HP 3000 Manuals HP 3000 Manuals
New File Types Release 4.5 and 5.0 of MPE/iX provide some new file types. Here is a brief definition of them. Since these interfaces are based on a commonly used standard, many textbooks are available that contain a detailed discussion of their use. Byte-Stream Files Byte stream files are simply a sequence (stream) of bytes. The term byte stream file is frequently used when talking about files with the byte stream record type, even though they are not a new file type. Byte stream files do not have any record structure associated with them and have a record size of 1 byte. Also, they allow reading and writing of data in arbitrary sized chunks. Symbolic Links on MPE/iX A symbolic link is a type of file that contains another pathname. It is a permanent file in the system directory. This concept is similar to MPE/iX file equations. A symbolic link file may contain a relative or absolute path name. If a symbolic link to a relative path name is encountered during path name traversal, the contents of the symbolic link replaces the symbolic link component and is expanded into the path name being interpreted. If a symbolic link to an absolute path name is encountered, the contents of the symbolic link replaces all components up to and including the symbolic link and is expanded into the remainder of the path name. For example, if the path name /dir1/dir2/syml/file is being traversed and the component syml is a symbolic link that points to the relative path dir3/dir4, then the final path name resolved is: /dir1/dir2/dir3/dir4/file. However, if syml contains the absolute path /dir4/dir5, then the final pathname resolved is: /dir4/dir5/file. All symbolic links are interpreted in this manner except when the symbolic link is the last component of a pathname passed as a parameter to one of the following POSIX functions: READLINK, RENAME, SYMLINK, UNLINK, CHOWN, and LSTAT. With these calls, the symbolic link itself is accessed or affected. Pipes A pipe consists of two file descriptors connected such that data written to one can be read from the other in a first-in-first-out manner. FIFOs A FIFO is a named pipe. Because a FIFO has a directory name, it can be used by non-related processes to perform interprocess communication.