Linux System Programming | O'Reilly Media

Linux System Programming Talking Directly to the Kernel and C Library By Robert Love
September 2007
Pages: 388

Index

[ Symbol ], [ A ], [ B ], [ C ], [ D ], [ E ], [ F ], [ G ], [ H ], [ I ], [ J ], [ K ], [ L ], [ M ], [ N ], [ O ], [ P ], [ R ], [ S ], [ T ], [ U ], [ V ], [ W ], [ X ], [ Y ], [ Z ],

Symbol[ Top ]
/ (forward slash), 11

A [ Top ]
ABIs (application binary interfaces), 4, 5
abort( ) function, 282
absolute pathnames, 11, 212
absolute time, 309
access control lists (ACLs), 18
ACLs (access control lists), 18
adjtime( ) function, 322
adjtimex( ) function, 322-324
aio interfaces, 112
alarm( ) function, 282, 330
alarm_handler( ) function, 331
alignment of data, 252
_ _alignof_ _ keyword, 346
alloca( ) function, 264
duplicating strings on the stack, 266
allocation, 243
anonymous memory mappings, 256-260
creating, 257
mapping /dev/zero, 259
ANSI C, 7
Anticipatory I/O Scheduler, 117
anti-lock braking system (ABS) as real-time system, 176
APIs (application programming interfaces), 4
append mode, write( ), 34
applications
time dependency and the system clock, 321
arrays, allocation of, 247
asctime( ) and asctime_r( ) functions, 320
asynchronous events, signals for (see signals)
asynchronous I/O, 112
asynchronous write operations, 111
atexit( ) function, 137
_ _attribute_ _ syntax, beautifying with preprocessor macros, 349
automatic variables, 264

B [ Top ]
background process groups, 154
batch scheduling policy, 180
bcmp( ) function, 270
bdflush threads, 61
big-oh notation, 163
binary compatibility, 5
binary files and text files, 66
block devices, 13
sectors, 14
blocking reads, 30
blocks, 15, 62
block size, 63
effects on performance, 63
break point, 255
brk( ) function, 256
broken links, 12
bss segment, 245
buddy memory allocation scheme, 256
buffer size, 64
buffered I/O (input/output), 62
associated file descriptors, obtaining, 77
block size, 63
effects on performance, 63
controlling the buffering, 77
errors and EOF, 76
opening files, 65
modes, 65
sample program, 72-74
standard I/O, 64
file pointers, 65
limitations, 81
streams
closing, 67
closing all, 67
flushing, 75
opening via file descriptors, 66
seeking a stream, 74
streams, reading from, 67-70
putting the character back, 68
reading an entire line, 68
reading arbitrary strings, 69
reading binary data, 70
reading one character at at time, 67
streams, writing to, 70-72
data alignment, 71
writing a single character, 71
writing a string, 72
writing binary data, 72
thread safety, 79-81
manual file locking, 80
unlocked stream operations, 81
user-buffered I/O, 62-64
buffer_head data structure, 61
buffers, 37, 61
dirty buffers, 60
_ _builtin_return_address keyword, 348

C [ Top ]
C compiler (see gcc)
C language, 7, 64
GNU C, 339
C library (libc), 4
cache effects of process migration, 173
calloc( ) function, 247
capabilities system, 18
CAP_IPC_LOCK, 276
CAP_KILL capability, 292
CAP_SYS_TIME, 318
case statement, 348
cd command, 216
character devices and character device files, 13
chdir( ) function, 215
child processes, 17, 127
memory inheritance and fork( ), 274
(see also processes)
chmod( ) function, 200
chown( ) function, 201
clearerr( ) function, 76
clock_getres( ) function, 314
clock_gettime( ) function, 316
clockid_t type, 313
clock_nanosleep( ) function, 327
clock_settime( ) function, 319
close( ) function, 41
code examples, permissions, xv
common file model, 58
Complete Fair Queuing (CFQ) I/O Scheduler, 118
congestion avoidance, 61
const keyword, 341
controlling terminals, 154
cooperative multitasking, 163
yielding, 163, 166-169
legitimate uses, 167
Linux version 2.6, changes in, 168
copy-on-write (COW), 134, 244
CPU_SETSIZE, 174
creat( ) function, 28
critical regions, 79, 297
ctime( ) function and ctime_r( ) functions, 320
current time, getting, 315-318
microsecond resolution, 316
nanosecond resolution, 316
current time, setting, 318, 319
current working directory (cwd), 11, 213-217
changing, 215-217
obtaining, 213-215

