Linux支持POSIX reliable signals和POSIX real-time signals。
信号处理
进程接受到信号之后会有一些默认的处理方式，如下为5种处理方式：
| type | description |
|---|---|
| Term | Default action is to terminate the process. |
| Ign | Default action is to ignore the signal. |
| Core | Default action is to terminate the process and dump core (see core(5)). |
| Stop | Default action is to stop the process. |
| Cont | Default action is to continue the process if it is currently stopped. |
若想改变signal的默认处理方式，可以看signal函数和sigaction函数。
发送信号
下面是一些系统调用或者库函数可以用于发送信号给某进程：
| 系统调用或库函数 | 描述 |
|---|---|
| raise | Sends a signal to the calling thread. |
| kill | Sends a signal to a specified process, to all members of a specified process group, or to all processes on the system. |
| killpg | Sends a signal to all of the members of a specified process group. |
| pthread_kill | Sends a signal to a specified POSIX thread in the same process as the caller. |
| tgkill | Sends a signal to a specified thread within a specific process. (This is the system call used to implement pthread_kill(3).) |
| sigqueue | Sends a real-time signal with accompanying data to a specified process. |
信号类型
Linux支持的信号很多，常用的有如下这些：
| Signal | Value | Action | Comment |
|---|---|---|---|
| SIGHUP | 1 | Term | Hangup detected on controlling terminal or death of controlling process |
| SIGINT | 2 | Term | Interrupt from keyboard |
| SIGQUIT | 3 | Core | Quit from keyboard |
| SIGILL | 4 | Core | Illegal Instruction |
| SIGABRT | 6 | Core | Abort signal from abort(3) |
| SIGFPE | 8 | Core | Floating point exception |
| SIGKILL | 9 | Term | Kill signal |
| SIGSEGV | 11 | Core | Invalid memory reference |
| SIGPIPE | 13 | Term | Broken pipe: write to pipe with no readers |
| SIGALRM | 14 | Term | Timer signal from alarm(2) |
| SIGTERM | 15 | Term | Termination signal |
| SIGUSR1 | 30,10,16 | Term | User-defined signal 1 |
| SIGUSR2 | 31,12,17 | Term | User-defined signal 2 |
| SIGCHLD | 20,17,18 | Ign | Child stopped or terminated |
| SIGCONT | 19,18,25 | Cont | Continue if stopped |
| SIGSTOP | 17,19,23 | Stop | Stop process |
| SIGTSTP | 18,20,24 | Stop | Stop typed at terminal |
| SIGTTIN | 21,21,26 | Stop | Terminal input for background process |
| SIGTTOU | 22,22,27 | Stop | Terminal output for background process |
其中value是可能的取值，因为在不同的系统上它的值不一样，最好使用宏进行操作比较安全，移植性也需要考虑。