lookup_dcookie(2) System Calls Manual lookup_dcookie(2)
NAME
lookup_dcookie - return a directory entry's path
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_lookup_dcookie, uint64_t cookie, char *buffer,
size_t len);
Note: glibc provides no wrapper for lookup_dcookie(), necessitating the
use of syscall(2).
DESCRIPTION
Look up the full path of the directory entry specified by the value
cookie. The cookie is an opaque identifier uniquely identifying a par-
ticular directory entry. The buffer given is filled in with the full
path of the directory entry.
For lookup_dcookie() to return successfully, the kernel must still hold
a cookie reference to the directory entry.
RETURN VALUE
On success, lookup_dcookie() returns the length of the path string
copied into the buffer. On error, -1 is returned, and errno is set to
indicate the error.
ERRORS
EFAULT The buffer was not valid.
EINVAL The kernel has no registered cookie/directory entry mappings at
the time of lookup, or the cookie does not refer to a valid di-
rectory entry.
ENAMETOOLONG
The name could not fit in the buffer.
ENOMEM The kernel could not allocate memory for the temporary buffer
holding the path.
EPERM The process does not have the capability CAP_SYS_ADMIN required
to look up cookie values.
ERANGE The buffer was not large enough to hold the path of the direc-
tory entry.
STANDARDS
Linux.
HISTORY
Linux 2.5.43.
The ENAMETOOLONG error was added in Linux 2.5.70.
NOTES
lookup_dcookie() is a special-purpose system call, currently used only
by the oprofile(1) profiler. It relies on a kernel driver to register
cookies for directory entries.
The path returned may be suffixed by the string " (deleted)" if the di-
rectory entry has been removed.
SEE ALSO
oprofile(1)
Linux man-pages 6.7 2023-10-31 lookup_dcookie(2)
Generated by dwww version 1.16 on Tue Jul 14 01:21:34 CEST 2026.