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1.1 root 1: .de H
2: .LP
3: .in 1n
4: .ti 0
5: .HI \\$1 \\$2 \\$3 \\$4 \\$5 \\$6
6: ..
7: .de HI
8: .B
9: \\$1 \\$2 \\$3 \\$4 \\$5 \\$6
10: .R
11: ..
12: .de C
13: .I
14: .if \\n(.$=1 \\$1
15: .if \\n(.$=2 \\$1 \\$2
16: .if \\n(.$=3 \\$1 \\$2 \\$3
17: .if \\n(.$=4 \\$1 \\$2 \\$3 \\$4
18: .if \\n(.$=5 \\$1 \\$2 \\$3 \\$4 \\$5
19: .if \\n(.$=6 \\$1 \\$2 \\$3 \\$4 \\$5 \\$6
20: .R
21: ..
22: .rs
23: .SP .5i
24: .TL
25: GLOSSARY
26: .SP 2
27: .LP
28: This glossary covers major terms that have special meaning for the
29: UNIX system.
30: It excludes ordinary terms of art such as
31: `ASCII', `compiler', `address space', or `byte'.
32: It also excludes most terms peculiar to a single part of UNIX, e.g.
33: `diversion' (\fItroff\fR), `enumeration' (C),
34: or `pattern space' (\fIsed\fR).
35: .SP 1.3v
36: .nr PS 9
37: .nr VS 10
38: .2C
39: .H absolute pathname\
40: same as
41: .C full pathname.
42: .nr PD 1u
43: .H access time\
44: the most recent
45: .C time
46: at which the contents of a
47: .C file
48: [2] were read or
49: .C executed
50: [2]; cf.\&
51: .C modification time.
52: .H alarm\
53: a
54: .C signal
55: scheduled by the clock.
56: .H a.out\
57: the default name of a freshly compiled
58: .C object file,
59: pronounced `A-dot-out';
60: historically
61: .CW a.out
62: signified assembler output.
63: .H archive\
64: 1.\&
65: a collection of data gathered from several
66: .C files
67: into one file.
68: 2.\&
69: especially, such a collection gathered by
70: .I ar (1)
71: for use as a
72: .C library.
73: .H argument\
74: 1.\&
75: a
76: string made available to a
77: .C process
78: upon
79: .C executing
80: a
81: .C file.
82: 2.\&
83: a string in a
84: .C command,
85: which the
86: .C shell
87: [1] will pass to the command program
88: as an argument [1].
89: .H ASCII file\
90: same as
91: .C text file.
92: .H automatic\
93: persistent only during the invocation of a procedure, said of
94: data belonging to a
95: .C process;
96: automatic data occupies the
97: .C stack segment;
98: cf.\&
99: .C static.
100: .H background\
101: running independently of a
102: terminal, said of a
103: .C process;
104: converse of
105: .C foreground.
106: .H basename\
107: 1.\&
108: the last component of a
109: .C pathname;
110: the basename of
111: .CW /bin/proc
112: is
113: .CW proc .
114: 2.\&
115: occasionally a basename [1] with conventional
116: suffixes removed; see
117: .I basename (1).
118: .H blit\
119: vernacular name for a prototype
120: Teletype 5620 terminal; cf.\&
121: .C jerq.
122: .H block\
123: 1. \&
124: the basic unit of
125: .C buffering
126: [1]
127: in a
128: .C file system
129: [3], 1024 or 4096 bytes in this system.
130: 2. \&
131: a unit in which memory usage is reported, usually 1024 bytes,
132: but 512 bytes in imported code such as
133: .I cpio (1).
134: .H block device\
135: a
136: .C device
137: that may contain a
138: .C file system
139: [3],
140: typically a permanent storage device such as a tape or
141: disk drive; the unit of data transfer is one
142: .C block;
143: cf.\&
144: .C character device.
145: .H boot\
146: to start the operating system, so called because the
147: .C kernel
148: must bootstrap itself from secondary store into an empty machine.
149: No
150: .C login
151: [3]
152: or
153: .C process
154: persists across a boot.
155: .H boot block\
156: the first block of a
157: .C file system
158: [1],
159: which is reserved for a
160: .C booting
161: program.
162: .H break\
163: 1.\&
164: an out-of-band signal on an asynchronous data line arising from
165: the `break' or `interrupt' key on a terminal;
166: before
167: .C logging in
168: a break causes a change in baud rate;
169: thereafter it is interpreted as an
170: .C interrupt.
171: 2.\&
172: a control statement in C or
173: .I sh (1).
174: 3.\&
175: the
176: .C program break.
177: 4.\&
178: in
179: .I troff (1),
180: a point in running text where a new line must begin.
181: .H BSD\
182: see
183: .C UNIX.
184: .H bss segment\
185: see
186: .C segment.
187: .H buffer\
188: 1.\&
189: a staging area for input-output where arbitrary-length
190: transactions are collected into convenient units for system operations.
191: 2.\&
192: to use buffers.
193: .H buffer pool\
194: a region of
195: .C kernel
196: memory available for holding
197: .C blocks;
198: non-\c
199: .C raw
200: input-output for
201: .C block devices
202: and
203: .C file systems
204: [3]
205: goes through the buffer pool to make
206: read and write operations
207: independent of device format.
208: .H cbreak\
209: a mode of terminal input in which every character not a
210: .C special character
211: becomes available to a
212: .I read (2)
213: operation as soon as it is typed, instead of being
214: .C buffered
215: up to a
216: .C newline
217: or
218: .C EOT character.
219: .H change time\
220: the most recent
221: .C time
222: at which the contents of a
223: .C file
224: [2] or its
225: .C inode
226: properties (e.g.
227: .C owner
228: and
229: .I mode )
230: were altered;
231: cf.\&
232: .C modification time.
233: .H character\
234: 1.\&
235: a unit of store, usually 8 bits;
236: a byte.
237: 2.\&
238: a token of the
239: ASCII
240: code, with octal value in the range 0 to 0177.
241: .H character device\
242: a
243: .C device,
244: such as a terminal or the
245: .C null device,
246: that cannot contain a
247: .C file system
248: [3];
249: cf.\&
250: .C block device.
251: .H child process\
252: see
253: .C fork.
254: .H client\
255: a
256: .C process
257: that uses a service by
258: .C opening
259: the interface to a
260: .C server.
