NAME
ftok – generate an IPC key
SYNOPSIS
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#include <sys/ipc.h> key_t ftok(const char *path, int id); |
DESCRIPTION
The ftok() function shall return a key based on path and id that is usable in subsequent calls to msgget(), semget(), and shmget(). The application shall ensure that the path argument is the pathname of an existing file that the process is able to stat().
The ftok() function shall return the same key value for all paths that name the same file, when called with the same id value, and return different key values when called with different id values or with paths that name different files existing on the same file system at the same time. It is unspecified whether ftok() shall return the same key value when called again after the file named by path is removed and recreated with the same name.
Only the low-order 8-bits of id are significant. The behavior of ftok() is unspecified if these bits are 0.
RETURN VALUE
Upon successful completion, ftok() shall return a key. Otherwise, ftok() shall return (key_t)-1 and set errno to indicate the error.
ERRORS
The ftok() function shall fail if:
[EACCES]
Search permission is denied for a component of the path prefix.
[ELOOP]
A loop exists in symbolic links encountered during resolution of the path argument
[ENAMETOOLONG]
The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_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.
The ftok() function may fail if:
[ELOOP]
More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.
[ENAMETOOLONG]
Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.