1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
|
@menu
* Introduction:: Purpose of the GNU C Library.
* Error Reporting:: How library functions report errors.
* Memory Allocation:: Allocating memory dynamically and
manipulating it via pointers.
* Character Handling:: Character testing and conversion functions.
* String and Array Utilities:: Utilities for copying and comparing strings
and arrays.
* Extended Characters:: Support for extended character sets.
* Locales:: The country and language can affect the
behavior of library functions.
* Message Translation:: How to make the program speak the user's
language.
* Searching and Sorting:: General searching and sorting functions.
* Pattern Matching:: Matching shell ``globs'' and regular
expressions.
* I/O Overview:: Introduction to the I/O facilities.
* I/O on Streams:: Hign-level, portable I/O facilities.
* Low-Level I/O:: Low-level, less portable I/O.
* File System Interface:: Functions for manipulating files.
* Pipes and FIFOs:: A simple interprocess communication
mechanism.
* Sockets:: A more complicated IPC mechanism, with
networking support.
* Low-Level Terminal Interface:: How to change the characteristics of a
terminal device.
* Mathematics:: Math functions, useful constants, random
numbers.
* Arithmetic:: Low level arithmetic functions.
* Date and Time:: Functions for getting the date and time and
formatting them nicely.
* Non-Local Exits:: Jumping out of nested function calls.
* Signal Handling:: How to send, block, and handle signals.
* Process Startup:: Writing the beginning and end of your
program.
* Processes:: How to create processes and run other
programs.
* Job Control:: All about process groups and sessions.
* Name Service Switch:: Accessing system databases.
* Users and Groups:: How users are identified and classified.
* System Information:: Getting information about the hardware and
operating system.
* System Configuration:: Parameters describing operating system
limits.
Add-ons
* POSIX Threads:: The standard threads library.
Appendices
* Language Features:: C language features provided by the library.
* Library Summary:: A summary showing the syntax, header file,
and derivation of each library feature.
* Installation:: How to install the GNU C library.
* Maintenance:: How to enhance and port the GNU C Library.
* Contributors:: Who wrote what parts of the GNU C library.
* Copying:: The GNU Library General Public License says
how you can copy and share the GNU C Library.
Indices
* Concept Index:: Index of concepts and names.
* Type Index:: Index of types and type qualifiers.
* Function Index:: Index of functions and function-like macros.
* Variable Index:: Index of variables and variable-like macros.
* File Index:: Index of programs and files.
--- The Detailed Node Listing ---
Introduction
* Getting Started:: What this manual is for and how to use it.
* Standards and Portability:: Standards and sources upon which the GNU
C library is based.
* Using the Library:: Some practical uses for the library.
* Roadmap to the Manual:: Overview of the remaining chapters in
this manual.
Standards and Portability
* ISO C:: The international standard for the C
programming language.
* POSIX:: The ISO/IEC 9945 (aka IEEE 1003) standards
for operating systems.
* Berkeley Unix:: BSD and SunOS.
* SVID:: The System V Interface Description.
* XPG:: The X/Open Portability Guide.
Using the Library
* Header Files:: How to include the header files in your
programs.
* Macro Definitions:: Some functions in the library may really
be implemented as macros.
* Reserved Names:: The C standard reserves some names for
the library, and some for users.
* Feature Test Macros:: How to control what names are defined.
Error Reporting
* Checking for Errors:: How errors are reported by library functions.
* Error Codes:: Error code macros; all of these expand
into integer constant values.
* Error Messages:: Mapping error codes onto error messages.
Memory Allocation
* Memory Concepts:: An introduction to concepts and terminology.
* Dynamic Allocation and C:: How to get different kinds of allocation in C.
* Unconstrained Allocation:: The @code{malloc} facility allows fully general
dynamic allocation.
* Allocation Debugging:: Finding memory leaks and not freed memory.
* Obstacks:: Obstacks are less general than malloc
but more efficient and convenient.
* Variable Size Automatic:: Allocation of variable-sized blocks
of automatic storage that are freed when the
calling function returns.
Unconstrained Allocation
* Basic Allocation:: Simple use of @code{malloc}.
* Malloc Examples:: Examples of @code{malloc}. @code{xmalloc}.
* Freeing after Malloc:: Use @code{free} to free a block you
got with @code{malloc}.
* Changing Block Size:: Use @code{realloc} to make a block
bigger or smaller.
* Allocating Cleared Space:: Use @code{calloc} to allocate a
block and clear it.
* Efficiency and Malloc:: Efficiency considerations in use of
these functions.
* Aligned Memory Blocks:: Allocating specially aligned memory:
@code{memalign} and @code{valloc}.
* Malloc Tunable Parameters:: Use @code{mallopt} to adjust allocation
parameters.
* Heap Consistency Checking:: Automatic checking for errors.
* Hooks for Malloc:: You can use these hooks for debugging
programs that use @code{malloc}.
* Statistics of Malloc:: Getting information about how much
memory your program is using.
* Summary of Malloc:: Summary of @code{malloc} and related functions.
Allocation Debugging
* Tracing malloc:: How to install the tracing functionality.
* Using the Memory Debugger:: Example programs excerpts.