261: .H close\
262: to make an
263: .C open file
264: unavailable for input or output; converse of
265: .C open.
266: .H command\
267: 1.\&
268: an instruction to the
269: .C shell
270: [1], usually to run a
271: .C program
272: [1] as a
273: .C child process.
274: 2.\&
275: by extension, any
276: .C executable file,
277: especially a
278: .C utility program.
279: .H command file\
280: same as
281: .C shell script.
282: .H connection line discipline\
283: a
284: .C line discipline
285: used on
286: .C mounted streams
287: whereby each
288: .C opening
289: of the stream provides a new
290: .C pipe
291: to the stream's
292: .C server;
293: see
294: .I connld (4).
295: .H connection service\
296: a collection of
297: .C mounted streams,
298: conventionally in
299: .C directory
300: .CW /cs ,
301: that encapsulate generic setup protocols to reach
302: .C servers;
303: see
304: .I ipc (3).
305: .H control character\
306: an
307: ASCII
308: character with octal code 0-037 or 0177, which does not
309: print but may otherwise affect the behavior of a terminal;
310: cf.\&
311: .C special character.
312: .H control stream, control terminal\
313: a
314: .C stream
315: [2] associated with a
316: .C process
317: from which the process may receive
318: .C interrupt,
319: .C quit,
320: and
321: .C hangup
322: signals; cf.\&
323: .C process group.
324: The control stream is conventionally
325: .CW /dev/tty ,
326: .C file descriptor
327: 3.\&
328: .H cooked\
329: not
330: .C raw
331: [1],
332: said of an input
333: .C stream
334: [2] in which
335: .C special characters
336: are active.
337: .H cookie\
338: a peculiar goody, token, saying, or remembrance returned by or
339: presented to a
340: .C program
341: [3], cf.\&
342: .C file descriptor,
343: .C process number.
344: .H core file\
345: a
346: .C core image
347: of a terminated
348: .C process
349: saved for debugging; a core file is created under the name
350: .CW core
351: in the
352: .C current directory
353: of the process.
354: .H core image\
355: the data of a running or terminated
356: .C process;
357: the data may reside physically in main store, in the
358: .C swap area,
359: or in a
360: .C core file,
361: and logically in a
362: .C process file.
363: .H create\
364: to
365: .C open
366: a file for writing, bringing it into existence as a
367: .C plain file
368: if necessary, and discarding any data it may have
369: contained previously; cf.\&
370: .C unlink.
371: .H current directory, working directory\
372: the directory from which
373: .C relative pathnames
374: begin; a current directory is associated with each
375: .C process.
376: .H daemon\
377: a
378: .C background
379: process, often perpetual, that performs a system-wide public function, e.g.
380: .I calendar (1)
381: and
382: .I cron (8);
383: the affected spelling is an ancient legacy; cf.\&
384: .C server.
385: .H Datakit\
386: AT&T trademark for
387: a data network based on virtual circuit switching.
388: .H data segment\
389: see
390: .C segment.
391: .H date\
392: same as
393: .C time.
394: .H device\
395: 1.\&
396: a
397: .C file
398: [2]
399: that is not a
400: .C plain file
401: or a
402: .C directory,
403: examples are tape drive, terminal, a span of
404: .C blocks
405: on a disk drive, or the
406: .C null device;
407: a
408: .C special file.
409: 2.\&
410: a physical input-output unit.
411: .H device number\
412: a system-dependent code used in
413: .C inodes
414: to distinguish
415: .C devices
416: [1].
417: A device number has two parts:
418: .HI major device
419: for the type of the device and
420: .HI minor device
421: for an individual device of a type.
422: .H directory\
423: a
424: .C file
425: [2] that comprises a catalog of
426: .C filenames
427: [2];
428: the organizing principle of the
429: .C file system
430: [2],
431: a directory
432: consists of
433: .C entries
434: which specify further
435: files [2], including directories,
436: and constitutes a node of the
437: .C directory tree.
438: .H directory entry, entry\
439: 1.\&
440: an association of a name with an
441: .C inode number
442: appearing as an element of a
443: .C directory.
444: 2.\&
445: the name part of such an association.
446: .H directory hierarchy, directory tree, file hierarchy\
447: the tree of all
448: .C directories,
449: in which each is reachable from the
450: .C root
451: [2]
452: via a
453: .C path
454: of
455: .C subdirectories.
456: .H driver\
457: a set of
458: .C kernel
459: subroutines that handle input/output for a given
460: .C major device
461: type.
462: .H echo\
463: to transmit characters received from a terminal back to it;
464: the technique of echoing to a
465: .C full duplex
466: terminal provides acknowledgement of typed input.
467: .H effective userid\
468: see
469: .C set userid.
470: .H end of file\
471: the condition of the
472: .C read pointer
473: being past the last character of an
474: .C open file.
475: End of file is signified by a read operation
476: returning zero bytes, or by an EOF return
477: from functions of the
478: .C stdio
479: package; it may be simulated from a terminal by
480: typing EOT (control-D) after a
481: .C newline.
482: .H entry\
483: see
484: .C directory entry.
485: .H environment\
486: 1.\&
487: a set of strings, distinct from the
488: .C arguments,
489: made available to a
490: .C process
491: when it
492: .C executes
493: [1] a
494: .C file;
495: the environment is usually inherited across
496: .I exec (2)
497: operations.
498: 2.\&
499: a specific environment [1] maintained by the
500: .C shell
501: [1].
502: 3.\&
503: a nebulously identified way of doing things, as in
504: `interactive environment': deprecated usage, not always expunged
505: from these manuals.
506: .H EOF\
507: 1.\&
508: same as
509: .C end of file.
510: 2.\&
511: a conventional value returned at end of file by
512: .C stdio
513: functions.
514: .H EOT, EOT character\
515: 1.\&
516: the
517: ASCII
518: `end of transmission' character, control-D, octal code 04.
519: 2.\&
520: a character that ends (and is excluded from) data
521: obtained by
522: .I read (2)
523: from a terminal; EOT at the beginning of a line causes the
524: .C end of file
525: condition.
526: .H epoch\
527: see
528: .C time.