D [ Top ]
daemon( ) function, 160
daemons, 159-161
dangling symlinks, 225
data alignment, 71
data segment, 245
data segment management, 255
Deadline I/O Scheduler, 116
defined keys, 204
demand paging, 273
determinism, 187-189
/dev/zero, 259
device nodes, 231-232
major and minor numbers, 231
random number generators, 232
special nodes, 231
devices, 13
/dev/zero, 259
out-of-band communication, 233
difftime( ) function, 321
direct I/O, 40
directories, 11, 212-223
creating, 218
current working directory (cwd), 213-217
changing, 215-217
obtaining, 213-215
directory entries, 212
directory entry (dentry), 11
directory stream, 220
closing, 221
reading from, 221
links, 212, 223-228
names, legal characters for, 212
names, length of, 212
reading contents of, 220-223
system calls for, 222
removing, 219
subdirectories, 212
dirfd( ) function, 220
dirty buffers, 60
dirty_expire_centiseconds, 37
disk addressing, 114
dnotify function, 235
dynamic memory allocation, 245-255
alignment, 252-255
alignment of nonstandard and complex types, 254
allocating aligned memory, 252
pointers, 255
allocating arrays, 247
freeing dynamic memory, 250-252
resizing allocations, 249

E [ Top ]
edge-triggered events, 94
effective gid, 17
effective user ID (uid), 17, 150
eject command program, 233
elevator algorithms, 116
end-of-file (see EOF)
entropy pool, 232
EOF (end-of-file), 30
errors and, 76
epoch, 309
epoll facility, 89
epoll interface, 57
epoll_create( ) function, 89
epoll_ctl( ) function, 90-92
epoll_wait( ) function, 93
errno, 19-22
error descriptors, 20
error handling, 19-22
errors and EOF, 76
event poll interface, 89-94
controlling epoll, 90-92
creating an epoll instance, 89
edge-triggered versus level-triggered events, 94
waiting for events, 93
exec family of functions, 129-132
error values, 131
execl( ) function, 129-130
execute permissions, 18
exit( ) and _exit( ) functions, 136
extended attributes, 203
keys and values, 204
listing, 209
namespaces, 205
operations, 206
removal, 210
retrieval, 206
security namespace, 206
setting, 208
system namespace, 205
trusted namespace, 206
user namespace, 206
external fragmentation, 256

F [ Top ]
fchdir( ) function, 215
fchmod( ) function, 200
fchown( ) function, 202
fclose( ) function, 67
fcloseall( ) function, 67
fd (see file descriptors)
fdatasync( ) function, 37
return values and error codes, 38
feof( ) function, 76
ferror( ) function, 76
fflush( ) function, 75
fgetc( ) function, 67, 69
fgetpos( ) function, 75
fgets( ) function, 68
fgetxattr( ) function, 207
FIFO (first in, first out) class, 179
FIFOs, 13
file descriptors, 9, 23
streams, opening via, 66
file I/O (input/output), 23-61
advice, 108-111
advantages, 110
posix_fadvise( ) function, 108
closing files, 41
direct I/O, 40
event poll interface (see event poll interface)
I/O schedulers (see I/O schedulers)
kernel internals, 57-61
page cache, 59
page writeback, 60
virtual filesystem, 58
linear output, 84
lseek( ), 42-44
error values, 44
limitations, 44
seeking past the end of a file, 43
memory mapped I/O (see memory mapped I/O)
multiplexed I/O, 47-57
poll( ) function, 53-56
poll( ) versus select( ), 57
ppoll( ) function, 56
pselect( ) function, 52
select( ) function, 48-53
opening files, 24-29
creat( ) function, 28
open( ) function, 24-26
owners of new files, 26
permissions of new files, 27
return values and error codes, 29
positional reads and writes, 44
error values, 45
readahead( ) function, 110
reading files, 29-33
additional error values, 32
nonblocking reads, 32
reading all the bytes, 31
return values, 30
size limits on read( ), 33
scatter/gather I/O (see scatter/gather I/O)
synchronized I/O, 37-40
fsync( ) and fdatasync( ), 37
O_DSYNC and O_RSYNC flags, 40
O_SYNC flag, 39
sync( ) function, 39
truncating files, 45
write( ), 33-37
additional error codes, 35
append mode, 34
behavior of write( ), 36
nonblocking writes, 35
partial writes, 34
size limits on, 36
file pointers, 65
file table, 23
FILE typedef, 65
fileno( ) function, 77
files, 9-15
access, modification, and change times, 198
closing files, 41
copying, 228
deleting, 12
device nodes, 231-232
major and minor numbers, 231
random number generators, 232
special nodes, 231
directories (see directories)
extended attributes (see extended attributes)
file events, monitoring, 234-242
inotify interface, 234
watches, 236-242
file I/O (see file I/O)
file ownership, 26
file permissions, 27
file position or file offset, 9
file truncation, 45
filenames and inodes, 10
inodes, 196
length, 10
links, 11, 223-228
metadata, 196
functions for obtaining, 196
MIME types, storage, 205
mode, legal values for, 200
moving, 229
effects of moving to and from different types of files, 230
names, legal characters for, 212
names, length of, 212
ownership, 201
permissions, 199
mode argument, 27
regular files, 9
special files, 13
usage count, 223
filesystem gid, 17
filesystem uid, 17
filesystems, 14
blocks, 15
filesystem-agnosticism, 204
links and, 223
mounting and unmounting, 14
supported in Linux, 14
flistxattr( ) function, 210
flockfile( ) function, 80
fopen( ) function, 65
foreground process group, 154
fork( ) function, 17, 132-136, 290
forward slash (/), 11
fputc( ) function, 71
fputs( ) function, 72
fremovexattr( ) function, 211
fseek( ) function, 74
fsetpos( ) function, 74
fsetxattr( ) function, 208
fstat( ) function, 197
fsync( ) function, 37, 76
return values and error codes, 38
ftell( ) function, 75
ftruncate( ) function, 46
ftrylockfile( ) function, 80
full device, 232
fully qualified pathnames, 11
functions
constant functions, 341
inline functions, 340
suppressing inlining, 340
marking as deprecated, 343
marking as unused, 343
marking as used, 343
memory allocation functions, 342
nonreturning functions, 342
pure functions, 341
funlockfile( ) function, 80
fwrite( ) function, 72

