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diff --git a/man7/inode.7 b/man7/inode.7 deleted file mode 100644 index 7054fe8..0000000 --- a/man7/inode.7 +++ /dev/null @@ -1,480 +0,0 @@ -'\" t -.\" Copyright (c) 2017 Michael Kerrisk <mtk.manpages@gmail.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.TH inode 7 2023-10-31 "Linux man-pages 6.7" -.SH NAME -inode \- file inode information -.SH DESCRIPTION -Each file has an inode containing metadata about the file. -An application can retrieve this metadata using -.BR stat (2) -(or related calls), which returns a -.I stat -structure, or -.BR statx (2), -which returns a -.I statx -structure. -.P -The following is a list of the information typically found in, -or associated with, the file inode, -with the names of the corresponding structure fields returned by -.BR stat (2) -and -.BR statx (2): -.TP -Device where inode resides -\fIstat.st_dev\fP; \fIstatx.stx_dev_minor\fP and \fIstatx.stx_dev_major\fP -.IP -Each inode (as well as the associated file) resides in a filesystem -that is hosted on a device. -That device is identified by the combination of its major ID -(which identifies the general class of device) -and minor ID (which identifies a specific instance in the general class). -.TP -Inode number -\fIstat.st_ino\fP; \fIstatx.stx_ino\fP -.IP -Each file in a filesystem has a unique inode number. -Inode numbers are guaranteed to be unique only within a filesystem -(i.e., the same inode numbers may be used by different filesystems, -which is the reason that hard links may not cross filesystem boundaries). -This field contains the file's inode number. -.TP -File type and mode -\fIstat.st_mode\fP; \fIstatx.stx_mode\fP -.IP -See the discussion of file type and mode, below. -.TP -Link count -\fIstat.st_nlink\fP; \fIstatx.stx_nlink\fP -.IP -This field contains the number of hard links to the file. -Additional links to an existing file are created using -.BR link (2). -.TP -User ID -\fIstat.st_uid\fP; \fIstatx.stx_uid\fP -.IP -This field records the user ID of the owner of the file. -For newly created files, -the file user ID is the effective user ID of the creating process. -The user ID of a file can be changed using -.BR chown (2). -.TP -Group ID -\fIstat.st_gid\fP; \fIstatx.stx_gid\fP -.IP -The inode records the ID of the group owner of the file. -For newly created files, -the file group ID is either the group ID of the parent directory or -the effective group ID of the creating process, -depending on whether or not the set-group-ID bit -is set on the parent directory (see below). -The group ID of a file can be changed using -.BR chown (2). -.TP -Device represented by this inode -\fIstat.st_rdev\fP; \fIstatx.stx_rdev_minor\fP and \fIstatx.stx_rdev_major\fP -.IP -If this file (inode) represents a device, -then the inode records the major and minor ID of that device. -.TP -File size -\fIstat.st_size\fP; \fIstatx.stx_size\fP -.IP -This field gives the size of the file (if it is a regular -file or a symbolic link) in bytes. -The size of a symbolic link is the length of the pathname -it contains, without a terminating null byte. -.TP -Preferred block size for I/O -\fIstat.st_blksize\fP; \fIstatx.stx_blksize\fP -.IP -This field gives the "preferred" blocksize for efficient filesystem I/O. -(Writing to a file in smaller chunks may cause -an inefficient read-modify-rewrite.) -.TP -Number of blocks allocated to the file -\fIstat.st_blocks\fP; \fIstatx.stx_blocks\fP -.IP -This field indicates the number of blocks allocated to the file, -512-byte units, -(This may be smaller than -.IR st_size /512 -when the file has holes.) -.IP -The POSIX.1 standard notes -.