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openat(2) [linux man page]

OPENAT(2)						     Linux Programmer's Manual							 OPENAT(2)

NAME
openat - open a file relative to a directory file descriptor SYNOPSIS
#include <fcntl.h> int openat(int dirfd, const char *pathname, int flags); int openat(int dirfd, const char *pathname, int flags, mode_t mode); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): openat(): Since glibc 2.10: _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCE DESCRIPTION
The openat() system call operates in exactly the same way as open(2), except for the differences described in this manual page. If the pathname given in pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by open(2) for a relative pathname). If pathname is relative and dirfd is the special value AT_FDCWD, then pathname is interpreted relative to the current working directory of the calling process (like open(2)). If pathname is absolute, then dirfd is ignored. RETURN VALUE
On success, openat() returns a new file descriptor. On error, -1 is returned and errno is set to indicate the error. ERRORS
The same errors that occur for open(2) can also occur for openat(). The following additional errors can occur for openat(): EBADF dirfd is not a valid file descriptor. ENOTDIR pathname is relative and dirfd is a file descriptor referring to a file other than a directory. VERSIONS
openat() was added to Linux in kernel 2.6.16. CONFORMING TO
POSIX.1-2008. A similar system call exists on Solaris. NOTES
openat() and other similar system calls suffixed "at" are supported for two reasons. First, openat() allows an application to avoid race conditions that could occur when using open(2) to open files in directories other than the current working directory. These race conditions result from the fact that some component of the directory prefix given to open(2) could be changed in parallel with the call to open(2). Such races can be avoided by opening a file descriptor for the target directory, and then specifying that file descriptor as the dirfd argument of openat(). Second, openat() allows the implementation of a per-thread "current working directory", via file descriptor(s) maintained by the applica- tion. (This functionality can also be obtained by tricks based on the use of /proc/self/fd/dirfd, but less efficiently.) SEE ALSO
faccessat(2), fchmodat(2), fchownat(2), fstatat(2), futimesat(2), linkat(2), mkdirat(2), mknodat(2), open(2), readlinkat(2), renameat(2), symlinkat(2), unlinkat(2), utimensat(2), mkfifoat(3), path_resolution(7) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2009-12-13 OPENAT(2)

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MKFIFOAT(3)						     Linux Programmer's Manual						       MKFIFOAT(3)

NAME
mkfifoat - make a FIFO (named pipe) relative to a directory file descriptor SYNOPSIS
#include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int mkfifoat(int dirfd, const char *pathname, mode_t mode); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mkfifoat(): Since glibc 2.10: _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCE DESCRIPTION
The mkfifoat() system call operates in exactly the same way as mkfifo(3), except for the differences described in this manual page. If the pathname given in pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by mkfifo(3) for a relative pathname). If pathname is relative and dirfd is the special value AT_FDCWD, then pathname is interpreted relative to the current working directory of the calling process (like mkfifo(3)). If pathname is absolute, then dirfd is ignored. RETURN VALUE
On success, mkfifoat() returns 0. On error, -1 is returned and errno is set to indicate the error. ERRORS
The same errors that occur for mkfifo(3) can also occur for mkfifoat(). The following additional errors can occur for mkfifoat(): EBADF dirfd is not a valid file descriptor. ENOTDIR pathname is a relative path and dirfd is a file descriptor referring to a file other than a directory. VERSIONS
mkfifoat() was added to glibc in version 2.4. It is implemented using mknod(2), available on Linux since kernel 2.6.16. CONFORMING TO
POSIX.1-2008. NOTES
See openat(2) for an explanation of the need for mkfifoat(). SEE ALSO
openat(2), mkfifo(3), path_resolution(7) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2009-12-13 MKFIFOAT(3)

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