G [ Top ]
gcc (binary), 4
supported standards, 8
GCC (GNU Compiler Collection), 4
C language extensions, 339-350
branch annotation, 345
case ranges, 348
constant functions, 341
deprecated functions, marking, 343
expression types, getting, 346
forcing functions to check return values, 342
functions or parameters, marking as unused, 343
function's return address, obtaining, 348
global variables, placing in a register, 345
GNU C, 339
inline functions, 340
inline functions, suppressing, 340
member offset within a structure, 347
memory allocation functions, 342
nonreturning functions, 342
packing structures, 343
portability, improving, 349
pure functions, 341
type alignment, getting, 346
used functions, marking, 343
variable alignment, increasing, 344
void and pointer arithmetic, 349
get_current_dir_name( ) function, 214
getcwd( ) function, 213, 216
getdents( ) function, 222
getitimer( ) function, 332
getpagesize( ) function, 98
getpgid( ) function, 158
getpgrp( ) function, 158
getpid( ) function, 128
getpriority( ) function, 171
getrlimit( ) functionl, 190
gets( ) function, 81
getsid( ) function, 156
gettimeofday( ) function, 316
getwd( ) function, 214
getxattr( ) function, 207
ghosts, 149
gid (group ID), 17
glibc (GNU libc), 4
memory allocation, 256
global register variables, 345
gmtime( ) and gmtime_r( ) functions, 320
GNU C, 8, 339
GNU Compiler Collection (see gcc)
GNU libc (glibc), 4
group ID (gid), 17
groups, 17
ownership of processes, 127
primary or logon groups, 17
GUI file managers, MIME type sniffing behaviors, 205

H [ Top ]
hard affinity, 173
hard links, 12, 223, 224
hard real-time systems, 176
hard resource limit, 190
hardware clocks, 310
headers, 19
heap, 245
hwclock command, 310