* Tips for the Memory Debugger:: Some more or less clever ideas.
* Interpreting the traces:: What do all these lines mean?
Obstacks
* Creating Obstacks:: How to declare an obstack in your program.
* Preparing for Obstacks:: Preparations needed before you can
use obstacks.
* Allocation in an Obstack:: Allocating objects in an obstack.
* Freeing Obstack Objects:: Freeing objects in an obstack.
* Obstack Functions:: The obstack functions are both
functions and macros.
* Growing Objects:: Making an object bigger by stages.
* Extra Fast Growing:: Extra-high-efficiency (though more
complicated) growing objects.
* Status of an Obstack:: Inquiries about the status of an obstack.
* Obstacks Data Alignment:: Controlling alignment of objects in obstacks.
* Obstack Chunks:: How obstacks obtain and release chunks;
efficiency considerations.
* Summary of Obstacks::
Variable Size Automatic
* Alloca Example:: Example of using @code{alloca}.
* Advantages of Alloca:: Reasons to use @code{alloca}.
* Disadvantages of Alloca:: Reasons to avoid @code{alloca}.
* GNU C Variable-Size Arrays:: Only in GNU C, here is an alternative
method of allocating dynamically and
freeing automatically.
Character Handling
* Classification of Characters:: Testing whether characters are
letters, digits, punctuation, etc.
* Case Conversion:: Case mapping, and the like.
String and Array Utilities
* Representation of Strings:: Introduction to basic concepts.
* String/Array Conventions:: Whether to use a string function or an
arbitrary array function.
* String Length:: Determining the length of a string.
* Copying and Concatenation:: Functions to copy the contents of strings
and arrays.
* String/Array Comparison:: Functions for byte-wise and character-wise
comparison.
* Collation Functions:: Functions for collating strings.
* Search Functions:: Searching for a specific element or substring.
* Finding Tokens in a String:: Splitting a string into tokens by looking
for delimiters.
* Encode Binary Data:: Encoding and Decoding of Binary Data.
* Argz and Envz Vectors:: Null-separated string vectors.
Argz and Envz Vectors
* Argz Functions:: Operations on argz vectors.
* Envz Functions:: Additional operations on environment vectors.
Extended Characters
* Extended Char Intro:: Multibyte codes versus wide characters.
* Locales and Extended Chars:: The locale selects the character codes.
* Multibyte Char Intro:: How multibyte codes are represented.
* Wide Char Intro:: How wide characters are represented.
* Wide String Conversion:: Converting wide strings to multibyte code
and vice versa.
* Length of Char:: how many bytes make up one multibyte char.
* Converting One Char:: Converting a string character by character.
* Example of Conversion:: Example showing why converting
one character at a time may be useful.
* Shift State:: Multibyte codes with "shift characters".
Locales
* Effects of Locale:: Actions affected by the choice of
locale.
* Choosing Locale:: How the user specifies a locale.
* Locale Categories:: Different purposes for which you can
select a locale.
* Setting the Locale:: How a program specifies the locale
with library functions.
* Standard Locales:: Locale names available on all systems.
* Locale Information:: How to access the information for the locale.
* Formatting Numbers:: A dedicated function to format numbers.
Locale Information
* The Lame Way to Locale Data:: ISO C's @code{localeconv}.
* The Elegant and Fast Way:: X/Open's @code{nl_langinfo}.
The Lame Way to Locale Data
* General Numeric:: Parameters for formatting numbers and
currency amounts.
* Currency Symbol:: How to print the symbol that identifies an
amount of money (e.g. @samp{$}).
* Sign of Money Amount:: How to print the (positive or negative) sign
for a monetary amount, if one exists.
Message Translation
* Message catalogs a la X/Open:: The @code{catgets} family of functions.
* The Uniforum approach:: The @code{gettext} family of functions.
Message catalogs a la X/Open
* The catgets Functions:: The @code{catgets} function family.
* The message catalog files:: Format of the message catalog files.
* The gencat program:: How to generate message catalogs files which
can be used by the functions.
* Common Usage:: How to use the @code{catgets} interface.
The Uniforum approach
* Message catalogs with gettext:: The @code{gettext} family of functions.
* Helper programs for gettext:: Programs to handle message catalogs
for @code{gettext}.
Message catalogs with gettext
* Translation with gettext:: What has to be done to translate a message.
* Locating gettext catalog:: How to determine which catalog to be used.
* Using gettextized software:: The possibilities of the user to influence
the way @code{gettext} works.
Searching and Sorting
* Comparison Functions:: Defining how to compare two objects.
Since the sort and search facilities
are general, you have to specify the
ordering.
* Array Search Function:: The @code{bsearch} function.
* Array Sort Function:: The @code{qsort} function.
* Search/Sort Example:: An example program.
* Hash Search Function:: The @code{hsearch} function.
* Tree Search Function:: The @code{tsearch} function.
Pattern Matching
* Wildcard Matching:: Matching a wildcard pattern against a single string.
* Globbing:: Finding the files that match a wildcard pattern.
* Regular Expressions:: Matching regular expressions against strings.
* Word Expansion:: Expanding shell variables, nested commands,
arithmetic, and wildcards.
