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LOOKUP_DCOOKIE

Section: Linux Programmer's Manual (2)
Updated: 2017-09-15
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NAME

lookup_dcookie - return a directory entry's path

SYNOPSIS

int lookup_dcookie(u64 cookie, char *buffer, size_t len);

DESCRIPTION

Look up the full path of the directory entry specified by the value cookie. The cookie is an opaque identifier uniquely identifying a particular 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 appropriately.

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 directory 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 directory entry.

VERSIONS

Available since Linux 2.5.43. The ENAMETOOLONG error return was added in 2.5.70.

CONFORMING TO

lookup_dcookie() is Linux-specific.

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 directory entry has been removed.

COLOPHON

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