529: .H erase character\
530: a
531: .C special character
532: [2] which, when received from a terminal, is deleted
533: together with the character immediately preceding it on the line;
534: usually defaulted to
535: .CW #
536: or backspace, the erase character may be changed by
537: .I stty (1);
538: cf.\&
539: .C kill character.
540: .H escape character\
541: 1.\&
542: The ASCII character ESC, octal 033.
543: 2.\&
544: a
545: .C special character
546: that may cause the following character
547: to have other than its usual meaning;
548: the default escape character in terminal input is
549: .CW \e .
550: .H executable file, object program\
551: 1.\&
552: an
553: .C object file
554: that is ready to be copied into the
555: address space
556: of a
557: .C process
558: to run as the code of that process.
559: 2.\&
560: a file that has
561: execute
562: .C permission,
563: either an
564: .C executable file
565: [1] or a
566: .C shell script.
567: .H execute, exec\
568: 1.\&
569: to replace the
570: .C text segment
571: and
572: .C data segments
573: of a
574: .C process
575: with a given
576: .C program
577: [1]; see
578: .I exec (2).
579: 2.\&
580: informally, to run a
581: .C program.
582: .H exit\
583: to terminate a
584: .C process;
585: exit is voluntary, in contrast to
586: .C kill.
587: .H exit status, return code\
588: an integer value denoting the outcome of a
589: .C process,
590: including an indication of the cause of termination.
591: .H export\
592: 1.\&
593: to include in the
594: .C environment
595: [1] of a
596: .C process
597: when it is
598: .C executed
599: [1],
600: said of a string.
601: .H external\
602: known beyond the scope of a single compilation,
603: said of names of data and functions in a program.
604: .H file\
605: 1.\&
606: in general, a potential source of input or destination for output.
607: 2.\&
608: most specifically, an
609: .C inode
610: and/or associated contents, i.e. a
611: .C plain file,
612: a
613: .C special file,
614: or a
615: .C directory.
616: 3.\&
617: a
618: .C directory entry
619: [1];
620: several directory entries may name the same file [2].
621: 4.\&
622: most loosely, a
623: .C plain file.
624: .H file descriptor\
625: a conventional integer quantity, or
626: .C cookie,
627: that designates an
628: .C open file;
629: cf.\&
630: .C stream
631: [1].
632: .H file descriptor file\
633: a
634: .C special file
635: that serves as a name for an
636: .C open file
637: [1]; see
638: .I fd (4).
639: .H file hierarchy\
640: same as
641: .C directory hierarchy.
642: .H filename\
643: 1.\&
644: a
645: .C pathname.
646: 2.\&
647: same as
648: .C basename.
649: .H file pointer\
650: the number of the next byte that would normally
651: be read or written in a
652: .C file
653: [2]; also called
654: .C read pointer,
655: .C write pointer,
656: or
657: .C seek pointer.
658: .H file system\
659: 1.\&
660: a detachable part of the
661: .C directory hierarchy.
662: 2.\&
663: the collection of all
664: .C files
665: [2] accessible to a computer,
666: organized into a
667: directory hierarchy.
668: 3.\&
669: in particular a
670: .C block device
671: in which
672: .C files
673: [2] are organized according to an
674: .C i-list
675: and accessed by
676: .C paths
677: through
678: .C directories.
679: .H file system switch\
680: a
681: .C kernel
682: table that directs the interpretation of
683: operations in
684: .C file systems
685: [1] and
686: .C special file systems.
687: .H file times\
688: .C access time,
689: .C change time,
690: and
691: .C modification time.
692: .H filter\
693: a
694: .C program
695: [1]
696: that reads from the
697: .C standard input
698: and writes on the
699: .C standard output,
700: so called because it can be used as a data-transformer in a
701: .C pipeline.
702: .H flag\
703: same as
704: .C option.
705: .H flush\
706: to empty a
707: .C buffer,
708: for example to throw away unwanted input-output upon
709: .C interrupt
710: or to release output from the clutches of
711: .C stdio.
712: .H foreground\
713: running under direct control of a terminal, said of a
714: .C process;
715: converse of
716: .C background.
717: .H fork\
718: 1.\&
719: to split one
720: .C process
721: into two, the
722: .HI parent process
723: and
724: .HI child process,
725: with separate, but initially identical,
726: .C text, data,
727: and
728: .C stack
729: .C segments.
730: 2.\&
731: informally, same as
732: .C spawn.
733: .H free list\
734: in a
735: .C file system
736: [1],
737: the list of
738: .C blocks
739: that are not occupied by data.
740: .H full duplex\
741: 1.\&
742: capable of carrying information simultaneously in both directions,
743: said of a communication channel.
744: 2.\&
745: transmitting what is typed while printing what is received,
746: said of a terminal, or of terminal communication;
747: cf.\&
748: .C half duplex
749: and
750: .C echo.
751: .H gid\
752: see
753: .C groupid.
754: .H global\
755: same as
756: .C external.
757: .H group\
758: 1.\&
759: a set of
760: .C permissions
761: alternative to
762: .C owner
763: permissions for access to a
764: .C file.
765: 2.\&
766: a set of
767: .C userids
768: that may assume the privileges of a group [1].
769: 3.\&
770: the
771: .C groupid
772: of a
773: .C file.
774: .H group file\
775: the file
776: .CW /etc/group ,
777: which tells which
778: .C groupids
779: are available to each
780: .C login name.
781: .H groupid, gid\
782: an integer value associated with
783: .C processes
784: and
785: .C files
786: [2] used in determining
787: .C permissions.
788: .H half duplex\
789: 1.\&
790: capable of carrying information in both directions, but not simultaneously,
791: said of a communication channel.
792: 2.\&
793: transmitting (usually typing what is transmitted) and receiving,
794: but not simultaneously, said of a terminal; cf.\&
795: .C full duplex.
796: .H hang\
797: 1.\&
798: to
799: .C execute
800: a
801: .C program
802: [1] so that it stops immediately, usually for debugging; cf.\&
803: .I hang (1).
804: 2.\&
805: to wait for something that won't happen; said of a process.
806: .H hangup\
807: a
808: .C signal
809: indicating that a user's terminal
810: has been disconnected.
811: .H hard link\
812: 1.\&
813: a
814: .C directory entry
815: [1] that does not designate a
816: .C symbolic link.
817: 2.\&
818: a
819: .C link
820: [2] that is not a
821: .C symbolic link.