I [ Top ]
idle processes, 126
idle scheduling policy, 180
IEEE (Institute of Electrical and Electronics Engineers), 6
init process, 17, 126
inline functions, 340
suppressing inlining, 340
inline keyword, 340
inode number, obtaining, 196
inodes, 10, 196
link count, 12
inotify events, 238-240
advanced events, 239
linking together move events, 240
reading, 238
inotify interface, 234
initializing, 235
inotify_add_watch( ) function, 236, 238
inotify_event structure, 238
inotify_init( ) function, 235
Institute of Electrical and Electronics Engineers (IEEE), 6
internal fragmentation, 256
International Organization for Standardization (ISO), 7
interprocess communications (IPCs), 13, 19
interval timers, 331
invalid page, 244
I/O (input/output)
asynchronous I/O, 112
buffered I/O (see buffered I/O)
file I/O (see file I/O)
I/O priorities, 172
I/O schedulers (see I/O schedulers)
I/O wait time, 40
I/O-bound processes, 164
system calls and, 77
I/O schedulers, 114-125
disk addressing, 114
lifecycle, 115
merging and sorting, 115
performance optimization, 119-125
reads, 116-119
Anticipatory I/O Scheduler, 117
Complete Fair Queuing (CFQ) I/O Scheduler, 118
Deadline I/O Scheduler, 116
Noop I/O Scheduler, 119
scheduling in user space, 120
sorting by inode, 121
sorting by path, 120
sorting by physical block, 122
selection and configuration, 119
ioctl( ) function, 233
IOV_MAX, 85
IPCs (interprocess communications), 13
ISO (International Organization for Standardization), 7
itimerval structure, 332

J [ Top ]
jiffies counter, 309
jitter, 177
job control, 154

K [ Top ]
kernel
file mapping interface (see memory mapped I/O)
I/O (input/output), implementation of, 57-61
page cache, 59
page writeback, 60
virtual filesystem, 58
I/O schedulers (see I/O schedulers), 114
kernel buffering contrasted with user-buffered I/O, 62
mapping advice and, 106
readahead, 107
system timer, 309
time measurement, 308
usage of file descriptors, 23
user-space applications, communication with, 3
kernel time, 40
keys, 204
kill( ) function, 284, 291, 307
signal for, 303
kill command, 281

L [ Top ]
latency, 177
lchown( ) function, 201
level-triggered events, 94
lgetxattr( ) function, 207
libc (C library), 4
likely( ) wrapper, 345
linear I/O, 84
link( ) function, 224
links, 11, 212, 223-228
broken links, 12
hard links, 12, 224
link count, 12
symbolic links, 12, 225
unlinking, 227
Linus Elevator, 116
Linux, 1
C standards and, 7
forward compatibility, 8
Linux Standard Base (LSB), 8
Unix compared to, 1
Linux Foundation, 8
Linux system interface, xiii
listxattr( ) function, 209
llistxattr( ) function, 210
load balancing, 173
locality of reference, 59
localtime( ) and localtime_r( ) functions, 321
login, 17
login shell, 17, 154
logon group, 17
lremovexattr( ) function, 211
ls command, 196
LSB (Linux Standard Base), 8
lseek( ) function, 42-44
error values, 44
limitations, 44
seeking past the end of a file, 43
lsetxattr( ) function, 208
lstat( ) function, 197

M [ Top ]
machine register, 3
madvise( ) function, 106-108
return values and error codes, 108
make, time dependency of, 321
mallinfo( ) function, 263
malloc( ) function, 246
xmalloc( ) wrapper for, 247
malloc0( ) function, 248
MALLOC_CHECK_ environment variable, 263
malloc_usable_size( ) and malloc_trim( ) functions, 262
mallopt( ) function, 260
parameters, 261
mapped files, 245
mappings, 245
maximum buffer age, 37
memchr( ) function, 272
memcmp( ) function, 270
memfrob( ) function, 272
memmem( ) function, 272
memmove( ) function, 271
memory addressing and data alignment, 71
memory allocation, 243
advanced memory allocation, 260-263
malloc_usable_size( ) and malloc_trim( ) functions, 262
mallopt( ) function, 260
choosing a mechanism, 268
debugging, 263
MALLOC_CHECK_, 263
obtaining statistics, 263
dynamic memory, allocating, 245-255
alignment, 252-255
allocating arrays, 247
freeing dynamic memory, 250-252
resizing allocations, 249
opportunistic allocation, 277
overcommitment and OOM, 277
stack-based allocations, 264-268
duplicating strings on the stack, 266
variable-length arrays, 267
unlocking memory, 275
memory management, 243
anonymous memory mappings, 256-260
creating, 257
mapping /dev/zero, 259
data segment, managing, 255
locking memory, 273-277
demand paging, 273
locking all of an address space, 275
locking limits, 276
locking part of an address space, 274
manipulating memory, 269-273
comparing bytes, 270
frobnicating bytes, 272
moving bytes, 271
searching bytes, 272
setting bytes, 269
memory management units, 15
process address space, 243-245
memory regions, 245
pages and paging, 243
sharing and copy-on-write, 244
memory mapped I/O, 95-108
changing the protection of a mapping, 104
giving advice, 106-108
mmap( ) function, 95-99, 100
advantages, 101
disadvantages, 102
page size, 97-98
munmap( ) function, 99
resizing a mapping, 102
SIGBUS and SIGSEGV signals, 99
synchronizing a file with a mapping, 104
memrchr( ) function, 272
memset( ) function, 269
merging (I/O schedulers), 115
metadata, 196
migration of processes, costs, 173
MIME types, storage, 205
mincore( ) function, 276
mkdir( ) function, 218, 229
mktime( ) function, 320
mlock( ) function, 274
mlockall( ) function, 275
mmap( ) function, 95-99, 258
advantages, 101
disadvantages, 102
example, 100
page size, 97-98
return values and erro codes, 99
mode argument, 27, 65
monotonic time, 308
mount points, 14
mounting, 14
mprotect( ) function, 104
mremap( ) function, 102
return values and error codes, 103
msync( ) function, 105
return values and error codes, 105
multiplexed I/O, 47-57
multitasking, 163
multithreaded programming, 166
munmap( ) function, 99, 258

