sys_calls

/usr/include/asm/unistd.h (sys/syscall.h)
the system call numbers:

sys_call name	sys_call num.(hex)
restart_syscall	0
_exit	1
fork	2
read	3
write	4
open	5
close	6
waitpid	7
create	8
link	9
unlink	a
execve	b
chdir	c
time	d
mknod	e
chmod	f
lchown	10
break	11
oldstat	12
lseek	13
getpid	14
mount	15
oldumount	16
setuid	17
getuid	18
stime	19
ptrace	1a
alarm	1b
oldfstat	1c
pause	1d
utime	1e
stty	1f
gtty	20
access	21
nice	22
ftime	23
sync	24
kill	25
rename	26
mkdir	27
rmdir	28
dup	29
pipe	2a
times	2b
prof	2c
brk	2d
setgid	2e
getgid	2f
signal	30
geteuid	31
getegid	32
acct	33
umount2	34
lock	35
ioctl	36
fcntl	37
mpx	38
setpgid	39
ulimit	3a
oldolduname	3b
umask	3c
chroot	3d
ustat	3e
dup2	3f
getppid	40
getpgrp	41
setsid	42
sigaction	43
sgetmask	44
ssetmask	45
setreuid	46
setregid	47
sigsuspend	48
sigpending	49
sethostname	4a
setrlimit	4b
getrlimit	4c /* Back compatible 2Gig limited rlimit */
getrusage	4d
gettimeofday	4e
settimeofday	4f
getgroups	50
setgroups	51
select	52
symlink	53
oldlstat	54
readlink	55
uselib	56
swapon	57
reboot	58
readdir	59
mmap	5a
munmap	5b
truncate	5c
ftruncate	5d
fchmod	5e
fchown	5f
getpriority	60
setpriority	61
profil	62
statfs	63
fstatfs	64
ioperm	65
socketcall	66
syslog	67
settimer	68
gettimer	69
stat	6a
lstat	6b
fstat	6c
olduname	6d
iopl	6e
vhangup	6f
idle	70
vm86old	71
wait4	72
swapoff	73
sysinfo	74
ipc	75
fsync	76
sigreturn	77
clone	78
setdomainname	79
uname	7a
modify_ldt	7b
adjtimex	7c
mprotect	7d
sigprocmask	7e
create_module	7f
init_module	80
delete_module	81
get_kernel_syms	82
quotactl	83
getpgid	84
fchdir	85
dbflush	86
sysfs	87
personality	88
afs_syscall	89 /* Syscall for Andrew File System */
setfsuid	8a
setfsgid	8b
_llseek	8c
getdents	8d
_newselect	8e
flock	8f
msync	90
readv	91
writev	92
getsid	93
fdatasync	94
_sysctl	95
mlock	96
munlock	97
mlockall	98
munlockall	99
sched_setparam	9a
sched_getparam	9b
sched_setscheduler	9c
sched_getscheduler	9d
sched_yield	9e
sched_get_priority_max	9f
sched_set_priority_min	a0
sched_rr_get_interval	a1
nanosleep	a2
mremap	a3
setresuid	a4
getresuid	a5
vm86	a6
query_module	a7
poll	a8
nfsservctl	a9
setresgid	aa
getresgid	ab
prctl	ac
rt_sigreturn	ad
rt_sigaction	ae
rt_sigprocmask	af
rt_sigpending	b0
rt_sigtimedwait	b1
rt_sigqueueinfo	b2
rt_sigsuspend	b3
pread64	b4
pwrite64	b5
chown	b6
getcwd	b7
capget	b8
capset	b9
sigaltstack	ba
sendfile	bb
getpmsg	bc /* some people actually want streams */
putpmsg	bd /* some people actually want streams */
vfork	be
ugetrlimit	bf /* SuS compliant getrlimit */
mmap2	c0
truncate64	c1
ftruncate64	c3
tkill	ee
io_setup	f5
io_destory	f6
io_getevents	f7
io_submit	f8
io_cancel	f9
exit_group	fc
timer_create	103
timer_settime	104
timer_gettime	105
timer_getoverrun	106
timer_delete	107
clock_settime	108
clock_gettime	109
clock_getres	10a
clock_nanosleep	10b
tgkill	10e
utimes	10f
kexec_load	11b
waitid	11c
/* sys_setaltroot	11d */
add_key	11e
request_key	11f
keyctl	120
ioprio_set	121
ioprio_get	122
inotify_init	123
inotify_add_watch	124
inotify_rm_watch	125
migrate_pages	126
openat	127
mkdirat	128
mknodat	129
fchownat	12a
futimesat	12b
fstatat64	12c
unlinkat	12d
renameat	12e
linkat	12f
symlinkat	130
readlinkat	131
fchmodat	132
faccessat	133
getcpu	13e

//EOF Read More...

位域

位域是C语言里面比较高级的特性，在结构体中比较常见。
现在在嵌入式开发中还比较常用，主要是能够节约内存空间。
如：

typedef struct {
    short int    flag_a: 1;    /* 在内存中只占 1 bit
                               * 超出可能会向高位覆写
                               * 但也可能丢失高位，由编译器而定 */
    short int    flag_b: 1;    /* 占 1 bit */
    short int    flag_c: 4;    /* 占 4 bits */
    short int    flag_d: 2;    /* 占 2 bits */
    short int    flag_e;       /* 占 16 bits */
} flags;
/* 这里整个结构体在内存中只占用了 4 Bytes */
/* 但还要注意：分配内存时还要考虑内存对齐原则，
 * 如，上面 flag_d 之后到 flag_e 之间，内存还有 8bits 的空余。
 * 所以 请尽量把位域字段放在一块儿！
 * 如果在 flag_e 之后再添加一个 flag_f: 8 的话，空间是只会向后扩展
 * 而不会插入 flag_d 和 flag_e 之间空余空间的。
 */

// EOF Read More...