822: .H header file\
823: same as
824: .C include file;
825: the name of a header file customarily ends with
826: .CW \&.h
827: (dot-h).
828: .H here file\
829: in a
830: .C shell script,
831: literally given input data for a
832: .C command;
833: here files are introduced by
834: .CW << .
835: .H hole\
836: a gap in a
837: .C plain file
838: caused by
839: .C seeking
840: while writing;
841: .I read (2)
842: takes data in holes to be zero;
843: a
844: .C block
845: in a hole occupies no space in its
846: .C file system
847: [1].
848: .H home directory\
849: 1.\&
850: the
851: .C current directory
852: established for each user upon
853: .C logging in.
854: 2.\&
855: the variable
856: .CW HOME
857: in the
858: .C environment
859: [2], used in particular as the default destination for the
860: .C shell
861: [1]
862: .CW cd
863: command.
864: .H host process\
865: a
866: .C process
867: working in collaboration with a
868: .C terminal process.
869: .H HZ\
870: alternating-current line frequency,
871: 60 in North America, 50 in most other places.
872: .H i-list\
873: the index to a
874: .C file system
875: [1]
876: listing all the
877: .C inodes
878: of the file system; cf.\&
879: .C inode number.
880: .H image\
881: same as
882: .C core image.
883: .H include file, header file\
884: a
885: .C file
886: [4],
887: usually containing shared data declarations,
888: that is to be copied into source programs as they are compiled.
889: .H inode\
890: an element of a
891: .C file system
892: [1];
893: an inode specifies all properties of a particular
894: .C file
895: [2] and locates the file's contents, if any.
896: .H inode number, i-number\
897: the position of an
898: .C inode
899: in the
900: .C i-list
901: of a
902: .C file system
903: [1].
904: .H Internet\
905: an informal association of data networks using
906: protocols developed mainly under the auspices of
907: DARPA.
908: .H interrupt\
909: 1.\&
910: a
911: .C signal
912: that normally terminates a
913: .C process,
914: caused by a
915: .C break
916: [1]
917: or an
918: .C interrupt character;
919: cf.\&
920: .C quit.
921: 2.\&
922: loosely, any
923: .C signal.
924: .H interrupt character\
925: a character (normally
926: ASCII
927: DEL) that, when typed on a
928: .C control terminal,
929: causes an
930: .C interrupt.
931: .H io control, ioctl\
932: 1.\&
933: a
934: .C system call
935: that changes the behavior of an
936: .C open file,
937: for example in interpreting
938: .C control characters.
939: 2.\&
940: a function performed by
941: .I ioctl (2).
942: .H jerq\
943: vernacular name for a Teletype 5620 terminal.
944: .H K\
945: 1024; 1024 bytes: a `4K file system' has 4096-byte
946: .C blocks.
947: .H kernel\
948: the UNIX system proper;
949: resident code that implements the
950: .C system calls.
951: .H kernel space, kernel address space\
952: data and code that are addressable only by the
953: .C kernel.
954: .H kill\
955: 1.\&
956: a particular
957: .C signal
958: guaranteed to terminate a
959: .C process.
960: 2.\&
961: by extension, to send any
962: .C signal
963: to a
964: .C process.
965: 3.\&
966: the
967: .C kill character.
968: .H kill character\
969: a
970: .C special character,
971: which, when received from a terminal, is deleted together with
972: all preceding characters on the line;
973: defaulted to
974: .CW @ ,
975: the kill character may be changed by
976: .I stty (1);
977: cf.\&
978: .C erase character.
979: .H layer\
980: a virtual terminal appearing on a screen and also capable
981: of running
982: .C terminal processes.
983: The
984: .C processes
985: associated with each layer constitute
986: a separate
987: .C process group.
988: .H library\
989: an
990: .C archive
991: [2] of
992: .C object files
993: from which the
994: .C link editor
995: may select functions and data as needed.
996: .H line\
997: in a
998: .C text file,
999: a sequence of bytes terminated by a
1000: .C newline.
1001: .H line discipline\
1002: a module to handle protocol or data
1003: conversion for a
1004: .C stream
1005: [2].
1006: A line discipline, unlike a
1007: .C filter,
1008: is part of the
1009: .C kernel.
1010: .H link\
1011: 1.\&
1012: to add
1013: an entry for an existing
1014: .C file
1015: [2] to a directory;
1016: converse of
1017: .C unlink.
1018: 2.\&
1019: particularly, any but one putatively primary directory entry for
1020: a given
1021: .C inode,
1022: either linked [1] or a
1023: .C symbolic link.
1024: .H link count\
1025: the number of
1026: .C directory entries
1027: [1] that pertain to an
1028: .C inode;
1029: a
1030: .C file
1031: [2] ceases to exist
1032: when its link count becomes zero
1033: and it is not
1034: .C open.
1035: .H link editor, loader\
1036: the utility
1037: .I ld (1),
1038: which combines separately compiled
1039: .C object files
1040: into a single
1041: object file.
1042: .H listen\
1043: to issue a read on a
1044: .C stream,
1045: waiting for data, usually a service request, from some other
1046: .C process
1047: or
1048: .C remote
1049: source.
1050: .H loader\
1051: same as
1052: .C link editor.
1053: .H log in\
1054: to identify one's self as a user and start a computing session.
1055: .H login\
1056: 1.\&
1057: the
1058: .C program
1059: that controls logging in.
1060: 2.\&
1061: the act of
1062: .C logging in.
1063: 3.\&
1064: by extension, the computing session that follows a login
1065: [2].
1066: .H login name\
1067: the name by which a person is identified when
1068: .C logging in;
1069: cf.\&
1070: .C userid.
1071: .H magic number\
1072: a
1073: .C cookie
1074: that distinguishes various flavors of
1075: .C object file;
1076: see
1077: .I a.out (5).
1078: .H major device\
1079: see
1080: .C device number.
1081: .H makefile, mkfile\
1082: a list of dependencies among files and recipes for updating
1083: them, usually by recompilation,
1084: used by
1085: .I make (1)
1086: or
1087: .I mk (1)
1088: to maintain self-consistent software;
1089: `mkfile' rhymes with `book file'.
1090: .H manager\
1091: same as
1092: .C server.
1093: .H memory image\
1094: same as
1095: .C core image.
