GNU/Linux man pages
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Syntaxe et mise en oeuvre :
GNU/Linux |
RedHat 6.2(Zoot) |
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fstat(2) |
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stat, fstat, lstat − get file status
#include
<sys/stat.h>
#include <unistd.h>
int
stat(const char *file_name, struct stat
*buf);
int fstat(int filedes, struct stat
*buf);
int lstat(const char *file_name, struct stat
*buf);
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.
stat stats the file pointed to by file_name and fills in buf.
lstat is identical to stat, only the link itself is stated, not the file that is obtained by tracing the links.
fstat is identical to stat, only the open file pointed to by filedes (as returned by open(2)) is stated in place of file_name.
They all return a stat structure, which contains the following fields:
struct stat
{
dev_t st_dev; /* device */
ino_t st_ino; /* inode */
mode_t st_mode; /* protection */
nlink_t st_nlink; /* number of hard links */
uid_t st_uid; /* user ID of owner */
gid_t st_gid; /* group ID of owner */
dev_t st_rdev; /* device type (if inode device) */
off_t st_size; /* total size, in bytes */
unsigned long st_blksize; /* blocksize for filesystem I/O */
unsigned long st_blocks; /* number of blocks allocated */
time_t st_atime; /* time of last access */
time_t st_mtime; /* time of last modification */
time_t st_ctime; /* time of last change */
};
The value st_blocks gives the size of the file in 512-byte blocks. The value st_blksize gives the "preferred" blocksize for efficient file system I/O. (Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.)
Not all of the Linux filesystems implement all of the time fields. Traditionally, st_atime is changed by mknod(2), utime(2), read(2), write(2), and truncate(2).
Traditionally, st_mtime is changed by mknod(2), utime(2), and write(2). The st_mtime is not changed for changes in owner, group, hard link count, or mode.
Traditionally, st_ctime is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).
The following POSIX macros are defined to check the file type:
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S_ISLNK(m) |
is it a symbolic link? |
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S_ISREG(m) |
regular file? |
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S_ISDIR(m) |
directory? |
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S_ISCHR(m) |
character device? |
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S_ISBLK(m) |
block device? |
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S_ISFIFO(m) |
fifo? |
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S_ISSOCK(m) |
socket? |
The following flags are defined for the st_mode field:
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.
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.
On success, zero is returned. On error, −1 is returned, and errno is set appropriately.
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EBADF |
filedes is bad. | ||
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ENOENT |
A component of the path file_name does not exist, or the path is an empty string. |
ENOTDIR
A component of the path is not a directory.
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ELOOP |
Too many symbolic links encountered while traversing the path. | ||
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EFAULT |
Bad address. | ||
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EACCES |
Permission denied. | ||
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ENOMEM |
Out of memory (i.e. kernel memory). |
ENAMETOOLONG
File name too long.
The stat and fstat calls conform to SVr4, SVID, POSIX, X/OPEN, BSD 4.3. The lstat call conforms to 4.3BSD and SVr4. SVr4 documents additional fstat error conditions EINTR, ENOLINK, and EOVERFLOW. SVr4 documents additional stat and lstat error conditions EACCES, EINTR, EMULTIHOP, ENOLINK, and EOVERFLOW. 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.)
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. Unix V7 (and later systems) had S_IREAD, S_IWRITE, S_IEXEC, where POSIX prescribes the synonyms S_IRUSR, S_IWUSR, S_IXUSR.
Values that have been (or are) in use on various systems:
A sticky command appeared in Version 32V AT&T UNIX.
chmod(2), chown(2), readlink(2), utime(2)
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fstat(2) | |