study

Author: wenjun1055

10.1.c

@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+
+static void sig_usr(int);
+
+int main(void)
+{
+    if (signal(SIGUSR1, sig_usr) == SIG_ERR) {
+        printf("can't catch SIGUSR1");
+        exit(-1);
+    }
+
+    if (signal(SIGUSR2, sig_usr) == SIG_ERR) {
+        printf("can't catch SIGUSR2");
+        exit(-1);
+    }
+
+    for ( ; ; )
+        pause();
+}
+
+static void sig_usr(int signo)
+{
+    if (signo == SIGUSR1) {
+        printf("received SIGUSR1\n");
+    } else if (signo == SIGUSR2) {
+        printf("received SIGUSR2");
+    } else {
+        printf("received signal %d\n", signo);
+    }
+}

10.2.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <pwd.h>
+#include <string.h>
+
+static void my_alarm(int signo)
+{
+    struct passwd  *rootptr;
+
+    printf("in signal handler\n");
+    if (NULL == (rootptr = getpwnam("root"))) {
+        printf("getpwnam(root) error\n");
+        exit(-1);
+    }
+
+    alarm(1);
+}
+
+int main(void)
+{
+    struct passwd   *ptr;
+    
+    signal(SIGALRM, my_alarm);
+    alarm(1);
+
+    for (; ;) {
+        if (NULL == (ptr = getpwnam("vagrant"))) {
+            printf("getpwnam error\n");
+            exit(-1);
+        }
+
+        if (strcmp(ptr->pw_name, "vagrant") != 0) {
+            printf("return value corrupted, pw_name = %s\n", ptr->pw_name);
+        }
+    }
+}

8.8.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+char    *env_init[] = {"USER=unknown", "PATH=/tmp", NULL};
+
+int main(void)
+{
+    pid_t   pid;
+
+    if ((pid = fork()) < 0) {
+        printf("fork error\n");
+        exit(-1);
+    } else if (0 == pid) {
+        if (execle("/home/sar/bin/echoall", "echoall", "myarg1", "MY ARG2", (char *)0, env_init) < 0) {
+            printf("execle error\n");
+            exit(-1);
+        }
+    }
+
+    if (waitpid(pid, NULL, 0) < 0) {
+        printf("wait error\n");
+        exit(-1);
+    }
+
+    if ((pid = fork()) < 0) {
+        printf("fork error\n");
+        exit(-1);
+    } else if (0 == pid) {
+        if (execlp("echoall", "echoall", "only 1 arg", (char *)0) < 0) {
+            printf("ececlp error\n");
+            exit(-1);
+        }
+    }
+
+    return 0;
+}