_mtime'' is changed by file modifications, e.g. by mknod(2), truncate(2), utime(2) and write(2) (of more than zero bytes). Moreover, ''st_mtime'' of a directory is changed by the creation or deletion of files in that directory. The ''st_mtime'' field is ''not'' changed for changes in owner, group, hard link count, or mode.
1 perry 42
2 PerryLorier 43 The field ''st_ctime'' is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).
1 perry 44
2 PerryLorier 45 The following POSIX macros are defined to check the file type:
1 perry 46
2 PerryLorier 47 ;S_ISREG(m): is it a regular file?
48 ;S_ISDIR(m): directory?
49 ;S_ISCHR(m): character device?
50 ;S_ISBLK(m): block device?
51 ;S_ISFIFO(m): fifo?
52 ;S_ISLNK(m): symbolic link? (Not in POSIX.1-1996.)
53 ;S_ISSOCK(m): socket? (Not in POSIX.1-1996.)
1 perry 54
2 PerryLorier 55 The following flags are defined for the ''st_mode'' field:
1 perry 56
2 PerryLorier 57 |S_IFMT|0170000|bitmask for the file type bitfields
58 |S_IFSOCK|0140000|socket
59 |S_IFLNK|0120000|SymbolicLink
60 |S_IFREG|0100000|regular file
61 |S_IFBLK|0060000|BlockDevice
62 |S_IFDIR|0040000|directory
63 |S_IFCHR|0020000|CharacterDevice
64 |S_IFIFO|0010000|NamedFifo
65 |S_ISUID|0004000|set UID bit
66 |S_ISGID|0002000|set GID bit (see below)
67 |S_ISVTX|0001000|sticky bit (see below)
68 |S_IRWXU|00700|mask for file owner permissions
69 |S_IRUSR|00400|owner has read permission
70 |S_IWUSR|00200|owner has write permission
71 |S_IXUSR|00100|owner has execute permission
72 |S_IRWXG|00070|mask for group permissions
73 |S_IRGRP|00040|group has read permission
74 |S_IWGRP|00020|group has write permission
75 |S_IXGRP|00010|group has execute permission
76 |S_IRWXO|00007|mask for permissions for others (not in group)
77 |S_IROTH|00004|others have read permission
78 |S_IWOTH|00002|others have write permisson
79 |S_IXOTH|00001|others have execute permission
1 perry 80
81 The set GID bit (S_ISGID) has several special uses: For a directory it indicates that BSD semantics is to be used for that directory: files created there inherit their group ID from the directory, not from the effective gid of the creating process, and directories created there will also get the S_ISGID bit set. For a file that does not have the group execution bit (S_IXGRP) set, it indicates mandatory file/record locking.
82
2 PerryLorier 83 The `sticky' bit (S_ISVTX) on a directory means that a file in that directory can be renamed or deleted only by the owner of the file, by the owner of the directory, and by root.
1 perry 84
85 !!RETURN VALUE
2 PerryLorier 86 On success, zero is returned. On error, -1 is returned, and ''errno'' is set appropriately.
1 perry 87
88 !!ERRORS
2 PerryLorier 89 ;[EBADF]: ''filedes'' is bad.
90 ;[ENOENT]: A component of the path ''file_name'' does not exist, or the path is an empty string.
91 ;[ENOTDIR]: A component of the path is not a directory.
92 ;[ELOOP]: Too many symbolic links encountered while traversing the path.
93 ;[EFAULT]: Bad address.
94 ;[EACCES]: Permission denied.
95 ;[ENOMEM]: Out of memory (i.e. kernel memory).
1 perry 96
97 !!CONFORMING TO
98
2 PerryLorier 99 The fstat(2) calls conform to SVr4, SVID, POSIX, X/OPEN, BSD 4.3. SVr4 documents additional fstat(2) error conditions [EINTR], [ENOLINK], and [EOVERFLOW].
1 perry 100
2 PerryLorier 101 Use of the ''st_blocks'' and ''st_blksize'' fields may be less portable. (They were introduced in BSD. Are not specified by POSIX. The interpretation differs between systems, and possibly on a single system when NFS mounts are involved.)
1 perry 102
2 PerryLorier 103 POSIX does not describe the S_IFMT, S_IFSOCK, S_IFLNK, S_IFREG, S_IFBLK, S_IFDIR, S_IFCHR, S_IFIFO, S_ISVTX bits, but instead demands the use of the macros S_ISDIR(), etc. The S_ISLNK and S_ISSOCK macros are not in POSIX.1-1996, but both will be in the next POSIX standard; the former is from SVID 4v2, the latter from SUSv2.
1 perry 104
2 PerryLorier 105 Unix V7 (and later systems) had S_IREAD, S_IWRITE, S_IEXEC, where POSIX prescribes the synonyms S_IRUSR, S_IWUSR, S_IXUSR.
1 perry 106
107 !!OTHER SYSTEMS
2 PerryLorier 108 Values that have been (or are) in use on various systems:
1 perry 109
2 PerryLorier 110 |^__hex__|^__name__|^__ls__|^__octal__|^__description__
111 |f000|S_IFMT| |170000|mask for file type
112 |0000|| |000000|SCO out-of-service inode, BSD unknown type, SVID-v2 and XPG2 have both 0 and 0100000 for ordinary file
113 |1000|S_IFIFO|p (pipe symbol)|010000|fifo (named pipe)
114 |2000|S_IFCHR|c|020000|character special (V7)
115 |3000|S_IFMPC| |030000|multiplexed character special (V7)
116 |4000|S_IFDIR|d/|040000|directory (V7)
117 |5000|S_IFNAM| |050000|XENIX named special file with two subtypes, distinguished by st_rdev values 1, 2:
118 |0001|S_INSEM|s|000001|XENIX semaphore subtype of IFNAM
119 |0002|S_INSHD|m|000002|XENIX shared data subtype of IFNAM
120 |6000|S_IFBLK|b|060000|block special (V7)
121 |7000|S_IFMPB| |070000|multiplexed block special (V7)
122 |8000|S_IFREG|-|100000|regular (V7)
123 |9000|S_IFCMP| |110000|VxFS compressed
124 |9000|S_IFNWK|n|110000|network special (HP-UX)
125 |a000|S_IFLNK|l@|120000|symbolic link (BSD)
126 |b000|S_IFSHAD| |130000|Solaris shadow inode for ACL (not seen by userspace)
127 |c000|S_IFSOCK|s=|140000|socket (BSD; also "S_IFSOC" on VxFS)
128 |d000|S_IFDOOR|D>|150000|Solaris door
129 |e000|S_IFWHT|w%|160000|BSD whiteout (not used for inode)
130 |0200|S_ISVTX| |001000|`sticky bit': save swapped text even after use (V7), reserved (SVID-v2), On non-directories: don't cache this file (SunOS), On directories: restricted deletion flag (SVID-v4.2)
131 |0400|S_ISGID| |002000|set group ID on execution (V7), for directories: use BSD semantics for propagation of gid
132 |0400|S_ENFMT| |002000|SysV file locking enforcement (shared w/ S_ISGID)
133 |0800|S_ISUID| |004000|set user ID on execution (V7)
134 |0800|S_CDF| |004000|directory is a context dependent file (HP-UX)
1 perry 135
136
137 A sticky command appeared in Version 32V AT
138
139
2 PerryLorier 140
141 !!SEE ALSO
142 chmod(2), chown(2), readlink(2), utime(2), fstatfs(2), stat(2), lstat(2)
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