範例: 如何使用指標指向指標陣列(Pointer Array)

array4.c

#include
#include
#include

struct abc {
int val;
char str[10];
};

void allocatemem(void*** a1) {
int amount;

printf("s1 - &a1: %10p, a1: %10p, *a1: %10p\n", a1, *a1, **a1);
amount = sizeof(struct abc)*16;
if ((*a1=(void**)malloc(amount))==NULL) {
printf("errno: %s, desc: %s\n", errno, strerror(errno));
}
printf("s2 - &a1: %10p, a1: %10p, *a1: %10p\n", a1, *a1, **a1);

memset(*a1, 0, amount);
//printf("memset ok\n");
printf("s4 - &a1: %10p, a1: %10p, *a1: %10p\n", a1, *a1, **a1);

}

int main(int argc, char** argv) {
struct abc *(*a1)[16];
printf("s0 - &a1: %10p, a1: %10p, &a1[0]: %10p, a1[0]: %10p, *a1: %10p , **a1: %10p, a1[1]: %10p\n", &a1, a1, &a1[0], a1[0], *a1, **a1, a1[1]);
allocatemem((void***)&a1);
printf("s5 - &a1: %10p, a1: %10p, &a1[0]: %10p, a1[0]: %10p, *a1: %10p , **a1: %10p, a1[1]: %10p\n", &a1, a1, &a1[0], a1[0], *a1, **a1, a1[1]);

return 0;
}

# gcc -g -o a4 ./array4.c

執行結果
# ./a4
s0 - &a1: 0xfeeac584, a1: 0x943c80, &a1[0]: 0x943c80, a1[0]: 0x943c80, *a1: 0x943c80 , **a1: (nil), a1[1]: 0x943cc0
s1 - &a1: 0xfeeac584, a1: 0x943c80, *a1: (nil)
s2 - &a1: 0xfeeac584, a1: 0x8aa5008, *a1: (nil)
s4 - &a1: 0xfeeac584, a1: 0x8aa5008, *a1: (nil)
s5 - &a1: 0xfeeac584, a1: 0x8aa5008, &a1[0]: 0x8aa5008, a1[0]: 0x8aa5008, *a1: 0x8aa5008 , **a1: (nil), a1[1]: 0x8aa5048

variable 在function 傳值的情形

m1.c show the memory usage status

#include
#include
#include

void allo(void** m1){
printf("s1 - &m1: %8p, m1: %8p\n", m1, *m1);
if ((*m1=(void*)malloc(sizeof(char)))==NULL) {
printf("errno: %s, desc: %s\n", errno, strerror(errno));
}
printf("s2 - &m1: %8p, m1: %8p\n", m1, *m1);
}

int main(int argc, char **argv) {
char *m1;
printf("s0 - &m1: %8p, m1: %8p\n", &m1, m1);
allo((void**)&m1);
printf("s3 - &m1: %8p, m1: %8p\n", &m1, m1);
return 0;
}


執行結果
# ./m1
s0 - &m1: 0xfee68534, m1: 0x943c80
s1 - &m1: 0xfee68534, m1: 0x943c80
s2 - &m1: 0xfee68534, m1: 0x9a07008
s3 - &m1: 0xfee68534, m1: 0x9a07008

SIP phone software

MyYahoo

Yahoo官方的Java
Web IM

http://my.yahoo.com/index.html

Gmail Chat

"POST /mail/channel/bind"

wengo

http://www.wengophone.com/

http://www.openwengo.com/

http://www.wengo.com/

xlite

http://www.counterpath.com/

download xlite

http://www.counterpath.com/index.php?menu=download

http://www.counterpath.com/index.php?menu=products&smenu=download

Express Talk

http://www.nch.com.au/index.html

download express talk

http://www.nch.com.au/talk/be.html

ㄧ堆sip phones

http://allvoipsearch.com/voipcheap.html

如何在 bash 中利用 array 來做array elements merging

#!/bin/sh

declare -a a
declare -a b
a=(1 2 3)
b=(4 5 6)
c="$a $b"
d="${a[@]} ${b[@]}"
e="${a[*]} ${b[*]}"
#echo ${a}
#echo ${a[0]}
#echo ${a[1]}
#echo ${a[2]}
#echo ${a[@]}
#echo ${a[*]}
#echo $b
echo $c
echo $d
echo $e