This is what the shell does with shell commands.
Globbing
* Calling Glob:: Basic use of @code{glob}.
* Flags for Globbing:: Flags that enable various options in @code{glob}.
* More Flags for Globbing:: GNU specific extensions to @code{glob}.
Regular Expressions
* POSIX Regexp Compilation:: Using @code{regcomp} to prepare to match.
* Flags for POSIX Regexps:: Syntax variations for @code{regcomp}.
* Matching POSIX Regexps:: Using @code{regexec} to match the compiled
pattern that you get from @code{regcomp}.
* Regexp Subexpressions:: Finding which parts of the string were matched.
* Subexpression Complications:: Find points of which parts were matched.
* Regexp Cleanup:: Freeing storage; reporting errors.
Word Expansion
* Expansion Stages:: What word expansion does to a string.
* Calling Wordexp:: How to call @code{wordexp}.
* Flags for Wordexp:: Options you can enable in @code{wordexp}.
* Wordexp Example:: A sample program that does word expansion.
* Tilde Expansion:: Details of how tilde expansion works.
* Variable Substitution:: Different types of variable substitution.
I/O Overview
* I/O Concepts:: Some basic information and terminology.
* File Names:: How to refer to a file.
I/O Concepts
* Streams and File Descriptors:: The GNU Library provides two ways
to access the contents of files.
* File Position:: The number of bytes from the
beginning of the file.
File Names
* Directories:: Directories contain entries for files.
* File Name Resolution:: A file name specifies how to look up a file.
* File Name Errors:: Error conditions relating to file names.
* File Name Portability:: File name portability and syntax issues.
I/O on Streams
* Streams:: About the data type representing a stream.
* Standard Streams:: Streams to the standard input and output
devices are created for you.
* Opening Streams:: How to create a stream to talk to a file.
* Closing Streams:: Close a stream when you are finished with it.
* Simple Output:: Unformatted output by characters and lines.
* Character Input:: Unformatted input by characters and words.
* Line Input:: Reading a line or a record from a stream.
* Unreading:: Peeking ahead/pushing back input just read.
* Block Input/Output:: Input and output operations on blocks of data.
* Formatted Output:: @code{printf} and related functions.
* Customizing Printf:: You can define new conversion specifiers for
@code{printf} and friends.
* Formatted Input:: @code{scanf} and related functions.
* EOF and Errors:: How you can tell if an I/O error happens.
* Binary Streams:: Some systems distinguish between text files
and binary files.
* File Positioning:: About random-access streams.
* Portable Positioning:: Random access on peculiar ISO C systems.
* Stream Buffering:: How to control buffering of streams.
* Other Kinds of Streams:: Streams that do not necessarily correspond
to an open file.
* Formatted Messages:: Print strictly formatted messages.
Unreading
* Unreading Idea:: An explanation of unreading with pictures.
* How Unread:: How to call @code{ungetc} to do unreading.
Formatted Output
* Formatted Output Basics:: Some examples to get you started.
* Output Conversion Syntax:: General syntax of conversion
specifications.
* Table of Output Conversions:: Summary of output conversions and
what they do.
* Integer Conversions:: Details about formatting of integers.
* Floating-Point Conversions:: Details about formatting of
floating-point numbers.
* Other Output Conversions:: Details about formatting of strings,
characters, pointers, and the like.
* Formatted Output Functions:: Descriptions of the actual functions.
* Dynamic Output:: Functions that allocate memory for the output.
* Variable Arguments Output:: @code{vprintf} and friends.
* Parsing a Template String:: What kinds of args does a given template
call for?
* Example of Parsing:: Sample program using @code{parse_printf_format}.
Customizing Printf
* Registering New Conversions:: Using @code{register_printf_function}
to register a new output conversion.
* Conversion Specifier Options:: The handler must be able to get
the options specified in the
template when it is called.
* Defining the Output Handler:: Defining the handler and arginfo
functions that are passed as arguments
to @code{register_printf_function}.
* Printf Extension Example:: How to define a @code{printf}
handler function.
* Predefined Printf Handlers:: Predefined @code{printf} handlers.
Formatted Input
* Formatted Input Basics:: Some basics to get you started.
* Input Conversion Syntax:: Syntax of conversion specifications.
* Table of Input Conversions:: Summary of input conversions and what they do.
* Numeric Input Conversions:: Details of conversions for reading numbers.
* String Input Conversions:: Details of conversions for reading strings.
* Dynamic String Input:: String conversions that @code{malloc} the buffer.
* Other Input Conversions:: Details of miscellaneous other conversions.
* Formatted Input Functions:: Descriptions of the actual functions.
* Variable Arguments Input:: @code{vscanf} and friends.
Stream Buffering
* Buffering Concepts:: Terminology is defined here.
* Flushing Buffers:: How to ensure that output buffers are flushed.
* Controlling Buffering:: How to specify what kind of buffering to use.
Other Kinds of Streams
* String Streams:: Streams that get data from or put data in
a string or memory buffer.
* Obstack Streams:: Streams that store data in an obstack.
* Custom Streams:: Defining your own streams with an arbitrary
input data source and/or output data sink.
