.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH KEYCTL_UPDATE 2const (date) "Linux man-pages (unreleased)"
.SH NAME
KEYCTL_UPDATE
\-
update a key's data payload
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/keyctl.h>" "  /* Definition of " KEY* " constants */"
.BR "#include <sys/syscall.h>" "   /* Definition of " SYS_* " constants */"
.B #include <unistd.h>
.P
.BR "long syscall(" "size_t size;"
.BI "             SYS_keyctl, KEYCTL_UPDATE, key_serial_t " key ,
.BI "             void " payload [ size "], size_t " size );
.fi
.SH DESCRIPTION
Update a key's data payload.
.P
.I key
specifies the ID of the key to be updated.
.I payload
points to the new payload and
.I size
contains the new payload size in bytes.
.P
The caller must have
.I write
permission on the key specified and the key type must support updating.
.P
A negatively instantiated key
(see
.BR KEYCTL_REJECT (2const))
can be positively instantiated with this operation.
.SH RETURN VALUE
On success,
0 is returned.
.P
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
The key type does not support updating.
.SH VERSIONS
A wrapper is provided in the
.I libkeyutils
library:
.BR keyctl_update (3).
.SH STANDARDS
Linux.
.SH HISTORY
Linux 2.6.10.
.SH SEE ALSO
.BR keyctl (2),
.BR keyctl_update (3)