1096: .H message line discipline\
1097: a
1098: .C line discipline
1099: used on
1100: .C pipes
1101: wherein a record of each
1102: .C system call
1103: on one end of the pipe is received as a message
1104: at the other end; see
1105: .I mesgld (4).
1106: .H minor device\
1107: see
1108: .C device number.
1109: .H mode, file mode\
1110: the
1111: .C permissions
1112: of a
1113: .C file;
1114: colloquially referred to by a 3-digit octal number, e.g. `a 755 file';
1115: see
1116: .I chmod (1).
1117: .H modification time\
1118: the most recent
1119: .C time
1120: at which the contents of a
1121: .C file
1122: [2] were altered;
1123: cf.\&
1124: .C access time,
1125: .C change time.
1126: .H mount\
1127: to associate with a
1128: .C directory entry
1129: [2] a
1130: .C stream
1131: [2] or the
1132: .C root
1133: [1]
1134: of a
1135: .C file system
1136: [1],
1137: making respectively a virtual file
1138: or an extended
1139: .C file system
1140: [2].
1141: Mounting assigns to the
1142: .C inode
1143: of a directory entry a temporary meaning,
1144: which ceases with the associated
1145: .C server
1146: [1],
1147: with explicit unmounting,
1148: or with
1149: .C booting.
1150: .H mounted stream\
1151: a
1152: .C directory entry
1153: [2] on which an open
1154: .C stream
1155: [2]
1156: has been
1157: .C mounted.
1158: .H named pipe\
1159: same as
1160: .C mounted stream.
1161: .H namelist\
1162: same as
1163: .C symbol table.
1164: .H network file system\
1165: a mechanism for cross-\c
1166: .C mounting
1167: the
1168: .C file systems
1169: [2] of different computers; see
1170: .I netfs (8).
1171: .H newline\
1172: the combined function of carriage return and line feed,
1173: represented by the
1174: ASCII
1175: character LF, octal value 012;
1176: separates
1177: .C lines
1178: in a
1179: .C text file;
1180: newline is evoked by the `return' key on most terminals.
1181: .H nice\
1182: to place a
1183: .C process
1184: in
1185: .C nice mode
1186: [2].
1187: .H nice mode\
1188: 1.\&
1189: the scheduling priority of a
1190: .C process;
1191: see
1192: .I nice (2).
1193: 2.\&
1194: in particular, a low priority.
1195: .H null device\
1196: a
1197: .C device
1198: [1] that always yields
1199: .C end of file
1200: on reading and discards all data on writing.
1201: .H null pointer\
1202: in C, a pointer object with value 0.
1203: .H object file\
1204: a
1205: .C file
1206: [2] that contains machine language code and data;
1207: object files are produced from source programs by compilers
1208: and from other object files and
1209: .C libraries
1210: by the
1211: .C link editor;
1212: an object file that is ready to run is an
1213: .C executable file
1214: [1].
1215: .H open\
1216: to make a
1217: .C file
1218: [2] available for writing or reading, with the
1219: .C file pointer
1220: positioned at byte 0;
1221: converse of
1222: .C close;
1223: cf.\&
1224: .C create.
1225: .H open file\
1226: 1.\&
1227: the destination for input or output obtained by
1228: .C opening
1229: a
1230: .C file
1231: [2] or creating a
1232: .C pipe;
1233: a
1234: .C file descriptor;
1235: open files are shared across
1236: .C forks
1237: and persist across
1238: .C executes
1239: [2].
1240: 2.\&
1241: loosely, a
1242: .C file
1243: [2]
1244: that has been opened.
1245: .H option\
1246: an
1247: .C argument
1248: that affects the way a
1249: .C command
1250: works; option names customarily begin with
1251: .CW - .
1252: .H ordinary file\
1253: same as
1254: .C plain file.
1255: .H other\
1256: 1.\&
1257: the category of
1258: .C permissions
1259: regulating access to a
1260: .C file
1261: [2] by processes with
1262: .C userid
1263: different from the
1264: .C owner
1265: and
1266: .C groupid
1267: different from the
1268: .C group
1269: of the file.
1270: 2.\&
1271: the customary name of the default
1272: .C group
1273: [2] assigned upon
1274: .C login
1275: [2].
1276: .H owner\
1277: a
1278: .C userid
1279: associated with a
1280: .C file
1281: [2], usually
1282: that of the
1283: .C process
1284: that created it;
1285: the owner has distinctive
1286: .C permissions
1287: for a file.
1288: .H page\
1289: a hardware-dependent unit of virtual memory management,
1290: defined in
1291: .CW /usr/include/sys/types.h ;
1292: cf.\&
1293: .C block.
1294: .H parent directory\
1295: the
1296: .C directory
1297: next nearer the
1298: .C root
1299: than a given directory;
1300: the inverse of a
1301: .C subdirectory.
1302: A
1303: .C directory entry
1304: [2]
1305: .CW ..
1306: always refers to the parent directory.
1307: .H parent process\
1308: see
1309: .C fork.
1310: .H password\
1311: a secret word used to confirm a user's right to
1312: .C log in
1313: under a particular
1314: .C userid;
1315: passwords are encrypted by a one-way algorithm and kept in the
1316: .C password file.
1317: .H password file\
1318: a record of all
1319: .C login names
1320: with the
1321: .C password,
1322: .C userid,
1323: .C groupid,
1324: .C home directory,
1325: and
1326: .C shell
1327: [2] for each, used to control access to the system.
1328: .H path, pathname\
1329: a chain of names designating a
1330: .C file;
1331: a
1332: .HI relative pathname
1333: leads from the
1334: .C current directory,
1335: for example, a path to
1336: .C directory
1337: .CW A ,
1338: thence to directory
1339: .CW B ,
1340: thence to
1341: .C file
1342: [2]
1343: .CW C
1344: is denoted
1345: .CW A/B/C ;
1346: a
1347: .HI full pathname
1348: begins at the
1349: .C root
1350: [2],
1351: indicated by an initial
1352: .CW / ,
1353: as in
1354: .CW /A/B/C .
1355: .H permission\
1356: a right to access a
1357: .C file
1358: [2] in a particular way: read, write, execute (or look up in, if a directory);
1359: permissions are granted separately to
1360: .C owner,
1361: .C group,
1362: and
1363: .C others.
