|lookup_dcookie(2)||System Calls Manual||lookup_dcookie(2)|
lookup_dcookie - return a directory entry's path
Standard C library (libc, -lc)
#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).
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.
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.
- The buffer was not valid.
- 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.
- The name could not fit in the buffer.
- The kernel could not allocate memory for the temporary buffer holding the path.
- The process does not have the capability CAP_SYS_ADMIN required to look up cookie values.
- The buffer was not large enough to hold the path of the directory entry.
The ENAMETOOLONG error was added in Linux 2.5.70.
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.
|2023-03-30||Linux man-pages 6.04|