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Annotated edit history of fstat(2) version 9, including all changes. View license author blame.
Rev Author # Line
1 perry 1 !!NAME
2 PerryLorier 2 fstat - get file status
1 perry 3 !!SYNOPSIS
3 PerryLorier 4 __#include <sys/types.h>__
5 __#include <sys/stat.h>__
6 __#include <unistd.h>__
1 perry 7
3 PerryLorier 8 __int fstat(int__ ''filedes''__, struct stat *__''buf''__);__
1 perry 9 !!DESCRIPTION
10
2 PerryLorier 11 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 12
2 PerryLorier 13 fstat(2) takes the metadata of the file opened with ''filedes'' and places that information in the structure ''buf' which contains the following elements:
1 perry 14
2 PerryLorier 15 struct stat {
16 dev_t st_dev; /* device */
17 ino_t st_ino; /* inode */
18 mode_t st_mode; /* protection */
19 nlink_t st_nlink; /* number of hard links */
20 uid_t st_uid; /* user ID of owner */
21 gid_t st_gid; /* group ID of owner */
22 dev_t st_rdev; /* device type (if inode device) */
23 off_t st_size; /* total size, in bytes */
24 unsigned long st_blksize; /* blocksize for filesystem I/O */
25 unsigned long st_blocks; /* number of blocks allocated */
26 time_t st_atime; /* time of last access */
27 time_t st_mtime; /* time of last modification */
28 time_t st_ctime; /* time of last change */
29 };
1 perry 30
2 PerryLorier 31 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 32
2 PerryLorier 33 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 34
2 PerryLorier 35 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 36 mount(8).)
37
4 PerryLorier 38 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 39
2 PerryLorier 40 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 41
2 PerryLorier 42 The field ''st_ctime'' is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).
1 perry 43
2 PerryLorier 44 The following POSIX macros are defined to check the file type:
1 perry 45
2 PerryLorier 46 ;S_ISREG(m): is it a regular file?
47 ;S_ISDIR(m): directory?
48 ;S_ISCHR(m): character device?
49 ;S_ISBLK(m): block device?
50 ;S_ISFIFO(m): fifo?
51 ;S_ISLNK(m): symbolic link? (Not in POSIX.1-1996.)
52 ;S_ISSOCK(m): socket? (Not in POSIX.1-1996.)
1 perry 53
2 PerryLorier 54 The following flags are defined for the ''st_mode'' field:
5 PerryLorier 55
56 |S_IFMT|0170000|bitmask for the file type bitfields
57 |S_IFSOCK|0140000|socket
58 |S_IFLNK|0120000|SymbolicLink
59 |S_IFREG|0100000|regular file
60 |S_IFBLK|0060000|BlockDevice
61 |S_IFDIR|0040000|directory
62 |S_IFCHR|0020000|CharacterDevice
63 |S_IFIFO|0010000|NamedFifo
64 |S_ISUID|0004000|set UID bit
65 |S_ISGID|0002000|set GID bit (see below)
66 |S_ISVTX|0001000|sticky bit (see below)
67 |S_IRWXU|00700|mask for file owner permissions
68 |S_IRUSR|00400|owner has read permission
69 |S_IWUSR|00200|owner has write permission
70 |S_IXUSR|00100|owner has execute permission
71 |S_IRWXG|00070|mask for group permissions
72 |S_IRGRP|00040|group has read permission
73 |S_IWGRP|00020|group has write permission
74 |S_IXGRP|00010|group has execute permission
75 |S_IRWXO|00007|mask for permissions for others (not in group)
76 |S_IROTH|00004|others have read permission
77 |S_IWOTH|00002|others have write permisson
78 |S_IXOTH|00001|others have execute permission
1 perry 79
80 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.
81
2 PerryLorier 82 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 83
84 !!RETURN VALUE
2 PerryLorier 85 On success, zero is returned. On error, -1 is returned, and ''errno'' is set appropriately.
1 perry 86
87 !!ERRORS
2 PerryLorier 88 ;[EBADF]: ''filedes'' is bad.
89 ;[ENOENT]: A component of the path ''file_name'' does not exist, or the path is an empty string.