Custom Streams
* Streams and Cookies:: The @dfn{cookie} records where to fetch or
store data that is read or written.
* Hook Functions:: How you should define the four @dfn{hook
functions} that a custom stream needs.
Formatted Messages
* Printing Formatted Messages:: The @code{fmtmsg} function.
* Adding Severity Classes:: Add more severity classes.
* Example:: How to use @code{fmtmsg} and @code{addseverity}.
Low-Level I/O
* Opening and Closing Files:: How to open and close file
descriptors.
* Truncating Files:: Change the size of a file.
* I/O Primitives:: Reading and writing data.
* File Position Primitive:: Setting a descriptor's file
position.
* Descriptors and Streams:: Converting descriptor to stream
or vice-versa.
* Stream/Descriptor Precautions:: Precautions needed if you use both
descriptors and streams.
* Scatter-Gather:: Fast I/O to discontinous buffers.
* Memory-mapped I/O:: Using files like memory.
* Waiting for I/O:: How to check for input or output
on multiple file descriptors.
* Synchronizing I/O:: Making sure all I/O actions completed.
* Asynchronous I/O:: Perform I/O in parallel.
* Control Operations:: Various other operations on file
descriptors.
* Duplicating Descriptors:: Fcntl commands for duplicating
file descriptors.
* Descriptor Flags:: Fcntl commands for manipulating
flags associated with file
descriptors.
* File Status Flags:: Fcntl commands for manipulating
flags associated with open files.
* File Locks:: Fcntl commands for implementing
file locking.
* Interrupt Input:: Getting an asynchronous signal when
input arrives.
* IOCTLs:: Generic I/O Control operations.
Stream/Descriptor Precautions
* Linked Channels:: Dealing with channels sharing a file position.
* Independent Channels:: Dealing with separately opened, unlinked channels.
* Cleaning Streams:: Cleaning a stream makes it safe to use
another channel.
Asynchronous I/O
* Asynchronous Reads/Writes:: Asynchronous Read and Write Operations.
* Status of AIO Operations:: Getting the Status of AIO Operations.
* Synchronizing AIO Operations:: Getting into a consistent state.
* Cancel AIO Operations:: Cancelation of AIO Operations.
* Configuration of AIO:: How to optimize the AIO implementation.
File Status Flags
* Access Modes:: Whether the descriptor can read or write.
* Open-time Flags:: Details of @code{open}.
* Operating Modes:: Special modes to control I/O operations.
* Getting File Status Flags:: Fetching and changing these flags.
File System Interface
* Working Directory:: This is used to resolve relative
file names.
* Accessing Directories:: Finding out what files a directory
contains.
* Working on Directory Trees:: Apply actions to all files or a selectable
subset of a directory hierarchy.
* Hard Links:: Adding alternate names to a file.
* Symbolic Links:: A file that ``points to'' a file name.
* Deleting Files:: How to delete a file, and what that means.
* Renaming Files:: Changing a file's name.
* Creating Directories:: A system call just for creating a directory.
* File Attributes:: Attributes of individual files.
* Making Special Files:: How to create special files.
* Temporary Files:: Naming and creating temporary files.
Accessing Directories
* Directory Entries:: Format of one directory entry.
* Opening a Directory:: How to open a directory stream.
* Reading/Closing Directory:: How to read directory entries from the stream.
* Simple Directory Lister:: A very simple directory listing program.
* Random Access Directory:: Rereading part of the directory
already read with the same stream.
* Scanning Directory Content:: Get entries for user selected subset of
contents in given directory.
* Simple Directory Lister Mark II:: Revised version of the program.
File Attributes
* Attribute Meanings:: The names of the file attributes,
and what their values mean.
* Reading Attributes:: How to read the attributes of a file.
* Testing File Type:: Distinguishing ordinary files,
directories, links...
* File Owner:: How ownership for new files is determined,
and how to change it.
* Permission Bits:: How information about a file's access
mode is stored.
* Access Permission:: How the system decides who can access a file.
* Setting Permissions:: How permissions for new files are assigned,
and how to change them.
* Testing File Access:: How to find out if your process can
access a file.
* File Times:: About the time attributes of a file.
* File Size:: Manually changing the size of a file.
Pipes and FIFOs
* Creating a Pipe:: Making a pipe with the @code{pipe} function.
* Pipe to a Subprocess:: Using a pipe to communicate with a
child process.
* FIFO Special Files:: Making a FIFO special file.
* Pipe Atomicity:: When pipe (or FIFO) I/O is atomic.
Sockets
* Socket Concepts:: Basic concepts you need to know about.
* Communication Styles::Stream communication, datagrams, and other styles.
* Socket Addresses:: How socket names (``addresses'') work.
* Interface Naming:: Identifying specific network interfaces.
* Local Namespace:: Details about the local namespace.
* Internet Namespace:: Details about the Internet namespace.
* Misc Namespaces:: Other namespaces not documented fully here.
* Open/Close Sockets:: Creating sockets and destroying them.
* Connections:: Operations on sockets with connection state.
* Datagrams:: Operations on datagram sockets.
* Inetd:: Inetd is a daemon that starts servers on request.
