Standards
| Standards / Extensions |
C or C++ |
Dependencies |
|---|
XPG4.2
Single UNIX Specification, Version 3
|
both |
|
Format
#define _XOPEN_SOURCE_EXTENDED 1
#include <sys/ipc.h>
key_t ftok(const char *path, int id);
General description
The ftok()
function returns a key based on path and id that
is usable in subsequent calls to msgget(), semget(), and shmget().
The path argument must be the path name
of an existing file that the process is able to stat().
The
ftok() function returns the same key value for all paths that name
the same file, when called with the same id value.
If a different id value is given, or a different
file is given, a different key is returned. Only the low-order 8-bits
of id are significant, and must be nonzero.
Returned value
If successful, ftok() returns
a key.
If unsuccessful, ftok() returns -1 and sets errno to
one of the following values:
- Error Code
- Description
- EACCES
- Search permission is denied for a component of the path prefix.
- EINVAL
- The low-order 8-bits of id are zero.
- ELOOP
- Too many symbolic links were encountered in resolving path.
- ENAMETOOLONG
- One of the following error conditions exists:
- The length of the path argument exceeds PATH_MAX or
a path name component is longer than NAME_MAX.
- The path name resolution of a symbolic link produced an intermediate
result whose length exceeds PATH_MAX.
- ENOENT
- A component of path does not name an
existing file or path is an empty string.
- ENOTDIR
- A component of the path prefix is not a directory.