90 ;[ENOTDIR]: A component of the path is not a directory.
91 ;[ELOOP]: Too many symbolic links encountered while traversing the path.
92 ;[EFAULT]: Bad address.
93 ;[EACCES]: Permission denied.
94 ;[ENOMEM]: Out of memory (i.e. kernel memory).
95
1 perry 96 !!CONFORMING TO
97
2 PerryLorier 98 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 99
2 PerryLorier 100 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 101
2 PerryLorier 102 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 103
2 PerryLorier 104 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 105
106 !!OTHER SYSTEMS
2 PerryLorier 107 Values that have been (or are) in use on various systems:
5 PerryLorier 108
109 |^__hex__|^__name__|^__ls__|^__octal__|^__description__
110 |f000|S_IFMT| |170000|mask for file type
111 |0000|| |000000|SCO out-of-service inode, BSD unknown type, SVID-v2 and XPG2 have both 0 and 0100000 for ordinary file
112 |1000|S_IFIFO|p (pipe symbol)|010000|fifo (named pipe)
113 |2000|S_IFCHR|c|020000|character special (V7)
114 |3000|S_IFMPC| |030000|multiplexed character special (V7)
115 |4000|S_IFDIR|d/|040000|directory (V7)
116 |5000|S_IFNAM| |050000|XENIX named special file with two subtypes, distinguished by st_rdev values 1, 2:
117 |0001|S_INSEM|s|000001|XENIX semaphore subtype of IFNAM
118 |0002|S_INSHD|m|000002|XENIX shared data subtype of IFNAM
119 |6000|S_IFBLK|b|060000|block special (V7)
120 |7000|S_IFMPB| |070000|multiplexed block special (V7)
121 |8000|S_IFREG|-|100000|regular (V7)
122 |9000|S_IFCMP| |110000|VxFS compressed
123 |9000|S_IFNWK|n|110000|network special (HP-UX)
124 |a000|S_IFLNK|l@|120000|symbolic link (BSD)
125 |b000|S_IFSHAD| |130000|Solaris shadow inode for ACL (not seen by userspace)
126 |c000|S_IFSOCK|s=|140000|socket (BSD; also "S_IFSOC" on VxFS)
127 |d000|S_IFDOOR|D>|150000|Solaris door
128 |e000|S_IFWHT|w%|160000|BSD whiteout (not used for inode)
129 |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)
130 |0400|S_ISGID| |002000|set group ID on execution (V7), for directories: use BSD semantics for propagation of gid
131 |0400|S_ENFMT| |002000|SysV file locking enforcement (shared w/ S_ISGID)
132 |0800|S_ISUID| |004000|set user ID on execution (V7)
133 |0800|S_CDF| |004000|directory is a context dependent file (HP-UX)
134
1 perry 135
136 A sticky command appeared in Version 32V AT
6 PerryLorier 137
138 !!EXAMPLE
139
140 /* fstat(2)'s a file, and displays the results
141 *
142 */
143
144 #include <sys/stat.h> /* for struct stat, fstat(2), S_* constants */
145 #include <sys/types.h>/* for mode_t, uid_t, etc... */
146 #include <errno.h> /* for errno */
147 #include <fcntl.h> /* for open(2), O_* */
148 #include <pwd.h> /* for getpwuid(3) */
149 #include <string.h> /* for strerror(3) */
150 #include <stdio.h> /* for printf(3) etc */
151 #include <time.h> /* for asctime(3) */
152 #include <unistd.h> /* for close(2) */
153