N [ Top ]
named pipes, 13
namespaces, 14
per-process namespaces, 15
nanosleep( ) function, 326
natural alignment, 71, 252
network filesystems, 14
nice( ) function, 170
nice values, 169
noinline keyword, 340
nonblocking I/O, 32
nonblocking writes, 35
Noop I/O Scheduler, 119
noreturn keyword, 342
null device, 231

O [ Top ]
O(1) process scheduler, 163
O_DSYNC flag, 40
offset, 74
offsetof( ) macro, 347
off_t type, 44
on_exit function, 138
OOM (out of memory) conditions, 278
open( ) function, 24-26
O_DSYNC andO_RSYNC flags, 40
O_SYNC flag, 39
Open Software Foundation (OSF), 7
opendir( ) function, 220
operational deadlines, 176
latency and jitter, 177
opportunistic allocation, 277
origin argument, lseek( ), 42
O_RSYNC flag, 40
OSF (Open Software Foundation), 7
O_SYNC flag, 39
out of memory (OOM) conditions, 278
out-of-band communication, 233
overcommitment, 277

P [ Top ]
packed attribute, 343
pages, 97-98, 243
page cache, 59
page cache readahead, 60
page size, 15
page writeback, 60
PAGE_SIZE macro, 98
parameter passing, 3
parameters, marking as unused, 343
parent directories, 212
parent process, 17
parent processes, 127
(see also processes)
partial writes, 34
path, 11
pathnames, 11, 212
pause( ) function, 287
pdflush threads, 61
pending signals, 297
permission bits, 18
per-process namespaces, 15
perror( ) function, 21
pgid (process group ID), 154
pid (process ID), 16, 126
allocation, 127
pid_t type, 128
pointers, 255
poll( ) function, 53-56
disadvantages, 89
example, 55
return values and error codes, 55
select( ), versus, 57
Portable Operating System Interface (see POSIX)
POSIX, 6
history, 6
protection bits and architecture, 96
POSIX clocks, 313-315
clockid_t type, 313
time source resolution, 314
POSIX clocks-based timers, 333-338
arming a timer, 335
creating a timer, 333-335
deleting a timer, 338
obtaining timer expiration, 336
obtaining timer overrun, 337
_POSIX_SAVED_IDS macro, 153
posix_fadvise( ) function, 108
return values and error codes, 110
ppoll( ) function, 56
pread( ) function, 44
preemptive multitasking, 163
preemptive scheduling, 165
primary group, 17
process address space, 243-245
mapped files, 245
memory regions, 245
pages and paging, 243
sharing and copy-on-write, 244
process ID (pid), 16
process time, 308
process tree, 17
processes, 15-17, 126
accesses, 18
background process groups, 154
child and parent processes, 127
child processes, waiting for, 139-149
BSD wait3( ) and wait4( ) functions, 145
status pointer macros, 140
wait( ) function, 139
waitid( ) function, 143
waitpid( ) function, 142
copy-on-write (COW), 134
daemons, 159-161
doctrine of least-privileged rights, 150
exec family of functions, 129-132
file descriptors and, 23
foreground process group, 154
fork( ) function, 132-136
hierarchy, 127
initialization processes, 126
I/O-bound processes, 164
launching and waiting for new processes, 147
migration costs, 173
multitasking, 163
yielding, 166-169
new processes, running, 129
obsolete process group functions, 158
ownership, 127
prioritization (see scheduler, prioritization)
process group, 128
process group system calls, 157
process groups, 154-155
process group ID (pgid), 154
process hierarchy, 16
process ID (pid), 126
allocation, 127
process IDs and parent process IDs, obtaining, 128
processor-bound prccesses, 164
reparenting, 149
resource limits, 190-195
default hard and soft limits, 193
Linux, resource limits provided by, 191-193
setting and retrieving limits, 194
soft and hard limits, 190
runlist, 162
runnable processes, 162
scheduler (see schedulers)
sessions, 154-157
terminating, 136-139
atexit( ) function, 137
by signal, 137
classic method, 137
exit( ) and _exit( ) functions, 136
kill by kernel, 137
on_exit( ) function, 138
SIGCHILD, 139
threads, 166
timeslices, 162, 164
users and groups, 149-154
changing IDs, BSD methods, 152
changing IDs, HP-UX methods, 152
obtaining user and group IDs, 154
preferred user/group ID manipulations, 153
real, effective, and saved user and group IDs, 150
real, effective user or group IDs, changing, 151
real or saved user and group IDs, changing, 151
support for saved user IDs, 153
vfork( ) function, 135
zombies, 17, 149
waiting on zombie processes, 139
(see also child processes; parent processes)
(see also real-time systems)
processor affinity, 172-176
sched_getaffinity( ) and sched_setaffinity functions, 173-176
programming
multithreaded programming, 166
programming concepts, 9-22
error handling, 19-22
files, 9-15
filesystems and namespaces, 14
headers, 19
interprocess communication, 19
permissions, 18
processes, 15-17
signals, 19
users and groups, 17
programs
critical regions, 297
protection flags and architecture, 96
PROT_READ and PROT_EXEC flags, 96
pselect( ) function, 52
psignal( ) function,, 290
pthreads API, 166
pure functions, 341
pure keyword, 341
pwrite( ) function, 45

