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[thirdparty/man-pages.git] / man2 / readlinkat.2

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.TH READLINKAT 2 2012-05-04 "Linux" "Linux Programmer's Manual"
.SH NAME
readlinkat \- read value of a symbolic link relative to
a directory file descriptor
.SH SYNOPSIS
.nf
.B #include <fcntl.h>           /* Definition of AT_* constants */
.B #include <unistd.h>
.sp
.BI "int readlinkat(int " dirfd ", const char *" pathname ,
.BI "               char *" buf ", size_t " bufsiz );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR readlinkat ():
.PD 0
.ad l
.RS 4
.TP 4
Since glibc 2.10:
_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_ATFILE_SOURCE
.RE
.ad
.PD
.SH DESCRIPTION
The
.BR readlinkat ()
system call operates in exactly the same way as
.BR readlink (2),
except for the differences described in this manual page.

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 readlink (2)
for a relative pathname).

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 readlink (2)).

If
.I pathname
is absolute, then
.I dirfd
is ignored.
.SH RETURN VALUE
On success,
.BR readlinkat ()
returns the number of bytes placed in
.IR buf .
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
The same errors that occur for
.BR readlink (2)
can also occur for
.BR readlinkat ().
The following additional errors can occur for
.BR readlinkat ():
.TP
.B EBADF
.I dirfd
is not a valid file descriptor.
.TP
.B ENOTDIR
.I pathname
is relative and
.I dirfd
is a file descriptor referring to a file other than a directory.
.SH VERSIONS
.BR readlinkat ()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
.SH CONFORMING TO
POSIX.1-2008.
.SH NOTES
See
.BR openat (2)
for an explanation of the need for
.BR readlinkat ().
.SH SEE ALSO
.BR openat (2),
.BR readlink (2),
.BR path_resolution (7)