1364: .HI permission bit\
1365: a permission, so called because each permission is encoded into
1366: one bit in an
1367: .C inode.
1368: .H pid\
1369: see
1370: .C process id.
1371: .H pipe\
1372: a nameless
1373: .C stream
1374: [2] connection between
1375: .C processes,
1376: whereby data written on an
1377: .C open file
1378: in one process may be read in another; cf.\&
1379: .C named pipe.
1380: .H pipeline\
1381: a sequence of
1382: .C programs
1383: [1]
1384: connected by
1385: .C pipes.
1386: .H plain file, ordinary file\
1387: a
1388: .C file
1389: [2] that is neither a
1390: .C special file
1391: nor a
1392: .C directory;
1393: plain files are the customary repository of data.
1394: .H priority\
1395: see
1396: .C nice mode
1397: [1].
1398: .H process\
1399: a connected sequence of computation;
1400: a process is characterized by a
1401: .C core image
1402: with instruction location counter,
1403: .C current directory,
1404: a set of
1405: .C open files,
1406: .C control stream,
1407: .C userid,
1408: and
1409: .C groupid.
1410: .H process directory\
1411: a
1412: .C special file system,
1413: .CW /proc ,
1414: in which all
1415: .C process files
1416: appear.
1417: .H process file\
1418: a
1419: .C core image
1420: of a
1421: .C process,
1422: accessible as a
1423: .C file
1424: [3].
1425: .H process group\
1426: a set of processes that share a
1427: .C control stream
1428: and among which
1429: .C signals
1430: may be broadcast;
1431: process groups are created upon
1432: .C logging in,
1433: creating a window, or
1434: issuing certain
1435: .C io controls;
1436: see
1437: .I stream (4).
1438: .H process number, process id, pid\
1439: an integer that identifies a
1440: .C process.
1441: .H profile\
1442: 1.\&
1443: an optional
1444: .C shell script,
1445: .CW \&.profile ,
1446: used by the
1447: .C shell
1448: [1] upon
1449: .C logging in
1450: to establish the
1451: .C environment
1452: [3]
1453: and other working conditions customary to a particular user.
1454: 2.\&
1455: to collect a histogram of values of the instruction location counter of a
1456: .C process;
1457: see
1458: .I monitor (3).
1459: .H program\
1460: 1.\&
1461: an
1462: .C executable file.
1463: 2.\&
1464: a
1465: .C process.
1466: 3.\&
1467: all the usual meanings.
1468: .H program break\
1469: the first address beyond the
1470: .C static
1471: data accessible to a
1472: .C process;
1473: the program break may be
1474: adjusted by
1475: .I brk (2).
1476: .H quit\
1477: a
1478: .C signal
1479: that normally terminates a
1480: .C process,
1481: caused by a
1482: .HI quit character
1483: (normally control-\e);
1484: quit differs from
1485: .C interrupt
1486: in that quit creates a
1487: .C core file
1488: for the terminated process.
1489: .H random library\
1490: a
1491: .C library
1492: that contains an index to
1493: .C external
1494: names;
1495: a library is made into a random library by
1496: .C ranlib
1497: see
1498: .I ar (1).
1499: Nonrandom libraries must be carefully ordered for the
1500: .C link editor
1501: to cope with cross references among the subroutines.
1502: .H raw\
1503: 1.\&
1504: a mode of terminal input in which every character typed is passed
1505: to a reading
1506: .C process
1507: and
1508: .C special characters
1509: lose their special character;
1510: converse of
1511: .C cooked.
1512: 2.\&
1513: said of input-output to a
1514: .C raw device.
1515: .H raw device\
1516: a
1517: .C device
1518: [1],
1519: read and write operations to which are not
1520: .C buffered,
1521: and are synchronized to natural records of the physical device.
1522: A raw device is usually a
1523: .C character device
1524: that addresses the same physical device as some
1525: .C block device.
1526: .H read ahead\
1527: to fill input
1528: .C buffers
1529: in the
1530: .C kernel
1531: in advance of
1532: .I read (2)
1533: operations.
1534: .H read pointer\
1535: same as
1536: .C file pointer.
1537: .H real userid\
1538: see
1539: .C set userid.
1540: .H reboot\
1541: same as
1542: .C boot.
1543: .H regular expression\
1544: 1.\&
1545: an expression denoting a set of strings in a notation due to Kleene.
1546: 2.\&
1547: especially,
1548: a restricted and modified form of regular expression used for pattern-matching in
1549: .I ed (1)
1550: and elsewhere.
1551: .H relative pathname\
1552: see
1553: .C pathname.
1554: .H relocation bits, relocation information\
1555: information in an
1556: .C object file
1557: that tells the
1558: .C link editor
1559: how to adjust addresses when combining it with other
1560: .C object files;
1561: `bits' is a fossilized misnomer.
1562: .H return code\
1563: same as
1564: .C exit status.
1565: .H root\
1566: 1.\&
1567: a distinguished directory that constitutes the origin of the
1568: .C directory hierarchy
1569: in a
1570: .C file system
1571: [1].
1572: 2.\&
1573: specifically, the origin for the
1574: .C file system
1575: [2], with the conventional
1576: .C pathname
1577: .CW / .
1578: 3.\&
1579: the conventional
1580: .C login name
1581: for the
1582: .C super-user.
1583: .H schedule\
1584: to assign resources \- main store and CPU time \- to
1585: .C processes.
1586: .HI scheduler\
1587: a permanent
1588: .C process,
1589: with
1590: .C process number
1591: 1, and associated
1592: .C kernel
1593: facilities that do scheduling.
1594: .H search path\
1595: a list of
1596: .C pathnames
1597: of
1598: .C directories
1599: that determines the meaning of a
1600: .C command
1601: [2] name.
1602: In one form of
1603: .C exec,
1604: a
1605: .C relative pathname
1606: is prefixed with members of
1607: the search path in turn until
1608: a pathname of an
1609: .C executable file
1610: [2] results.
1611: .H seek\
1612: to set the
1613: .C file pointer
1614: to a specified place in an
1615: .C open file.
1616: .H seek pointer\
1617: same as
1618: .C file pointer.
