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ftok(3) [netbsd man page]

FTOK(3) 						   BSD Library Functions Manual 						   FTOK(3)

NAME
ftok -- create IPC identifier from path name LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/types.h> #include <sys/ipc.h> key_t ftok(const char *path, int id); DESCRIPTION
The ftok() function attempts to create a unique key suitable for use with the msgget(2), semget(2) and shmget(2) functions given the path of an existing file and a user-selectable id. The specified path must specify an existing file that is accessible to the calling process or the call will fail. Also, note that links to files will return the same key, given the same id. Only the 8 least significant bits of id are used in the key generation; the rest of the bits are ignored. RETURN VALUES
The ftok() function will return ((key_t)-1) if path does not exist or if it cannot be accessed by the calling process. SEE ALSO
msgget(2), semget(2), shmget(2) STANDARDS
The ftok() function conforms to IEEE Std 1003.1 (``POSIX.1''). HISTORY
The ftok() function originated with System V and is typically used by programs that use the System V IPC routines. AUTHORS
Thorsten Lockert <tholo@sigmasoft.com> BUGS
The returned key is computed based on the device and inode of the specified path in combination with the given id. Thus it is quite possible for the routine to return duplicate keys given that those fields are not 8- and 16-bit quantities like they were on System V based systems where this library routine's ancestor were originally created. BSD
April 27, 2010 BSD

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FTOK(3) 						   BSD Library Functions Manual 						   FTOK(3)

NAME
ftok -- create IPC identifier from path name LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/ipc.h> key_t ftok(const char *path, int id); DESCRIPTION
The ftok() function attempts to create a unique key suitable for use with the semget(2), and shmget(2) functions, given the path of an exist- ing file and a user-selectable id. The specified path must specify an existing file that is accessible to the calling process or the call will fail. Also, note that links to files will return the same key, given the same id. RETURN VALUES
The ftok() function will return -1 if path does not exist or if it cannot be accessed by the calling process. LEGACY SYNOPSIS
#include <sys/types.h> #include <sys/ipc.h> The include file <sys/types.h> is necessary. SEE ALSO
semget(2), shmget(2), compat(5) HISTORY
The ftok() function originates with System V and is typically used by programs that use the System V IPC routines. AUTHORS
Thorsten Lockert <tholo@sigmasoft.com> BUGS
The returned key is computed based on the device minor number and inode of the specified path, in combination with the lower 8 bits of the given id. Thus, it is quite possible for the routine to return duplicate keys. BSD
July 9, 2009 BSD

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