R [ Top ]
raise( ) function, 292
signal for, 303
random number generators, 232
read( ) function, 29-33
additional error values, 32
nonblocking reads, 32
positional reads, 44
error values, 45
reading all the bytes, 31
return values, 30
size limits, 33
read FIFO queue, 116
read latency, 116
read permissions, 18
readahead, 60, 107
readahead( ) function, 110
return values and error codes, 110
readdir( ) function, 221, 222
readv( ) function, 84
implementation, 88
return values, 85
real gid, 17
real time, 308
real uid, 17
real user ID, 150
realloc( ) function, 249
real-time systems, 176-189
determinism, 187-189
CPU affinity and real-time processes, 188
prefaulting data and locking memory, 187
latency, jitter, and deadlines, 177
real-time processes, precautions with, 186
sched_rr_get_interval, 185
scheduling parameters, setting, 182-185
range of valid priorities, determining, 184-185
scheduling policy and priorities, 178-182
batch scheduling policy, 180
FIFO class, 179
normal policy, 180
RR (round-robin) class, 179
setting, 180-182
soft versus hard real-time systems, 176
support in Linux, 178
(see also processes; schedulers)
records, 9
reentrancy, 293
guaranteed-reentrant functions, 294
regular files, 9
relative pathnames, 11, 212
relative time format, 309
remove( ) function, 228
removexattr( ) function, 211
rename( ) function, 229
reparenting, 17
reparenting of processes, 149
resource limits of processes, 190-195
default hard and soft limits, 193
Linux, resource limits provided by, 191-193
setting and retrieving limits, 194
soft and hard limits, 190
rewind( ) function, 74
rlimit structure, 190
RLIMIT_CPU, 190
rmdir( ) function, 219
root directory, 11, 212
root filesystem, 14
root (root user), 17
round-robin (RR) class, 179
run list, 162
runnable processes, 162