The most convenient way to write a server
is to make it work with Inetd.
* Socket Options:: Miscellaneous low-level socket options.
* Networks Database:: Accessing the database of network names.
Socket Addresses
* Address Formats:: About @code{struct sockaddr}.
* Setting Address:: Binding an address to a socket.
* Reading Address:: Reading the address of a socket.
Local Namespace
* Concepts: Local Namespace Concepts. What you need to understand.
* Details: Local Namespace Details. Address format, symbolic names, etc.
* Example: Local Socket Example. Example of creating a socket.
Internet Namespace
* Internet Address Formats:: How socket addresses are specified in the
Internet namespace.
* Host Addresses:: All about host addresses of internet host.
* Protocols Database:: Referring to protocols by name.
* Ports:: Internet port numbers.
* Services Database:: Ports may have symbolic names.
* Byte Order:: Different hosts may use different byte
ordering conventions; you need to
canonicalize host address and port number.
* Inet Example:: Putting it all together.
Host Addresses
* Abstract Host Addresses:: What a host number consists of.
* Data type: Host Address Data Type. Data type for a host number.
* Functions: Host Address Functions. Functions to operate on them.
* Names: Host Names. Translating host names to host numbers.
Open/Close Sockets
* Creating a Socket:: How to open a socket.
* Closing a Socket:: How to close a socket.
* Socket Pairs:: These are created like pipes.
Connections
* Connecting:: What the client program must do.
* Listening:: How a server program waits for requests.
* Accepting Connections:: What the server does when it gets a request.
* Who is Connected:: Getting the address of the
other side of a connection.
* Transferring Data:: How to send and receive data.
* Byte Stream Example:: An example program: a client for communicating
over a byte stream socket in the Internet namespace.
* Server Example:: A corresponding server program.
* Out-of-Band Data:: This is an advanced feature.
Transferring Data
* Sending Data:: Sending data with @code{send}.
* Receiving Data:: Reading data with @code{recv}.
* Socket Data Options:: Using @code{send} and @code{recv}.
Datagrams
* Sending Datagrams:: Sending packets on a datagram socket.
* Receiving Datagrams:: Receiving packets on a datagram socket.
* Datagram Example:: An example program: packets sent over a
datagram socket in the local namespace.
* Example Receiver:: Another program, that receives those packets.
Inetd
* Inetd Servers::
* Configuring Inetd::
Socket Options
* Socket Option Functions:: The basic functions for setting and getting
socket options.
* Socket-Level Options:: Details of the options at the socket level.
Low-Level Terminal Interface
* Is It a Terminal:: How to determine if a file is a terminal
device, and what its name is.
* I/O Queues:: About flow control and typeahead.
* Canonical or Not:: Two basic styles of input processing.
* Terminal Modes:: How to examine and modify flags controlling
details of terminal I/O: echoing,
signals, editing.
* Line Control:: Sending break sequences, clearing
terminal buffers @dots{}
* Noncanon Example:: How to read single characters without echo.
* Pseudo-Terminals:: How to open a pseudo-terminal.
Terminal Modes
* Mode Data Types:: The data type @code{struct termios} and
related types.
* Mode Functions:: Functions to read and set the terminal
attributes.
* Setting Modes:: The right way to set terminal attributes
reliably.
* Input Modes:: Flags controlling low-level input handling.
* Output Modes:: Flags controlling low-level output handling.
* Control Modes:: Flags controlling serial port behavior.
* Local Modes:: Flags controlling high-level input handling.
* Line Speed:: How to read and set the terminal line speed.
* Special Characters:: Characters that have special effects,
and how to change them.
* Noncanonical Input:: Controlling how long to wait for input.
Special Characters
* Editing Characters:: Special characters that terminate lines and
delete text, and other editing functions.
* Signal Characters:: Special characters that send or raise signals
to or for certain classes of processes.
* Start/Stop Characters:: Special characters that suspend or resume
suspended output.
* Other Special:: Other special characters for BSD systems:
they can discard output, and print status.
Pseudo-Terminals
* Allocation:: Allocating a pseudo terminal.
* Pseudo-Terminal Pairs:: How to open both sides of a
pseudo-terminal in a single operation.
Mathematics
* Mathematical Constants:: Precise numeric values for often-used
constants.
* Trig Functions:: Sine, cosine, tangent, and friends.
* Inverse Trig Functions:: Arcsine, arccosine, etc.
* Exponents and Logarithms:: Also pow and sqrt.
* Hyperbolic Functions:: sinh, cosh, tanh, etc.
* Special Functions:: Bessel, gamma, erf.
* Pseudo-Random Numbers:: Functions for generating pseudo-random
numbers.
* FP Function Optimizations:: Fast code or small code.
Pseudo-Random Numbers
* ISO Random:: @code{rand} and friends.
* BSD Random:: @code{random} and friends.
* SVID Random:: @code{drand48} and friends.
Arithmetic
* Floating Point Numbers:: Basic concepts. IEEE 754.
* Floating Point Classes:: The five kinds of floating-point number.
* Floating Point Errors:: When something goes wrong in a calculation.
* Rounding:: Controlling how results are rounded.