1619: .H segment\
1620: a contiguous range of the
1621: address space
1622: of a
1623: .C process
1624: with consistent store access capabilities; the four segments are
1625: (i) the
1626: .HI text segment,
1627: occupied by executable code,
1628: (ii) the
1629: .HI data segment,
1630: occupied by
1631: .C static
1632: data that is
1633: explicitly initialized,
1634: (iii) the
1635: .HI bss segment,
1636: occupied by static data that is
1637: implicitly initialized to zero values
1638: (the name comes from a 1950's assembler), and
1639: (iv) the
1640: .HI stack segment,
1641: occupied by
1642: .C automatic
1643: data, see
1644: .C stack;
1645: sometimes (ii), (iii), and (iv) are collectively called data segments.
1646: .H server\
1647: 1.\&
1648: a
1649: .C process,
1650: usually permanent, that serves
1651: .C clients
1652: through a
1653: .C mounted
1654: interface, either a
1655: .C stream
1656: or a
1657: .C special file system.
1658: 2.\&
1659: a program, often a server
1660: [1],
1661: accessed via a distinctive
1662: network address to provide some
1663: remote computing service.
1664: .H set userid\
1665: a special
1666: .C permission
1667: for an
1668: .C executable file
1669: [1] that causes a
1670: .C process
1671: executing it
1672: to have the access rights of the
1673: .C owner
1674: of the file;
1675: the owner's
1676: .C userid
1677: becomes the
1678: .HI effective userid
1679: of the process, distinguished from the
1680: .HI real userid
1681: under which the process began.
1682: .HI set userid bit\
1683: the associated
1684: .C permission bit.
1685: .H shared text\
1686: a
1687: .C text segment,
1688: one copy of which may be used simultaneously by more than one
1689: .C process.
1690: .H shell\
1691: 1.\&
1692: the program
1693: .I sh (1),
1694: which causes other programs
1695: to be executed on
1696: .C command
1697: [2];
1698: the shell is usually started on a user's behalf upon
1699: .C logging in.
1700: 2.\&
1701: by analogy, any program started upon logging in.
1702: .H shell script, command file\
1703: a
1704: .C file
1705: [2] of
1706: .C commands
1707: taken as input to the
1708: .C shell
1709: [1].
1710: .H signal\
1711: an exceptional occurrence that causes a
1712: .C process
1713: to terminate or divert from the normal flow of control; cf.\&
1714: .C interrupt,
1715: .C kill.
1716: .H sleep\
1717: to cease activity for a specified time, or until a
1718: .C signal
1719: occurs, said of a
1720: .C process.
1721: .H soft link\
1722: same as
1723: .C symbolic link.
1724: .H spawn\
1725: to cause a
1726: .C program
1727: to be run in a
1728: .C child process;
1729: cf.\&
1730: .C fork, execute.
1731: .H special character\
1732: a character, which, when typed
1733: at a terminal, modifies the input or affects the behavior of
1734: .C processes
1735: for which that terminal is the
1736: .C control terminal;
1737: examples are the
1738: .C interrupt character,
1739: .C erase character,
1740: and
1741: .C EOT character.
1742: .H special file\
1743: an
1744: .C inode
1745: that designates a
1746: .C device,
1747: further categorized as either
1748: (i) a
1749: .HI block special file
1750: describing a
1751: .C block device,
1752: or (ii) a
1753: .HI character special file
1754: describing a
1755: .C character device.
1756: .H special file system\
1757: 1.\&
1758: a virtual
1759: .C directory,
1760: in which
1761: .C `entries'
1762: are constructed as needed.
1763: Examples are
1764: .CW /n ,
1765: the
1766: .C network file system,
1767: and
1768: .CW /proc ,
1769: the
1770: .C process directory.
1771: .H spool\
1772: to collect and serialize output from multiple
1773: .C processes
1774: competing
1775: for a single output service.
1776: .HI spooler\
1777: a
1778: .C daemon
1779: that spools.
1780: .HI spool area\
1781: a
1782: .C directory
1783: in which a
1784: spooler collects work.
1785: .H stack, stack segment\
1786: a
1787: .C segment
1788: of the address space into which
1789: .C automatic
1790: data and subroutine linkage information is allocated in
1791: last-in-first-out fashion;
1792: the stack occupies the largest data addresses and grows downward
1793: towards
1794: .C static
1795: data.
1796: .H standard input, standard output, standard error\
1797: .C open files,
1798: customarily available when a
1799: .C process
1800: begins, with
1801: .C file descriptors
1802: 0, 1, 2 and
1803: .C stdio
1804: names
1805: .CW stdin ,
1806: .CW stdout ,
1807: .CW stderr .
1808: Where possible, utilities by default read from the
1809: standard input, write on the standard output, and place
1810: error comments on the standard error file.
1811: .H standard input-output\
1812: see
1813: .C stdio.
1814: .H start/stop protocol, XON-XOFF protocol\
1815: a communication flow-control method in which a received
1816: .C special character,
1817: the
1818: .HI stop character,
1819: causes output to be suspended, and a received
1820: .HI start character
1821: causes output to be resumed.
1822: The default start and stop characters are ASCII DC1 (octal 022, control-Q)
1823: and DC3 (octal 024, control S) respectively.
1824: .H static\
1825: persistent throughout a process,
1826: said of data;
1827: static data occupies the
1828: .C data segment
1829: and the
1830: .C bss segment;
1831: cf.\&
1832: .C automatic.
1833: .H status\
1834: see
1835: .C exit status.
1836: .H stdio, standard input-output\
1837: a collection of functions for formatted and character-by-character
1838: input-output at a higher level than the basic
1839: .I read (2),
1840: .I write,
1841: and
1842: .I open (2)
1843: operations.
1844: .H stream\
1845: 1.\&
1846: an
1847: .C open file
1848: with
1849: .C buffering
1850: superimposed by the
1851: .C stdio
1852: package.
1853: 2.\&
1854: a bidirectional input-output connection between a
1855: .C process
1856: and a
1857: .C character device
1858: or another process.
1859: .H strip\
1860: remove the
1861: .C symbol table
1862: and
1863: .C relocation bits
1864: from an
1865: .C executable file
1866: [1].
1867: .H subdirectory\
1868: a
1869: .C directory
1870: that appears as an
1871: .C entry
1872: [1] in another.
