以下是signal()函式的宣告。
void (*signal(int sig, void (*func)(int)))(int)
sig -- 這是信號的處理功能被設定的號碼。以下是幾個重要的標準信號的數位：
| macro | signal |
|---|---|
| SIGABRT | (Signal Abort) Abnormal termination, such as is initiated by the function. |
| SIGFPE | (Signal Floating-Yiibai Exception) Erroneous arithmetic operation, such as zero divide or an operation resulting in overflow (not necessarily with a floating-yiibai operation). |
| SIGILL | (Signal Illegal Instruction) Invalid function image, such as an illegal instruction. This is generally due to a corruption in the code or to an attempt to execute data. |
| SIGINT | (Signal Interrupt) Interactive attention signal. Generally generated by the application user. |
| SIGSEGV | (Signal Segmentation Violation) Invalid access to storage: When a program tries to read or write outside the memory it is allocated for it. |
| SIGTERM | (Signal Terminate) Termination request sent to program. |
func -- 這是一個指向函式的指標。這可以是由程式員或一個以下預定義的函式的定義的函式：
| SIG_DFL | 預設處理：對於某一特定信號，該信號處理的預設操作。 |
| SIG_IGN | 忽略信號：信號被忽略。 |
這個函式返回前一個信號處理程式或錯誤SIG_ERR的值。
下面的例子顯示了signal()函式的用法。
#include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <signal.h> void sighandler(int); int main() { signal(SIGINT, sighandler); while(1) { printf("Going to sleep for a second... "); sleep(1); } return(0); } void sighandler(int signum) { printf("Caught signal %d, coming out... ", signum); exit(1); }
讓我們編譯和執行上面的程式，這將產生以下結果，程式將無限迴圈中去。跳出程式使用Ctrl + C鍵。
Going to sleep for a second... Going to sleep for a second... Going to sleep for a second... Going to sleep for a second... Going to sleep for a second... Caught signal 2, coming out...