* Control Functions:: Saving and restoring the FPU's state.
* Arithmetic Functions:: Fundamental operations provided by the library.
* Complex Numbers:: The types. Writing complex constants.
* Operations on Complex:: Projection, conjugation, decomposition.
* Integer Division:: Integer division with guaranteed rounding.
* Parsing of Numbers:: Converting strings to numbers.
* System V Number Conversion:: An archaic way to convert numbers to strings.
Floating Point Errors
* FP Exceptions:: IEEE 754 math exceptions and how to detect them.
* Infinity and NaN:: Special values returned by calculations.
* Status bit operations:: Checking for exceptions after the fact.
* Math Error Reporting:: How the math functions report errors.
Arithmetic Functions
* Absolute Value:: Absolute values of integers and floats.
* Normalization Functions:: Extracting exponents and putting them back.
* Rounding Functions:: Rounding floats to integers.
* Remainder Functions:: Remainders on division, precisely defined.
* FP Bit Twiddling:: Sign bit adjustment. Adding epsilon.
* FP Comparison Functions:: Comparisons without risk of exceptions.
* Misc FP Arithmetic:: Max, min, positive difference, multiply-add.
Parsing of Numbers
* Parsing of Integers:: Functions for conversion of integer values.
* Parsing of Floats:: Functions for conversion of floating-point
values.
Date and Time
* Processor Time:: Measures processor time used by a program.
* Calendar Time:: Manipulation of ``real'' dates and times.
* Setting an Alarm:: Sending a signal after a specified time.
* Sleeping:: Waiting for a period of time.
* Resource Usage:: Measuring various resources used.
* Limits on Resources:: Specifying limits on resource usage.
* Priority:: Reading or setting process run priority.
Processor Time
* Basic CPU Time:: The @code{clock} function.
* Detailed CPU Time:: The @code{times} function.
Calendar Time
* Simple Calendar Time:: Facilities for manipulating calendar time.
* High-Resolution Calendar:: A time representation with greater precision.
* Broken-down Time:: Facilities for manipulating local time.
* Formatting Date and Time:: Converting times to strings.
* TZ Variable:: How users specify the time zone.
* Time Zone Functions:: Functions to examine or specify the time zone.
* Time Functions Example:: An example program showing use of some of
the time functions.
Non-Local Exits
* Intro: Non-Local Intro. When and how to use these facilities.
* Details: Non-Local Details. Functions for nonlocal exits.
* Non-Local Exits and Signals:: Portability issues.
Signal Handling
* Concepts of Signals:: Introduction to the signal facilities.
* Standard Signals:: Particular kinds of signals with
standard names and meanings.
* Signal Actions:: Specifying what happens when a
particular signal is delivered.
* Defining Handlers:: How to write a signal handler function.
* Interrupted Primitives:: Signal handlers affect use of @code{open},
@code{read}, @code{write} and other functions.
* Generating Signals:: How to send a signal to a process.
* Blocking Signals:: Making the system hold signals temporarily.
* Waiting for a Signal:: Suspending your program until a signal
arrives.
* Signal Stack:: Using a Separate Signal Stack.
* BSD Signal Handling:: Additional functions for backward
compatibility with BSD.
Concepts of Signals
* Kinds of Signals:: Some examples of what can cause a signal.
* Signal Generation:: Concepts of why and how signals occur.
* Delivery of Signal:: Concepts of what a signal does to the
process.
Standard Signals
* Program Error Signals:: Used to report serious program errors.
* Termination Signals:: Used to interrupt and/or terminate the
program.
* Alarm Signals:: Used to indicate expiration of timers.
* Asynchronous I/O Signals:: Used to indicate input is available.
* Job Control Signals:: Signals used to support job control.
* Operation Error Signals:: Used to report operational system errors.
* Miscellaneous Signals:: Miscellaneous Signals.
* Signal Messages:: Printing a message describing a signal.
Signal Actions
* Basic Signal Handling:: The simple @code{signal} function.
* Advanced Signal Handling:: The more powerful @code{sigaction} function.
* Signal and Sigaction:: How those two functions interact.
* Sigaction Function Example:: An example of using the sigaction function.
* Flags for Sigaction:: Specifying options for signal handling.
* Initial Signal Actions:: How programs inherit signal actions.
Defining Handlers
* Handler Returns:: Handlers that return normally, and what
this means.
* Termination in Handler:: How handler functions terminate a program.
* Longjmp in Handler:: Nonlocal transfer of control out of a
signal handler.
* Signals in Handler:: What happens when signals arrive while
the handler is already occupied.
* Merged Signals:: When a second signal arrives before the
first is handled.
* Nonreentrancy:: Do not call any functions unless you know they
are reentrant with respect to signals.
* Atomic Data Access:: A single handler can run in the middle of
reading or writing a single object.
Atomic Data Access
* Non-atomic Example:: A program illustrating interrupted access.
* Types: Atomic Types. Data types that guarantee no interruption.
* Usage: Atomic Usage. Proving that interruption is harmless.
Generating Signals
* Signaling Yourself:: A process can send a signal to itself.
* Signaling Another Process:: Send a signal to another process.
