add test_signal.c

Change-Id: Iad9a0eda64ecd7a2bd3519e3f6e54bbe9d127f85

Author: pk1206

notes/10/code/Makefile

@@ -1,15 +1,15 @@
-
-CC = gcc
-CFLAGS = -I../.. -Wall
-LDFLAGS = 
-LDLIBS =
-
-PROGS += 
-
-all: ${PROGS}
-
-%: %.c
-	$(CC) $(CFLAGS) $@.c -o $@ $(LDFLAGS) $(LDLIBS)
-
-clean:
-	rm -f $(PROGS) *.o
+
+CC = gcc
+CFLAGS = -I../.. -Wall
+LDFLAGS = 
+LDLIBS =
+
+PROGS += test_signal
+
+all: ${PROGS}
+
+%: %.c
+	$(CC) $(CFLAGS) $@.c -o $@ $(LDFLAGS) $(LDLIBS)
+
+clean:
+	rm -f $(PROGS) *.o

notes/10/code/test_signal.c

@@ -0,0 +1,59 @@
+#include <unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+void sig_chld(int signo)
+{
+    int status;
+    pid_t pid;
+    printf("signo = %d\n", signo);
+
+    while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
+    {
+        printf("%d exits, status = %d\n", pid, status);
+    }
+}
+
+int main()
+{
+    pid_t pid = 0;
+    void (*old_sig_chld)(int) = signal(SIGCHLD, sig_chld);
+    if (old_sig_chld == SIG_ERR)
+    {
+        printf("signal error, errno = %d, %s\n", errno, strerror(errno));
+        exit(errno);
+    }
+    else if (old_sig_chld == SIG_IGN)
+    {
+        printf("old SIGCHLD handler = SIG_IGN\n");
+    }
+    else if (old_sig_chld == SIG_DFL)
+    {
+        printf("old SIGCHLD handler = SIG_DFL\n");
+    }
+    else
+    {
+        printf("old SIGCHLD handler = %p\n", old_sig_chld);
+    }
+
+    pid = fork();
+    if (pid < 0)
+    {
+        printf("fork error, errno = %d, %s", errno, strerror(errno));
+        exit(errno);
+    }
+
+    if (pid == 0)
+    {
+        // child
+        exit(0);
+    }
+
+    sleep(2);
+
+    return 0;
+}

notes/10/notes.md

@@ -131,6 +131,8 @@ exec调用：
 fork调用：
 * 子进程继承父进程的信号处理方式。因为信号捕捉函数的地址在子进程中是有意义的。
 
+示例代码：<a href="code/test_signal.c">test_signal.c</a>
+
 ---
 
 [章节目录](../../README.md#title_ch10 "返回章节目录")