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diff --git a/man2/stat.2 b/man2/stat.2 new file mode 100644 index 0000000..f41daab --- /dev/null +++ b/man2/stat.2 @@ -0,0 +1,539 @@ +.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 +.\" Parts Copyright (c) 1995 Nicolai Langfeldt (janl@ifi.uio.no), 1/1/95 +.\" and Copyright (c) 2006, 2007, 2014 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" Modified by Michael Haardt <michael@moria.de> +.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu> +.\" Modified 1995-05-18 by Todd Larason <jtl@molehill.org> +.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com> +.\" Modified 1995-01-09 by Richard Kettlewell <richard@greenend.org.uk> +.\" Modified 1998-05-13 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de> +.\" Modified 1999-07-06 by aeb & Albert Cahalan +.\" Modified 2000-01-07 by aeb +.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com> +.\" 2007-06-08 mtk: Added example program +.\" 2007-07-05 mtk: Added details on underlying system call interfaces +.\" +.TH stat 2 2023-05-03 "Linux man-pages 6.05.01" +.SH NAME +stat, fstat, lstat, fstatat \- get file status +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/stat.h> +.PP +.BI "int stat(const char *restrict " pathname , +.BI " struct stat *restrict " statbuf ); +.BI "int fstat(int " fd ", struct stat *" statbuf ); +.BI "int lstat(const char *restrict " pathname , +.BI " struct stat *restrict " statbuf ); +.PP +.BR "#include <fcntl.h> " "/* Definition of " AT_* " constants */" +.B #include <sys/stat.h> +.PP +.BI "int fstatat(int " dirfd ", const char *restrict " pathname , +.BI " struct stat *restrict " statbuf ", int " flags ); +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.BR lstat (): +.nf + /* Since glibc 2.20 */ _DEFAULT_SOURCE + || _XOPEN_SOURCE >= 500 +.\" _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED + || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L + || /* glibc 2.19 and earlier */ _BSD_SOURCE +.fi +.PP +.BR fstatat (): +.nf + Since glibc 2.10: + _POSIX_C_SOURCE >= 200809L + Before glibc 2.10: + _ATFILE_SOURCE +.fi +.SH DESCRIPTION +These functions return information about a file, in the buffer pointed to by +.IR statbuf . +No permissions are required on the file itself, but\[em]in the case of +.BR stat (), +.BR fstatat (), +and +.BR lstat ()\[em]execute +(search) permission is required on all of the directories in +.I pathname +that lead to the file. +.PP +.BR stat () +and +.BR fstatat () +retrieve information about the file pointed to by +.IR pathname ; +the differences for +.BR fstatat () +are described below. +.PP +.BR lstat () +is identical to +.BR stat (), +except that if +.I pathname +is a symbolic link, then it returns information about the link itself, +not the file that the link refers to. +.PP +.BR fstat () +is identical to +.BR stat (), +except that the file about which information is to be retrieved +is specified by the file descriptor +.IR fd . +.\" +.SS The stat structure +All of these system calls return a +.I stat +structure (see +.BR stat (3type)). +.PP +.\" Background: inode attributes are modified with i_mutex held, but +.\" read by stat() without taking the mutex. +.IR Note : +for performance and simplicity reasons, different fields in the +.I stat +structure may contain state information from different moments +during the execution of the system call. +For example, if +.I st_mode +or +.I st_uid +is changed by another process by calling +.BR chmod (2) +or +.BR chown (2), +.BR stat () +might return the old +.I st_mode +together with the new +.IR st_uid , +or the old +.I st_uid +together with the new +.IR st_mode . +.SS fstatat() +The +.BR fstatat () +system call is a more general interface for accessing file information +which can still provide exactly the behavior of each of +.BR stat (), +.BR lstat (), +and +.BR fstat (). +.PP +If the pathname given in +.I pathname +is relative, then it is interpreted relative to the directory +referred to by the file descriptor +.I dirfd +(rather than relative to the current working directory of +the calling process, as is done by +.BR stat () +and +.BR lstat () +for a relative pathname). +.PP +If +.I pathname +is relative and +.I dirfd +is the special value +.BR AT_FDCWD , +then +.I pathname +is interpreted relative to the current working +directory of the calling process (like +.BR stat () +and +.BR lstat ()). +.PP +If +.I pathname +is absolute, then +.I dirfd +is ignored. +.PP +.I flags +can either be 0, or include one or more of the following flags ORed: +.TP +.BR AT_EMPTY_PATH " (since Linux 2.6.39)" +.