\" Rationale for sys/stat.h in POSIX.1-2008 -that the unit for the -.I st_blocks -member of the -.I stat -structure is not defined by the standard. -On many implementations it is 512 bytes; -on a few systems, a different unit is used, such as 1024. -Furthermore, the unit may differ on a per-filesystem basis. -.TP -Last access timestamp (atime) -\fIstat.st_atime\fP; \fIstatx.stx_atime\fP -.IP -This is the file's last access timestamp. -It is changed by file accesses, for example, by -.BR execve (2), -.BR mknod (2), -.BR pipe (2), -.BR utime (2), -and -.BR read (2) -(of more than zero bytes). -Other interfaces, such as -.BR mmap (2), -may or may not update the atime timestamp -.IP -Some filesystem types allow mounting in such a way that file -and/or directory accesses do not cause an update of the atime timestamp. -(See -.IR noatime , -.IR nodiratime , -and -.I relatime -in -.BR mount (8), -and related information in -.BR mount (2).) -In addition, the atime timestamp -is not updated if a file is opened with the -.B O_NOATIME -flag; see -.BR open (2). -.TP -File creation (birth) timestamp (btime) -(not returned in the \fIstat\fP structure); \fIstatx.stx_btime\fP -.IP -The file's creation timestamp. -This is set on file creation and not changed subsequently. -.IP -The btime timestamp was not historically present on UNIX systems -and is not currently supported by most Linux filesystems. -.\" FIXME Is it supported on ext4 and XFS? -.TP -Last modification timestamp (mtime) -\fIstat.st_mtime\fP; \fIstatx.stx_mtime\fP -.IP -This is the file's last modification timestamp. -It is changed by file modifications, for example, by -.BR mknod (2), -.BR truncate (2), -.BR utime (2), -and -.BR write (2) -(of more than zero bytes). -Moreover, the mtime timestamp -of a directory is changed by the creation or deletion of files -in that directory. -The mtime timestamp is -.I not -changed for changes in owner, group, hard link count, or mode. -.TP -Last status change timestamp (ctime) -\fIstat.st_ctime\fP; \fIstatx.stx_ctime\fP -.IP -This is the file's last status change timestamp. -It is changed by writing or by setting inode information -(i.e., owner, group, link count, mode, etc.). -.P -The timestamp fields report time measured with a zero point at the -.IR Epoch , -1970-01-01 00:00:00 +0000, UTC (see -.BR time (7)). -.P -Nanosecond timestamps are supported on XFS, JFS, Btrfs, and -ext4 (since Linux 2.6.23). -.\" commit ef7f38359ea8b3e9c7f2cae9a4d4935f55ca9e80 -Nanosecond timestamps are not supported in ext2, ext3, and Reiserfs. -In order to return timestamps with nanosecond precision, -the timestamp fields in the -.I stat -and -.I statx -structures are defined as structures that include a nanosecond component. -See -.BR stat (2) -and -.BR statx (2) -for details. -On filesystems that do not support subsecond timestamps, -the nanosecond fields in the -.I stat -and -.I statx -structures are returned with the value 0. -.\" -.SS The file type and mode -The -.I stat.st_mode -field (for -.BR statx (2), -the -.I statx.stx_mode -field) contains the file type and mode. -.P -POSIX refers to the -.I stat.st_mode -bits corresponding to the mask -.B S_IFMT -(see below) as the -.IR "file type" , -the 12 bits corresponding to the mask 07777 as the -.I file mode bits -and the least significant 9 bits (0777) as the -.IR "file permission bits" . -.P -The following mask values are defined for the file type: -.in +4n -.TS -lB l l. -S_IFMT 0170000 bit mask for the file type bit field - -S_IFSOCK 0140000 socket -S_IFLNK 0120000 symbolic link -S_IFREG 0100000 regular file -S_IFBLK 0060000 block device -S_IFDIR 0040000 directory -S_IFCHR 0020000 character device -S_IFIFO 0010000 FIFO -.TE -.in -.P -Thus, to test for a regular file (for example), one could write: -.P -.in +4n -.EX -stat(pathname, &sb); -if ((sb.st_mode & S_IFMT) == S_IFREG) { - /* Handle regular file */ -} -.EE -.in -.P -Because tests of the above form are common, additional -macros are defined by POSIX to allow the test of the file type in -.I st_mode -to be written more concisely: -.RS 4 -.TP 1.2i -.BR S_ISREG (m) -is it a regular file? -.TP -.BR S_ISDIR (m) -directory? -.TP -.BR S_ISCHR (m) -character device? -.TP -.BR S_ISBLK (m) -block device? -.TP -.BR S_ISFIFO (m) -FIFO (named pipe)? -.TP -.BR S_ISLNK (m) -symbolic link? (Not in POSIX.1-1996.) -.TP -.BR S_ISSOCK (m) -socket? (Not in POSIX.1-1996.) -.RE -.P -The preceding code snippet could thus be rewritten as: -.P -.in +4n -.EX -stat(pathname, &sb); -if (S_ISREG(sb.st_mode)) { - /* Handle regular file */ -} -.EE -.in -.P -The definitions of most of the above file type test macros -are provided if any of the following feature test macros is defined: -.B _BSD_SOURCE -(in glibc 2.19 and earlier), -.B _SVID_SOURCE -(in glibc 2.19 and earlier), -or -.B _DEFAULT_SOURCE -(in glibc 2.20 and later). -In addition, definitions of all of the above macros except -.B S_IFSOCK -and -.BR S_ISSOCK () -are provided if -.B _XOPEN_SOURCE -is defined. -.P -The definition of -.B S_IFSOCK -can also be exposed either by defining -.B _XOPEN_SOURCE -with a value of 500 or greater or (since glibc 2.24) by defining both -.B _XOPEN_SOURCE -and -.BR _XOPEN_SOURCE_EXTENDED . -.P -The definition of -.BR S_ISSOCK () -is exposed if any of the following feature test macros is defined: -.B _BSD_SOURCE -(in glibc 2.19 and earlier), -.B _DEFAULT_SOURCE -(in glibc 2.20 and later), -.B _XOPEN_SOURCE -with a value of 500 or greater, -.B _POSIX_C_SOURCE -with a value of 200112L or greater, or (since glibc 2.24) by defining both -.B _XOPEN_SOURCE -and -.BR _XOPEN_SOURCE_EXTENDED . -.P -The following mask values are defined for -the file mode component of the -.I st_mode -field: -.in +4n -.TS -lB l lx. -S_ISUID 04000 T{ -set-user-ID bit (see \fBexecve\fP(2)) -T} -S_ISGID 02000 T{ -set-group-ID bit (see below) -T} -S_ISVTX 01000 T{ -sticky bit (see below) -T} - -S_IRWXU 00700 T{ -owner has read, write, and execute permission -T} -S_IRUSR 00400 T{ -owner has read permission -T} -S_IWUSR 00200 T{ -owner has write permission -T} -S_IXUSR 00100 T{ -owner has execute permission -T} - -S_IRWXG 00070 T{ -group has read, write, and execute permission -T} -S_IRGRP 00040 T{ -group has read permission -T} -S_IWGRP 00020 T{ -group has write permission -T} -S_IXGRP 00010 T{ -group has execute permission -T} - -S_IRWXO 00007 T{ -others (not in group) have read, write, and execute permission -T} -S_IROTH 00004 T{ -others have read permission -T} -S_IWOTH 00002 T{ -others have write permission -T} -S_IXOTH 00001 T{ -others have execute permission -T} -.TE -.in -.P -The set-group-ID bit -.RB ( S_ISGID ) -has several special uses. -For a directory, it indicates that BSD semantics are to be used -for that directory: files created there inherit their group ID from -the directory, not from the effective group ID of the creating process, -and directories created there will also get the -.B S_ISGID -bit set. -For an executable file, the set-group-ID bit causes the effective group ID -of a process that executes the file to change as described in -.BR execve (2). -For a file that does not have the group execution bit -.RB ( S_IXGRP ) -set, -the set-group-ID bit indicates mandatory file/record locking. -.P -The sticky bit -.RB ( 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 a privileged -process. -.SH STANDARDS -POSIX.1-2008. -.SH HISTORY -POSIX.1-2001. -.P -POSIX.1-1990 did not describe the -.BR S_IFMT , -.BR S_IFSOCK , -.BR S_IFLNK , -.BR S_IFREG , -.BR S_IFBLK , -.BR S_IFDIR , -.BR S_IFCHR , -.BR S_IFIFO , -and -.B S_ISVTX -constants, but instead specified the use of -the macros -.BR S_ISDIR () -and so on. -.P -The -.BR S_ISLNK () -and -.BR S_ISSOCK () -macros were not in -POSIX.1-1996; -the former is from SVID 4, the latter from SUSv2. -.P -UNIX\ V7 (and later systems) had -.BR S_IREAD , -.BR S_IWRITE , -.BR S_IEXEC , -and -where POSIX -prescribes the synonyms -.BR S_IRUSR , -.BR S_IWUSR , -and -.BR S_IXUSR . -.SH NOTES -For pseudofiles that are autogenerated by the kernel, the file size -(\fIstat.st_size\fP; \fIstatx.stx_size\fP) -reported by the kernel is not accurate. -For example, the value 0 is returned for many files under the -.I /proc -directory, -while various files under -.I /sys -report a size of 4096 bytes, even though the file content is smaller. -For such files, one should simply try to read as many bytes as possible -(and append \[aq]\e0\[aq] to the returned buffer -if it is to be interpreted as a string). -.SH SEE ALSO -.BR stat (1), -.BR stat (2), -.BR statx (2), -.BR symlink (7) |