* Permission for kill:: Permission for using @code{kill}.
* Kill Example:: Using @code{kill} for Communication.
Blocking Signals
* Why Block:: The purpose of blocking signals.
* Signal Sets:: How to specify which signals to
block.
* Process Signal Mask:: Blocking delivery of signals to your
process during normal execution.
* Testing for Delivery:: Blocking to Test for Delivery of
a Signal.
* Blocking for Handler:: Blocking additional signals while a
handler is being run.
* Checking for Pending Signals:: Checking for Pending Signals
* Remembering a Signal:: How you can get almost the same
effect as blocking a signal, by
handling it and setting a flag
to be tested later.
Waiting for a Signal
* Using Pause:: The simple way, using @code{pause}.
* Pause Problems:: Why the simple way is often not very good.
* Sigsuspend:: Reliably waiting for a specific signal.
BSD Signal Handling
* BSD Handler:: BSD Function to Establish a Handler.
* Blocking in BSD:: BSD Functions for Blocking Signals.
Process Startup
* Program Arguments:: Parsing your program's command-line arguments.
* Environment Variables:: How to access parameters inherited from
a parent process.
* Program Termination:: How to cause a process to terminate and
return status information to its parent.
Program Arguments
* Argument Syntax:: By convention, options start with a hyphen.
* Parsing Program Arguments:: Ways to parse program options and arguments.
Parsing Program Arguments
* Getopt:: Parsing program options using @code{getopt}.
* Argp:: Parsing program options using @code{argp_parse}.
* Suboptions:: Some programs need more detailed options.
* Suboptions Example:: This shows how it could be done for @code{mount}.
Environment Variables
* Environment Access:: How to get and set the values of
environment variables.
* Standard Environment:: These environment variables have
standard interpretations.
Program Termination
* Normal Termination:: If a program calls @code{exit}, a
process terminates normally.
* Exit Status:: The @code{exit status} provides information
about why the process terminated.
* Cleanups on Exit:: A process can run its own cleanup
functions upon normal termination.
* Aborting a Program:: The @code{abort} function causes
abnormal program termination.
* Termination Internals:: What happens when a process terminates.
Processes
* Running a Command:: The easy way to run another program.
* Process Creation Concepts:: An overview of the hard way to do it.
* Process Identification:: How to get the process ID of a process.
* Creating a Process:: How to fork a child process.
* Executing a File:: How to make a process execute another program.
* Process Completion:: How to tell when a child process has completed.
* Process Completion Status:: How to interpret the status value
returned from a child process.
* BSD Wait Functions:: More functions, for backward compatibility.
* Process Creation Example:: A complete example program.
Job Control
* Concepts of Job Control:: Jobs can be controlled by a shell.
* Job Control is Optional:: Not all POSIX systems support job control.
* Controlling Terminal:: How a process gets its controlling terminal.
* Access to the Terminal:: How processes share the controlling terminal.
* Orphaned Process Groups:: Jobs left after the user logs out.
* Implementing a Shell:: What a shell must do to implement job control.
* Functions for Job Control:: Functions to control process groups.
Implementing a Shell
* Data Structures:: Introduction to the sample shell.
* Initializing the Shell:: What the shell must do to take
responsibility for job control.
* Launching Jobs:: Creating jobs to execute commands.
* Foreground and Background:: Putting a job in foreground of background.
* Stopped and Terminated Jobs:: Reporting job status.
* Continuing Stopped Jobs:: How to continue a stopped job in
the foreground or background.
* Missing Pieces:: Other parts of the shell.
Functions for Job Control
* Identifying the Terminal:: Determining the controlling terminal's name.
* Process Group Functions:: Functions for manipulating process groups.
* Terminal Access Functions:: Functions for controlling terminal access.
Name Service Switch
* NSS Basics:: What is this NSS good for.
* NSS Configuration File:: Configuring NSS.
* NSS Module Internals:: How does it work internally.
* Extending NSS:: What to do to add services or databases.
NSS Configuration File
* Services in the NSS configuration:: Service names in the NSS configuration.
* Actions in the NSS configuration:: React appropriately to the lookup result.
* Notes on NSS Configuration File:: Things to take care about while
configuring NSS.
NSS Module Internals
* NSS Module Names:: Construction of the interface function of
the NSS modules.
* NSS Modules Interface:: Programming interface in the NSS module
functions.
Extending NSS
* Adding another Service to NSS:: What is to do to add a new service.
* NSS Module Function Internals:: Guidelines for writing new NSS
service functions.
Users and Groups
* User and Group IDs:: Each user has a unique numeric ID;
likewise for groups.
* Process Persona:: The user IDs and group IDs of a process.
* Why Change Persona:: Why a program might need to change
its user and/or group IDs.
* How Change Persona:: Changing the user and group IDs.
* Reading Persona:: How to examine the user and group IDs.
* Setting User ID:: Functions for setting the user ID.
* Setting Groups:: Functions for setting the group IDs.
* Enable/Disable Setuid:: Turning setuid access on and off.
* Setuid Program Example:: The pertinent parts of one sample program.
* Tips for Setuid:: How to avoid granting unlimited access.
