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記得20年前家裏剛裝電話時,一線需要兩三千塊(RMB),後來裝電話越來越便宜直到免費。現在借助於Asterisk, FreePBX,可以在家構建自己的電話局,如果你在海外,通過自己的電話局可以非常方便的和國內或其他地方的親朋好友聯系。

 

下面給出在Ubuntu 12.04 上安裝Asterisk,FreePBX的基本步驟。

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kill()不僅可以向進程發送SIGKILL信號,也可以發送其他信號。

#include<signal.h>

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The Binder communicates between processes using a small custom kernel module. This is used instead of standard Linux IPC facilities so that we can efficiently model our IPC operations as "thread migration". That is, an IPC between processes looks as if the thread instigating the IPC has hopped over to the destination process to execute the code there, and then hopped back with the result.

The Binder IPC mechanism itself, however, is not actually implemented using thread migration. Instead, the Binder's user-space code maintains a pool of available threads in each process, which are used to process incoming IPCs and execute local events in that process. The kernel module emulates a thread migration model by propagating thread priorities across processes as IPCs are dispatched and ensuring that, if an IPC recurses back into an originating process, the IPC is handled by its originating thread.

In addition to IPC itself, the Binder's kernel module is also resposible for tracking object references across processes. This involves mapping from remote object references in one process to the real object in its host process, and making sure that objects are not destroyed as long as other processes hold references on them.

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# hcidump -x
< HCI Command: Vendor (0x3f|0x0280) plen 5
09 01 00 00 00

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1.安裝gcc編譯器
直接在終端執行sudo apt-get install gcc libc6-dev 安裝gcc(需要系統光碟),要不然連helloworld這麼簡單的都編譯不過,或者在編譯tar.gz檔時提示“C compiler cannot create executable”的錯誤。

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