\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d +If +.I pathname +is an empty string, operate on the file referred to by +.I dirfd +(which may have been obtained using the +.BR open (2) +.B O_PATH +flag). +In this case, +.I dirfd +can refer to any type of file, not just a directory, and +the behavior of +.BR fstatat () +is similar to that of +.BR fstat (). +If +.I dirfd +is +.BR AT_FDCWD , +the call operates on the current working directory. +This flag is Linux-specific; define +.B _GNU_SOURCE +.\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed +to obtain its definition. +.TP +.BR AT_NO_AUTOMOUNT " (since Linux 2.6.38)" +Don't automount the terminal ("basename") component of +.I pathname. +Since Linux 3.1 this flag is ignored. +Since Linux 4.11 this flag is implied. +.TP +.B AT_SYMLINK_NOFOLLOW +If +.I pathname +is a symbolic link, do not dereference it: +instead return information about the link itself, like +.BR lstat (). +(By default, +.BR fstatat () +dereferences symbolic links, like +.BR stat ().) +.PP +See +.BR openat (2) +for an explanation of the need for +.BR fstatat (). +.SH RETURN VALUE +On success, zero is returned. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EACCES +Search permission is denied for one of the directories +in the path prefix of +.IR pathname . +(See also +.BR path_resolution (7).) +.TP +.B EBADF +.I fd +is not a valid open file descriptor. +.TP +.B EBADF +.RB ( fstatat ()) +.I pathname +is relative but +.I dirfd +is neither +.B AT_FDCWD +nor a valid file descriptor. +.TP +.B EFAULT +Bad address. +.TP +.B EINVAL +.RB ( fstatat ()) +Invalid flag specified in +.IR flags . +.TP +.B ELOOP +Too many symbolic links encountered while traversing the path. +.TP +.B ENAMETOOLONG +.I pathname +is too long. +.TP +.B ENOENT +A component of +.I pathname +does not exist or is a dangling symbolic link. +.TP +.B ENOENT +.I pathname +is an empty string and +.B AT_EMPTY_PATH +was not specified in +.IR flags . +.TP +.B ENOMEM +Out of memory (i.e., kernel memory). +.TP +.B ENOTDIR +A component of the path prefix of +.I pathname +is not a directory. +.TP +.B ENOTDIR +.RB ( fstatat ()) +.I pathname +is relative and +.I dirfd +is a file descriptor referring to a file other than a directory. +.TP +.B EOVERFLOW +.I pathname +or +.I fd +refers to a file whose size, inode number, +or number of blocks cannot be represented in, respectively, the types +.IR off_t , +.IR ino_t , +or +.IR blkcnt_t . +This error can occur when, for example, +an application compiled on a 32-bit platform without +.I \-D_FILE_OFFSET_BITS=64 +calls +.BR stat () +on a file whose size exceeds +.I (1<<31)\-1 +bytes. +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +.TP +.BR stat () +.TQ +.BR fstat () +.TQ +.BR lstat () +SVr4, 4.3BSD, POSIX.1-2001. +.\" SVr4 documents additional +.\" .BR fstat () +.\" error conditions EINTR, ENOLINK, and EOVERFLOW. SVr4 +.\" documents additional +.\" .BR stat () +.\" and +.\" .BR lstat () +.\" error conditions EINTR, EMULTIHOP, ENOLINK, and EOVERFLOW. +.TP +.BR fstatat () +POSIX.1-2008. +Linux 2.6.16, +glibc 2.4. +.PP +According to POSIX.1-2001, +.BR lstat () +on a symbolic link need return valid information only in the +.I st_size +field and the file type of the +.I st_mode +field of the +.I stat +structure. +POSIX.1-2008 tightens the specification, requiring +.BR lstat () +to return valid information in all fields except the mode bits in +.IR st_mode . +.PP +Use of the +.I st_blocks +and +.I st_blksize +fields may be less portable. +(They were introduced in BSD. +The interpretation differs between systems, +and possibly on a single system when NFS mounts are involved.) +.SS C library/kernel differences +Over time, increases in the size of the +.I stat +structure have led to three successive versions of +.BR stat (): +.IR sys_stat () +(slot +.IR __NR_oldstat ), +.IR sys_newstat () +(slot +.IR __NR_stat ), +and +.I sys_stat64() +(slot +.IR __NR_stat64 ) +on 32-bit platforms such as i386. +The first two versions were already present in Linux 1.0 +(albeit with different names); +.\" See include/asm-i386/stat.h in the Linux 2.4 source code for the +.