* Who Logged In:: Getting the name of the user who logged in,
or of the real user ID of the current process.
* User Accounting Database:: Keeping information about users and various
actions in databases.
* User Database:: Functions and data structures for
accessing the user database.
* Group Database:: Functions and data structures for
accessing the group database.
* Database Example:: Example program showing the use of database
inquiry functions.
* Netgroup Database:: Functions for accessing the netgroup database.
User Accounting Database
* Manipulating the Database:: Scanning and modifying the user
accounting database.
* XPG Functions:: A standardized way for doing the same thing.
* Logging In and Out:: Functions from BSD that modify the user
accounting database.
User Database
* User Data Structure:: What each user record contains.
* Lookup User:: How to look for a particular user.
* Scanning All Users:: Scanning the list of all users, one by one.
* Writing a User Entry:: How a program can rewrite a user's record.
Group Database
* Group Data Structure:: What each group record contains.
* Lookup Group:: How to look for a particular group.
* Scanning All Groups:: Scanning the list of all groups.
Netgroup Database
* Netgroup Data:: Data in the Netgroup database and where
it comes from.
* Lookup Netgroup:: How to look for a particular netgroup.
* Netgroup Membership:: How to test for netgroup membership.
System Information
* Host Identification:: Determining the name of the machine.
* Hardware/Software Type ID:: Determining the hardware type of the
machine and what operating system it is
running.
* Filesystem handling:: Which is mounted and/or available?
System Configuration
* General Limits:: Constants and functions that describe
various process-related limits that have
one uniform value for any given machine.
* System Options:: Optional POSIX features.
* Version Supported:: Version numbers of POSIX.1 and POSIX.2.
* Sysconf:: Getting specific configuration values
of general limits and system options.
* Minimums:: Minimum values for general limits.
* Limits for Files:: Size limitations that pertain to individual files.
These can vary between file systems
or even from file to file.
* Options for Files:: Optional features that some files may support.
* File Minimums:: Minimum values for file limits.
* Pathconf:: Getting the limit values for a particular file.
* Utility Limits:: Capacity limits of some POSIX.2 utility programs.
* Utility Minimums:: Minimum allowable values of those limits.
* String Parameters:: Getting the default search path.
Sysconf
* Sysconf Definition:: Detailed specifications of @code{sysconf}.
* Constants for Sysconf:: The list of parameters @code{sysconf} can read.
* Examples of Sysconf:: How to use @code{sysconf} and the parameter
macros properly together.
POSIX Threads
* Basic Thread Operations:: Creating, terminating, and waiting for threads.
* Thread Attributes:: Tuning thread scheduling.
* Cancellation:: Stopping a thread before it's done.
* Cleanup Handlers:: Deallocating resources when a thread is
cancelled.
* Mutexes:: One way to synchronize threads.
* Condition Variables:: Another way.
* POSIX Semaphores:: And a third way.
* Thread-Specific Data:: Variables with different values in
different threads.
* Threads and Signal Handling:: Why you should avoid mixing the two, and
how to do it if you must.
* Miscellaneous Thread Functions:: A grab bag of utility routines.
Language Features
* Consistency Checking:: Using @code{assert} to abort if
something ``impossible'' happens.
* Variadic Functions:: Defining functions with varying numbers
of args.
* Null Pointer Constant:: The macro @code{NULL}.
* Important Data Types:: Data types for object sizes.
* Data Type Measurements:: Parameters of data type representations.
Variadic Functions
* Why Variadic:: Reasons for making functions take
variable arguments.
* How Variadic:: How to define and call variadic functions.
* Variadic Example:: A complete example.
How Variadic
* Variadic Prototypes:: How to make a prototype for a function
with variable arguments.
* Receiving Arguments:: Steps you must follow to access the
optional argument values.
* How Many Arguments:: How to decide whether there are more arguments.
* Calling Variadics:: Things you need to know about calling
variable arguments functions.
* Argument Macros:: Detailed specification of the macros
for accessing variable arguments.
* Old Varargs:: The pre-ISO way of defining variadic functions.
Data Type Measurements
* Width of Type:: How many bits does an integer type hold?
* Range of Type:: What are the largest and smallest values
that an integer type can hold?
* Floating Type Macros:: Parameters that measure the floating point types.
* Structure Measurement:: Getting measurements on structure types.
Floating Type Macros
* Floating Point Concepts:: Definitions of terminology.
* Floating Point Parameters:: Details of specific macros.
* IEEE Floating Point:: The measurements for one common
representation.
Installation
* Configuring and compiling:: How to compile and test GNU libc.
* Running make install:: How to install it once you've got it compiled.
* Tools for Compilation:: You'll need these first.
* Supported Configurations:: What it runs on, what it doesn't.
* Linux:: Specific advice for Linux systems.
* Reporting Bugs:: So they'll get fixed.
Maintenance
* Source Layout:: How to add new functions or header files
to the GNU C library.
* Porting:: How to port the GNU C library to
a new machine or operating system.
Porting
* Hierarchy Conventions:: The layout of the @file{sysdeps} hierarchy.
* Porting to Unix:: Porting the library to an average
Unix-like system.
@end menu
|