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ftok(3)
NAME
  ftok - Generate a standard interprocess communication key

SYNOPSIS
  #include <sys/ipc.h>

  key_t ftok(
	  const char *path_name,
	  int project_id );

  The following definition of the ftok() function does not conform to current
  standards and is supported only for backward compatibility:

  #include <sys/types.h>
  #include <sys/ipc.h>

  key_t ftok(
	  char *path_name,
	  char project_id );

LIBRARY
  Standard C Library (libc)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  ftok():  XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  path_name
      Specifies the pathname of an existing file that is accessible to the
      process.

  project_id
      Specifies a value that uniquely identifies a project.

DESCRIPTION
  The ftok() function returns a key, based on the path_name and project_id
  parameters, that is usable in subsequent calls to the msgget(), semget(),
  and shmget() functions. The ftok() function returns the same key for all
  paths that name the same file, when called with the same project_id
  parameter.  Different keys are returned for the same file if different
  project_id parameters are used, or if paths are used that name different
  files existing on the same file system at the same time. If a file named by
  path_name is removed and recreated with the same name, the ftok() function
  may return a different key than the original one.

  Only the low order 8-bits of project_id are significant.  The behavior of
  ftok() is unspecified if these bits are 0.

  For maximum portability, project_id should be a single-byte character.

RETURN VALUES
  Upon successful completion, the ftok() function returns a key. Otherwise,
  ftok() returns the value (key_t)-1 and sets errno to indicate the error.

ERRORS
  The ftok() function sets errno to the specified values for the following
  conditions:

  [EACCES]
      Search permission is denied for a component of the path_name parameter.

  [ELOOP]
      Too many symbolic links were encountered in resolving path_name.

  [ENAMETOOLONG]
      The length of the path_name parameter exceeds PATH_MAX, or a pathname
      component is longer than NAME_MAX. Or, pathname resolution of a
      symbolic link produced an intermediate result whose length exceeds
      PATH_MAX.

  [ENOENT]
      The path_name parameter points to the name of a file that does not
      exist or points to an empty string.

  [ENOTDIR]
      A component of the path_name parameter is not a directory.

SEE ALSO
  Functions: msgget(2), semget(2), shmget(2)

  Standards: standards(5)

Index for Section 3

Alphabetical listing for F

Top of page