fork 出去的process 要和 parent process 溝通可以用下列方法

* pipe
* shared memory
* unix domain socket
* netlink socket

unix domain socket example
http://www.uwsg.iu.edu/hypermail/linux/kernel/0202.0/0515.html

#include
#include
#include
#include
#include
#include
#include
#include
#include

int main(int argc, char *argv[])
{
char buf[1];
int s;
int retval;
struct sockaddr_un server;

if (argc < 2)
printf("Usage : test socketname");

s = socket(PF_UNIX, SOCK_STREAM, 0);
if (s < 0)
perror("socket :");
else
{
server.sun_family = PF_LOCAL;
strncpy(server.sun_path, argv[1], sizeof(server.sun_path));

if (connect(s,(struct sockaddr *)&server,SUN_LEN(&server)) < 0)
perror("connect :");
else
{
retval = recv(s,buf,0, 0);
if (retval < 0)
perror("recv :");
else
printf("Received %u bytes.",retval);

close(s);
return 0;
}
}
}

Linux Command - lsof, ps

lsof
看linux opened socket, open fd 等resource 的conmmand

Use lsof command or /proc/PID file system to display fd lists:
# lsof -p 28290
OR
# cd /proc/28290/fd
# ls -l | less
You can count open file, enter:
# ls -l | wc -l
Show all connections with -i
# lsof -i
similar commands
# netstat -anp

Show threads in the current system
# ps -eLf




Show Your Network Connections

Show all connections with -i
lsof -i

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
dhcpcd 6061 root 4u IPv4 4510 UDP *:bootpc
sshd 7703 root 3u IPv6 6499 TCP *:ssh (LISTEN)
sshd 7892 root 3u IPv6 6757 TCP 10.10.1.5:ssh->192.168.1.5:49901 (ESTABLISHED)


Show only TCP (works the same for UDP)
lsof -iTCP

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 7703 root 3u IPv6 6499 TCP *:ssh (LISTEN)
sshd 7892 root 3u IPv6 6757 TCP 10.10.1.5:ssh->192.168.1.5:49901 (ESTABLISHED)


-i :port shows all networking related to a given port
lsof -i :22

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 7703 root 3u IPv6 6499 TCP *:ssh (LISTEN)
sshd 7892 root 3u IPv6 6757 TCP 10.10.1.5:ssh->192.168.1.5:49901 (ESTABLISHED)


To show connections to a specific host, use @host
lsof -i@192.168.1.5

sshd 7892 root 3u IPv6 6757 TCP 10.10.1.5:ssh->192.168.1.5:49901 (ESTABLISHED)


Show connections based on the host and the port using @host:port
lsof -i@192.168.1.5:22

sshd 7892 root 3u IPv6 6757 TCP 10.10.1.5:ssh->192.168.1.5:49901 (ESTABLISHED)


Grepping for "LISTEN" shows what ports your system is waiting for connections on
lsof -i| grep LISTEN

iTunes 400 daniel 16u IPv4 0x4575228 0t0 TCP *:daap (LISTEN)


Grepping for "ESTABLISHED" shows current active connections
lsof -i| grep ESTABLISHED

firefox-b 169 daniel 49u IPv4 0t0 TCP 1.2.3.3:1863->1.2.3.4:http (ESTABLISHED)



Working with Users, Processes, and Files

You can also get information on various users, processes, and files on your system using lsof:
Show what a given user has open using -u
lsof -u daniel