1873: .H subshell\
1874: another copy of the
1875: .C shell
1876: [1], with its own
1877: .C environment
1878: and
1879: .C open files,
1880: run as a
1881: .C child process
1882: of the shell;
1883: .C shell scripts
1884: and commands subject to
1885: .CW for
1886: and
1887: .CW while
1888: or
1889: enclosed in parentheses
1890: .CW ()
1891: are normally run by subshells.
1892: .H super-block\
1893: the second
1894: .C block
1895: in a
1896: .C file system
1897: [1],
1898: which describes the allocation of space in the file system; cf.\&
1899: .C boot block.
1900: .H super-user\
1901: .C userid
1902: 0, which can access any
1903: .C file
1904: [2] regardless of
1905: .C permissions
1906: and can perform privileged
1907: .C system calls,
1908: e.g. to set the clock.
1909: .H swap\
1910: to move the
1911: .C core image
1912: of an executing program between main and secondary store to
1913: make room for other
1914: .C processes.
1915: .H swap area\
1916: the part of secondary store to which
1917: .C core images
1918: are
1919: .C swapped;
1920: the swap area is disjoint from
1921: .C file systems
1922: [1].
1923: .H symbolic link\
1924: an
1925: .C inode
1926: that contains the
1927: .C pathname
1928: of another.
1929: References to the symbolic link become references to
1930: the named inode.
1931: .H symbol table\
1932: information in an
1933: .C object file
1934: about the names
1935: of data and functions in that file;
1936: the symbol table and
1937: .C relocation bits
1938: are used by the
1939: .C link editor
1940: and by debuggers.
1941: .H system call\
1942: a basic operation performed by the
1943: .C kernel;
1944: see
1945: .I intro (2).
1946: .H system time\
1947: the accumulated time spent by a
1948: .C process
1949: in
1950: .C kernel
1951: code; cf.\&
1952: .C user time.
1953: .H tandem\
1954: a mode of the
1955: .C terminal line discipline
1956: in which the computer uses
1957: .C start/stop protocol
1958: to regulate data flow from another terminal or other computer.
1959: .H terminal line discipline, teletype line discipline\
1960: a
1961: .C line discipline
1962: that implements input-output features such as
1963: .C erase character
1964: and
1965: .C raw mode;
1966: see
1967: .I ttyld (4).
1968: .H terminal process\
1969: a program downloaded into a
1970: .C layer,
1971: often in collaboration with a
1972: .C host process.
1973: Running in a different environment, a
1974: terminal process is not a UNIX
1975: .C process.
1976: .H text\
1977: see
1978: .C text file,
1979: .C segment.
1980: .H text file, ASCII file\
1981: a
1982: .C file,
1983: the bytes of which are understood to be in
1984: ASCII
1985: code.
1986: .H text segment\
1987: see
1988: .C segment.
1989: .H time\
1990: the number of seconds since the
1991: .HI epoch\fR,
1992: 00:00:00 Greenwich Mean Time, January 1, 1970.
1993: .H u-area\
1994: a collection of data about, but not in the address space of, a
1995: .C process;
1996: the u-area is kept with the
1997: .C core image
1998: of the process.
1999: .H uid\
2000: see
2001: .C userid.
2002: .H umask\
2003: a list of
2004: .C permissions
2005: that will be denied for files
2006: .C created
2007: by a
2008: .C process,
2009: so called because the list is expressed as a
2010: .C mode
2011: bit mask.
2012: .H UNIX\
2013: the name of a family of systems software,
2014: not an acronym for anything;
2015: a registered trademark of AT&T, the word should be used
2016: as an adjective, e.g. `UNIX system' or `UNIX software'.
2017: Major genera are the
2018: research versions issued as numbered `editions', the
2019: Berkeley software distributions (BSD), and the commercial
2020: System V.
2021: .H unlink\
2022: to remove an
2023: .C entry
2024: [1] from a
2025: .C directory;
2026: converse to
2027: .C link
2028: and
2029: .C create.
2030: .H upas\
2031: 1.\&
2032: a fabulous Javanese tree that poisoned everything
2033: for miles around.
2034: 2.\&
2035: a routing and delivery system for electronic mail.
2036: .H URP\
2037: universal receiver protocol used by
2038: .C Datakit.
2039: .H usenet\
2040: an informal, nationwide computer network based on
2041: .I uucp (1),
2042: over which
2043: `netnews'
2044: is distributed; see
2045: .I readnews (7).
2046: .H user code\
2047: code that runs in a
2048: .C process,
2049: as distinct from
2050: .C kernel
2051: code.
2052: .H userid, uid\
2053: an integer value, usually associated with a
2054: .C login name;
2055: the userid of a
2056: .C process
2057: becomes the
2058: .C owner
2059: of files
2060: .C created
2061: by the process; it is inherited
2062: across
2063: .C fork.
2064: .H user space, user address space\
2065: the address space of a
2066: .C process,
2067: as distinct from
2068: .C kernel space.
2069: The address spaces of different processes are
2070: mutually disjoint.
2071: .H user time\
2072: the accumulated time spent by a
2073: .C process
2074: in
2075: .C user code;
2076: cf.\&
2077: .C system time.
2078: .H utility, utility program\
2079: a standard, generally useful, permanently available
2080: .C program;
2081: utilities normally inhabit directories
2082: .CW /bin
2083: and
2084: .CW /usr/bin .
2085: .H wait\
2086: to suspend running until the termination of another
2087: .C process;
2088: only a
2089: .C parent process
2090: can wait for one of its
2091: .C child processes.
2092: .H window\
2093: 1.\&
2094: same as
2095: .C layer.
2096: 2.\&
2097: a sublayer in
2098: .C terminal processes
2099: such as
2100: .I pi (9)
2101: or
2102: .I sam (9).
2103: .H working directory\
2104: same as
2105: .C current directory.
2106: .H write behind\
2107: to
2108: .C buffer
2109: data for writing to a
2110: .C device
2111: [2] at a convenient time without holding up the computation
2112: of a writing
2113: .C process.
2114: .H write pointer\
2115: same as
2116: .C file pointer.
2117: .H XON-XOFF protocol\
2118: same as
2119: .C start/stop protocol.
2120: .H zombie\
2121: a terminated
2122: .C process
2123: with a running
2124: .C parent process
2125: that has not
2126: .C waited
2127: for it.
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