\" various versions of the structure definitions +the last was added in Linux 2.4. +Similar remarks apply for +.BR fstat () +and +.BR lstat (). +.PP +The kernel-internal versions of the +.I stat +structure dealt with by the different versions are, respectively: +.TP +.I __old_kernel_stat +The original structure, with rather narrow fields, and no padding. +.TP +.I stat +Larger +.I st_ino +field and padding added to various parts of the structure to +allow for future expansion. +.TP +.I stat64 +Even larger +.I st_ino +field, +larger +.I st_uid +and +.I st_gid +fields to accommodate the Linux-2.4 expansion of UIDs and GIDs to 32 bits, +and various other enlarged fields and further padding in the structure. +(Various padding bytes were eventually consumed in Linux 2.6, +with the advent of 32-bit device IDs and nanosecond components +for the timestamp fields.) +.PP +The glibc +.BR stat () +wrapper function hides these details from applications, +invoking the most recent version of the system call provided by the kernel, +and repacking the returned information if required for old binaries. +.\" +.\" A note from Andries Brouwer, July 2007 +.\" +.\" > Is the story not rather more complicated for some calls like +.\" > stat(2)? +.\" +.\" Yes and no, mostly no. See /usr/include/sys/stat.h . +.\" +.\" The idea is here not so much that syscalls change, but that +.\" the definitions of struct stat and of the types dev_t and mode_t change. +.\" This means that libc (even if it does not call the kernel +.\" but only calls some internal function) must know what the +.\" format of dev_t or of struct stat is. +.\" The communication between the application and libc goes via +.\" the include file <sys/stat.h> that defines a _STAT_VER and +.\" _MKNOD_VER describing the layout of the data that user space +.\" uses. Each (almost each) occurrence of stat() is replaced by +.\" an occurrence of xstat() where the first parameter of xstat() +.\" is this version number _STAT_VER. +.\" +.\" Now, also the definitions used by the kernel change. +.\" But glibc copes with this in the standard way, and the +.\" struct stat as returned by the kernel is repacked into +.\" the struct stat as expected by the application. +.\" Thus, _STAT_VER and this setup cater for the application-libc +.\" interface, rather than the libc-kernel interface. +.\" +.\" (Note that the details depend on gcc being used as c compiler.) +.PP +On modern 64-bit systems, life is simpler: there is a single +.BR stat () +system call and the kernel deals with a +.I stat +structure that contains fields of a sufficient size. +.PP +The underlying system call employed by the glibc +.BR fstatat () +wrapper function is actually called +.BR fstatat64 () +or, on some architectures, +.\" strace(1) shows the name "newfstatat" on x86-64 +.BR newfstatat (). +.SH EXAMPLES +The following program calls +.BR lstat () +and displays selected fields in the returned +.I stat +structure. +.PP +.\" SRC BEGIN (stat.c) +.EX +#include <stdint.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/stat.h> +#include <sys/sysmacros.h> +#include <time.h> +\& +int +main(int argc, char *argv[]) +{ + struct stat sb; +\& + if (argc != 2) { + fprintf(stderr, "Usage: %s <pathname>\en", argv[0]); + exit(EXIT_FAILURE); + } +\& + if (lstat(argv[1], &sb) == \-1) { + perror("lstat"); + exit(EXIT_FAILURE); + } +\& + printf("ID of containing device: [%x,%x]\en", + major(sb.st_dev), + minor(sb.st_dev)); +\& + printf("File type: "); +\& + switch (sb.st_mode & S_IFMT) { + case S_IFBLK: printf("block device\en"); break; + case S_IFCHR: printf("character device\en"); break; + case S_IFDIR: printf("directory\en"); break; + case S_IFIFO: printf("FIFO/pipe\en"); break; + case S_IFLNK: printf("symlink\en"); break; + case S_IFREG: printf("regular file\en"); break; + case S_IFSOCK: printf("socket\en"); break; + default: printf("unknown?\en"); break; + } +\& + printf("I\-node number: %ju\en", (uintmax_t) sb.st_ino); +\& + printf("Mode: %jo (octal)\en", + (uintmax_t) sb.st_mode); +\& + printf("Link count: %ju\en", (uintmax_t) sb.st_nlink); + printf("Ownership: UID=%ju GID=%ju\en", + (uintmax_t) sb.st_uid, (uintmax_t) sb.st_gid); +\& + printf("Preferred I/O block size: %jd bytes\en", + (intmax_t) sb.st_blksize); + printf("File size: %jd bytes\en", + (intmax_t) sb.st_size); + printf("Blocks allocated: %jd\en", + (intmax_t) sb.st_blocks); +\& + printf("Last status change: %s", ctime(&sb.st_ctime)); + printf("Last file access: %s", ctime(&sb.st_atime)); + printf("Last file modification: %s", ctime(&sb.st_mtime)); +\& + exit(EXIT_SUCCESS); +} +.EE +.\" SRC END +.SH SEE ALSO +.BR ls (1), +.BR stat (1), +.BR access (2), +.BR chmod (2), +.BR chown (2), +.BR readlink (2), +.BR statx (2), +.BR utime (2), +.BR stat (3type), +.BR capabilities (7), +.BR inode (7), +.BR symlink (7) |