-- snipped --
Dock 155 daniel txt REG 14,2 2798436 823208 /usr/lib/libicucore.A.dylib
Dock 155 daniel txt REG 14,2 1580212 823126 /usr/lib/libobjc.A.dylib
Dock 155 daniel txt REG 14,2 2934184 823498 /usr/lib/libstdc++.6.0.4.dylib
Dock 155 daniel txt REG 14,2 132008 823505 /usr/lib/libgcc_s.1.dylib
Dock 155 daniel txt REG 14,2 212160 823214 /usr/lib/libauto.dylib
-- snipped --


See what files and network connections a command is using with -c
lsof -c syslog-ng

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
syslog-ng 7547 root cwd DIR 3,3 4096 2 /
syslog-ng 7547 root rtd DIR 3,3 4096 2 /
syslog-ng 7547 root txt REG 3,3 113524 1064970 /usr/sbin/syslog-ng
syslog-ng 7547 root mem REG 0,0 0 [heap]
syslog-ng 7547 root mem REG 3,3 105435 850412 /lib/libpthread-2.4.so
syslog-ng 7547 root mem REG 3,3 1197180 850396 /lib/libc-2.4.so
syslog-ng 7547 root mem REG 3,3 59868 850413 /lib/libresolv-2.4.so
syslog-ng 7547 root mem REG 3,3 72784 850404 /lib/libnsl-2.4.so
syslog-ng 7547 root mem REG 3,3 32040 850414 /lib/librt-2.4.so
syslog-ng 7547 root mem REG 3,3 126163 850385 /lib/ld-2.4.so
-- snipped --


Pointing to a file shows what's interacting with that file

lsof /var/log/messages

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
syslog-ng 7547 root 4w REG 3,3 217309 834024 /var/log/messages


The -p switch lets you see what a given process ID has open, which is good for learning more about unknown processes
lsof -p 10075

-- snipped --
sshd 10068 root mem REG 3,3 34808 850407 /lib/libnss_files-2.4.so
sshd 10068 root mem REG 3,3 34924 850409 /lib/libnss_nis-2.4.so
sshd 10068 root mem REG 3,3 26596 850405 /lib/libnss_compat-2.4.so
sshd 10068 root mem REG 3,3 200152 509940 /usr/lib/libssl.so.0.9.7
sshd 10068 root mem REG 3,3 46216 510014 /usr/lib/liblber-2.3
sshd 10068 root mem REG 3,3 59868 850413 /lib/libresolv-2.4.so
sshd 10068 root mem REG 3,3 1197180 850396 /lib/libc-2.4.so
sshd 10068 root mem REG 3,3 22168 850398 /lib/libcrypt-2.4.so
sshd 10068 root mem REG 3,3 72784 850404 /lib/libnsl-2.4.so
sshd 10068 root mem REG 3,3 70632 850417 /lib/libz.so.1.2.3
sshd 10068 root mem REG 3,3 9992 850416 /lib/libutil-2.4.so
-- snipped --

The -t option returns just a PID
lsof -t -c Mail

350

ps aux | grep Mail

daniel 350 0.0 1.5 405980 31452 ?? S Mon07PM 2:50.28 /Applications/Mail.app



time_t definition 尋根

user space 的 time_t 到底是如何定義的?

原來是定義在 kernel 當中


linux/include/asm-i386/posix_types.h:typedef long __kernel_time_t;
==> 先 define __kernel_time_t 為 long

linux/include/linux/types.h:typedef __kernel_time_t time_t;
==> 再 define time_t 為 __kernel_time_t

所以 time_t 就是 long (for i386 architecture) :)


[root@localhost linux]# grep -R -H "suseconds_t" ./*
./types.h:typedef __kernel_suseconds_t suseconds_t;
[root@localhost linux]# cd ../asm-i386/
[root@localhost asm-i386]# grep -R -H "__kernel_suseconds_t" ./*
./posix_types.h:typedef long __kernel_suseconds_t;

結論是
time_t
suseconds_t
都是 long 的型態