S [ Top ]
saved group ID (gid), 17
saved user ID (uid), 17, 151
sbrk( ) function, 256
scatter/gather I/O, 84-89
advantages, 84
readv( ) and writev( ) functions, 84
implementation, 88
return values, 85
SCHED_BATCH, 180
sched_getaffinity( ) and sched_setaffinity functions, 173-176
sched_getparam( ) and sched_setparam( ) functions, 182-185
error codes, 183
sched_getscheduler( ) and sched_setscheduler( ) functions, 180-182
SCHED_OTHER, 180
SCHED_RR, 179
sched_rr_get_interval, 185
error codes, 186
schedulers, 162-166
load balancing, 173
multitasking, 163
O(1) process scheduler, 163
preemptive scheduling, 165
process prioritization, 169-172
getpriority( ) and setpriority( ) functions, 171
I/O priorities, 172
nice( ) function, 170
processor affinity, 172-176
sched_getaffinity( ) and sched_setaffinity functions, 173-176
sched_rr_get_interval, 185
scheduling parameters, setting, 182-185
range of valid priorities, determining, 184-185
scheduling policy, 178-182
batch scheduling policy, 180
FIFO class, 179
normal policy, 180
RR (round-robin) class, 179
setting, 180-182
(see also processes; real-time systems)
sched_yield( ) function, 166
legitimate uses, 167
Linux version 2.6, changes in, 168
sectors, 14
security namespace, 206
segmentation violations, signal for, 284
segments, 245
select( ) function, 48-53
disadvantages, 89
poll( ), versus, 57
use for sleeping, 329
sequential locality, 60
sessions, 154-157
session system calls, 156
setegid( ) function, 152
seteuid( ) function, 152, 153
setitimer( ) function, 282, 284, 332
setpgid( ) function, 157
setpgrp( ) function, 158
setresuid( ) function, 153
setreuid( ) function, 152
setrlimit( ) function, 190
setsid( ) function, 156
setsize parameter, 174
settimeofday( ) function, 318
setuid( ) function, 151, 153
setxattr( ) function, 208
si_code field, 302
values valid for SIGBUS, 303
sigaction( ) function, 298-300
sigaddset( ) function, 296
sigandset( ) function, 296
SIGBUS signal, 99
SIGCHILD, 139
SIGCONT signal, 292
sigdelset( ) function, 296
sigemptyset( ) function, 296
sigfillset( ) function, 296
SIGHUP, 154
siginfo_t structure, 300-302
SIGINT, 154
sigisemptyset( ) function, 296
sigismember( ) function, 296
signal( ) and sigaction( ) functions, 139
signal( ) function, 286, 307
signals, 19, 279-286
blocking signals, 296-298
retrieving pending signals, 297
waiting for a set of signals, 298
concepts, 280
identifiers, 280
critical regions and, 297
human-readable versus integer values, 281
Linux, supported by, 281-286
listing with kill -l command, 281
payloads, sending signals with, 305
example, 306
reentrancy, 293
guaranteed-reentrant functions, 294
sending, 291-293
examples, 292
permissions, 292
to a process group, 293
to yourself, 292
SIGINT and SIGTERM, 280
SIGKILL and SIGSTOP, 280
signal management, 286-291, 298-305
examples, 287
execution and inheritance, 289
mapping signal numbers to strings, 290
si_code field, 302-305
sigaction( ) function, 298-300
siginfo_t structure, 300-302
waiting for signals, 287
signal masks, 297
signal sets, 295
signal-safety, 294
sigorset( ) function, 296
sigpending( ) function, 298
sigprocmask( ) function, 297
sigqueue( ) function, 305
SIGSEGV signal, 99
sigsuspend( ) function, 298
Single Unix Specification (see SUS)
sleep( ) function, 324
sleeping, 324-330
sockets, 13
soft affinity, 173
soft links, 225
soft real-time systems, 176
soft resource limits, 190
software clocks, 309
sorting (I/O schedulers), 115
source compatibility, 5
special files, 13
stack, 245
duplicating strings on, 266
stack-based memory allocations, 264-268
strings, duplicating, 266
variable-length arrays, 267
standard error (stderr), 21
standard I/O, 64
file pointers, 65
limitations, 81
standard I/O library, 64
standards, 6
as dealt with in this book, 8
stat( ) function, 197
stat family, 196-199
stat structure, 197
fields, 197-199
static priority, 178
status pointer, 140
stderr (standard error), 21
stdin, stdout, and stderr file descriptors, 23
stdio, 64
stime( ) function, 318
strdup( ), strdupa( ), and strndupa( ) functions, 266
streams, 65
associated file descriptors, obtaining for, 77
closing, 67
closing all, 67
file descriptors, opening via, 66
flushing, 75
reading from, 67-70
putting the character back, 68
reading an entire line, 68
reading arbitrary strings, 69
reading binary data, 70
reading one character at at time, 67
seeking a stream, 74
obtaining current stream position, 75
writing to, 70-72
data alignment, 71
writing a single character, 71
writing a string, 72
writing binary data, 72
(see also buffered I/O)
strerror( ) function, 21
strerror_r( ) function, 21
strsignal( ) function, 290
subdirectories, 212
supplemental groups, 17
SUS (Single Unix Specification), 6
history, 6
standards UNIX 95, UNIX 98, and UNIX 03, 7
symbolic links (symlinks), 12, 223, 225
symlink( ) function, 226
symmetric multiprocessing, 172
sync( ) function, 39
synchronicity of write operations, 112
synchronization, 39
synchronized operations, 111
synchronous write operations, 111
sysconf( ) function, 98
sys_siglist, 290
system calls (syscalls), 3
I/O calls and, 77
system clock, tuning, 321-324
system namespace, 205
system programming, xi, 1-4
C compiler, 4
C library (libc), 4
functions
parameter passing, 3
programming concepts (see programming concepts)
standards, 6
system calls, 3
invoking, 3
system software, xi, 1
system timer, 309
system timer frequency, 309

