Return to intro.4 CVS log

Up to [Research Unix] / researchv10dc / man / man4

Annotation of researchv10dc/man/man4/intro.4, revision 1.1.1.1

1.1       root        1: .TH INTRO 4
                      2: .SH NAME
                      3: intro \- introduction to devices, line disciplines, and file systems
                      4: .SH DESCRIPTION
                      5: This section describes drivers for
                      6: devices,
                      7: stream line disciplines,
                      8: and file systems.
                      9: .PP
                     10: Devices are accessed through
                     11: special files of type
                     12: .L S_IFBLK
                     13: (block devices)
                     14: or
                     15: .L S_IFCHR
                     16: (character devices);
                     17: see
                     18: .IR stat (2).
                     19: Block devices use a block buffering scheme
                     20: within the system,
                     21: so that sectored devices like disks
                     22: may be accessed a byte at a time.
                     23: Character devices don't use the block buffers.
                     24: Only block devices may be mounted as disk file systems.
                     25: Most block devices
                     26: have associated `raw' character devices
                     27: that bypass all buffering for fast direct I/O.
                     28: .PP
                     29: The device associated with a special file is
                     30: identified by a pair of numbers:
                     31: a major device number
                     32: naming the driver,
                     33: and a minor device number
                     34: picking some particular device or subunit.
                     35: Major numbers are listed in
                     36: .IR mknod (8).
                     37: Minor numbers are specific to each driver;
                     38: see the writeups in this section.
                     39: Minor numbers are stored in a single unsigned byte;
                     40: they are chosen from the range 0-255.
                     41: .PP
                     42: Some character devices are also
                     43: stream devices.
                     44: These use a different internal buffering mechanism
                     45: to allow data to flow asynchronously.
                     46: Various special operations are possible on streams;
                     47: see
                     48: .IR stream (4).
                     49: .PP
                     50: Line disciplines are
                     51: processing modules that may be inserted into streams.
                     52: They are identified by integers
                     53: passed to the calls that insert and remove them.
                     54: The C library
                     55: contains global variables
                     56: initialized to the numbers
                     57: for various line disciplines;
                     58: .IR stream (4)
                     59: has a list.
                     60: .PP
                     61: There are several different types of file system:
                     62: conventional disk volumes,
                     63: remote file systems
                     64: accessed
                     65: by the system sending messages though a stream
                     66: to a server as described in
                     67: .IR netfs (8),
                     68: a file system containing a file representing
                     69: each process in the system,
                     70: and so on.
                     71: All of these
                     72: appear the same to ordinary processes,
                     73: except that not all file systems
                     74: implement all operations;
                     75: for example,
                     76: a process file has a name,
                     77: and may be opened, read, and written
                     78: like an ordinary file,
                     79: but may not be renamed because
                     80: .IR proc (4)
                     81: doesn't allow that.
                     82: .PP
                     83: File system types are
                     84: identified by integers,
                     85: used by and listed in
                     86: .IR fmount (2).
                     87: They are just magic numbers at present.
                     88: .SH SEE ALSO
                     89: .IR fmount (2),
                     90: .IR stream (4),
                     91: .IR mknod (8)

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.