154 int do_stat(char *filename)
155 {
156 int fd;
157 struct stat statbuf;
158
159 fd = open(filename,O_RDONLY);
160
161 if (fd == -1) {
162 printf("fstat: open(\"%s\",O_RDONLY): %s (%i)",
163 filename,
164 strerror(errno),
165 errno);
166 return 1;
167 }
168
169 if (fstat(fd,&statbuf) == -1) {
170 printf("fstat: fstat: %s (%i)",
171 strerror(errno),
172 errno);
173 return 1;
174 }
175
176 if (S_ISREG(statbuf.st_mode)) printf("Regular file");
177 else if (S_ISDIR(statbuf.st_mode)) printf("Directory");
178 else if (S_ISCHR(statbuf.st_mode)) printf("Character Device");
179 else if (S_ISBLK(statbuf.st_mode)) printf("Block Device");
180 else if (S_ISFIFO(statbuf.st_mode)) printf("Fifo");
181 else if (S_ISLNK(statbuf.st_mode)) printf("Symbolic Link");
182 else if (S_ISSOCK(statbuf.st_mode)) printf("Socket");
183 printf(": \"%s\"\n",filename);
8 PerryLorier 184 printf("Size: %-20i Blocks: %-10i Block Size: %-10i\n",
6 PerryLorier 185 (int)statbuf.st_size,
186 (int)statbuf.st_blocks,
187 (int)statbuf.st_blksize);
8 PerryLorier 188 printf("Device: 0x%06llx (%7llu) Inode: %-10li Links: %i\n",
6 PerryLorier 189 statbuf.st_dev,
190 statbuf.st_dev,
191 statbuf.st_ino,
192 statbuf.st_nlink);
8 PerryLorier 193 printf("Access: %c%c%c%c%c%c%c%c%c (0%-5o) User ID: %i(%s) Group ID: %i(%s)\n",
194 statbuf.st_mode & S_IRUSR ? 'r' : '-',
195 statbuf.st_mode & S_IWUSR ? 'w' : '-',
196 statbuf.st_mode & S_ISUID ? (
197 statbuf.st_mode & S_IXUSR ? 's' : 'S'
198 ) : (
199 statbuf.st_mode & S_IXUSR ? 'x' : '-'
200 ),
201 statbuf.st_mode & S_IRGRP ? 'r' : '-',
202 statbuf.st_mode & S_IWGRP ? 'w' : '-',
203 statbuf.st_mode & S_ISGID ? (
204 statbuf.st_mode & S_IXGRP ? 's' : 'S'
205 ) : (
206 statbuf.st_mode & S_IXGRP ? 'x' : '-'
207 ),
208 statbuf.st_mode & S_IROTH ? 'r' : '-',
209 statbuf.st_mode & S_IWOTH ? 'w' : '-',
210 statbuf.st_mode & S_ISVTX ? (
211 statbuf.st_mode & S_IXGRP ? 't' : 'T'
212 ) : (
213 statbuf.st_mode & S_IXGRP ? 'x' : '-'
214 ),
215 statbuf.st_mode,
6 PerryLorier 216 statbuf.st_uid,getpwuid(statbuf.st_uid)->pw_name,
217 statbuf.st_gid,getpwuid(statbuf.st_gid)->pw_name);
218 printf("Access Time: %s", ctime(&statbuf.st_atime));
219 printf("Modify Time: %s", ctime(&statbuf.st_mtime));
220 printf("Change Time: %s", ctime(&statbuf.st_ctime));
221
222 if (close(fd) == -1) {
223 printf("fstat: close(fd): %s (%i)",
224 strerror(errno),
225 errno);
226 return 1;
227 }
228
229 return 0;
230 }
231
232 int main(int argc, char **argv)
233 {
234 int i;
235
236 if (argc<2) {
7 PerryLorier 237 printf("%s: too few arguments\n",argv[[0]);
238 printf("usage: %s filename...\n",argv[[0]);
6 PerryLorier 239 return 1;
240 }
241 for (i=1;i<argc;i++) {
7 PerryLorier 242 do_stat(argv[[i]);
6 PerryLorier 243 }
244 return 0;
245 }
246
1 perry 247 !!SEE ALSO
9 PerryLorier 248 chmod(2), chown(2), readlink(2), utime(2), fstatfs(2), stat(2)
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