T [ Top ]
temporal locality, 59
text files and binary files, 66
text segment, 245
The C Programming Language, xi
The Open Group, 6
thread-based asynchronous I/O, 113
threads, 79, 166
pthreads API, 166
thread safety, 79-81
manual file locking, 80
unlocked stream operations, 81
thread-safety, 79
tick or jiffy, 309
time, 308-310
C language conversion functions, 320-321
current time, getting, 315-318
microsecond resolution, 316
nanosecond resolution, 316
current time, setting, 318
clock_settime( ) function, 319
data structures, 310-313
clock_t type, 313
timespec (nanosecond precision), 311
time_t, 310
time_t and leap years, 315
timeval (microsecond precision), 311
tm structure for broken-down time representation, 312
delta, 322
epoch measurement, 309
kernel, measurement by, 308
measurement formats, 309
POSIX clocks, 313-315
clockid_t type, 313
time source resolution, 314
process time, getting, 317
sleeping, 324-330
alternatives to, 330
microsecond precision, 325
nanosecond precision, 326-329
select( ) function for portability, 329
timer overruns, 329
system clock, tuning, 321-324
timers, 330-338
alarms, 330
interval timers, 331-333
POSIX clocks-based timers, 333-338
time( ) function, 315
timer_create( ) function, 334
timer_delete( ) function, 338
timer_getoverrun( ) function, 337
timer_gettime( ) function, 336
timer_settime( ) function, 335
times( ) function, 317
timeslices, 162, 164
time_t type, 321
toolchain, 6
truncate( ) function, 46
truncation, 10
trusted namespace, 206
typeof( ) keyword, 346

U [ Top ]
uid (user ID), 17
umask, 218
undefined keys, 204
Universal Time, Coordinated (UTC), 309
Unix, 1
Unix text editors, xi
unlikely( ) wrapper, 345
unlink( ) function, 227
unlinking, 12
unmounting, 14
unused attribute, 343
user ID (uid), 17
user namespace, 206
user time, 40, 317
user-buffered I/O, 62-64
user-buffered I/O (input/output)
file descriptors, usage of, 23
usernames, 17
users, 17
ownership of processes, 127
user-space applications, communication with kernel, 3
usleep( ) function, 325
UTC (Universal Time, Coordinated), 309

V [ Top ]
valid page, 244
variable-length arrays (VLAs), 267
variadic functions, 129
vectored I/O, 84, 86
vectors, 85
vfork( ) function, 135
VFS (see virtual filesystems)
virtual address space, 243
virtual file switch, 58
virtual filesystems (VFS), 14, 58

W [ Top ]
wait( ) function, 139
waitid( ) function, 143
waiting on zombie processes, 139
waitpid( ) function, 142
wall time, 308
warn_unused_result attribute, 342
watches, 236-242
adding watches, 236
advanced options, 240
inotify events, 238-240
advanced events, 239
linking together move events, 240
reading, 238
watch masks, 236
whence, 74
word size, 44
-Wpointer-arith option, 349
write( ) function, 33-37
additional error codes, 35
append mode, 34
behavior of write( ), 36
nonblocking writes, 35
partial writes, 34
positional writes, 44
error values, 45
size limits on, 36
write FIFO queue, 116
write ordering, 36
write permissions, 18
writebacks, 36
writes-starving-reads problem, 116
writev( ) function, 85
example, 86
implementation, 88
return values, 85

X [ Top ]
X/Open, 7
xattrs (see extended attributes)
xmalloc( ) wrapper, 247

Y [ Top ]
yielding, 163, 166-169
legitimate uses, 167
Linux version 2.6, changes in, 168

Z [ Top ]
zero device, 232
zombies, 17, 149
waiting on zombie processes, 139

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