8.8
A.fork()
B.longjmp()
C.setjmp()
Warning:The function execv() doesn't belongs to group B! It should be called once returns once or never returns.
8.9
x=4
x=3
x=2
8.10
Three
8.11
Five
8.12
counter = 2
8.13
Maybe like this:
Hello
0
1
Bye
1
Bye
Also,maybe so:
Hello
1
Bye
0
1
Bye
8.14
E
8.15
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc,char**argv,char**envp){
if((setenv("COLUMNS","60",1))==-1){
fprintf(stderr,"setenv() error!\n");
exit(-1);
}
if((execve("/bin/ls",argv,envp))==-1){
fprintf(stderr,"execve() error!\n");
exit(-1);
}
exit(0);
}
8.16
/* $begin waitpid1 */
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#define N 2
int main()
{
int status, i;
pid_t pid[N];
for (i = 0; i < N; i++)
if ((pid[i] = fork()) == 0) /* child */
pause();/*wait for a signal*/
i=0;
while((kill(pid[i++],SIGSEGV))==0);/*send SIGSEGV signal to its children*/
/* parent waits for all of its children to terminate */
i=0;
while ((pid[i] = waitpid(-1, &status, 0)) > 0 && i<N) {
if (WIFEXITED(status))
printf("child %d terminated normally\n", pid[i]);
else
printf("child %d terminated by signal %d : %s\n",
pid[i], WTERMSIG(status),sys_siglist[WTERMSIG(status)]);
i++;
}
if (errno != ECHILD){
fprintf(stderr,"waitpid error");
exit(-1);
}
exit(0);
}
/* $end waitpid1 */
8.17
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
int mysystem(char*);
int mysystem(char* command){
int status;
pid_t pid;
if((pid=fork())==0){
execl("/bin/sh","sh","-c",command,NULL);
}/*notice here!Need NOT exit()!Read man pages of execl()*/
waitpid(-1,&status,0);
if(WIFEXITED(status))
return (WEXITSTATUS(status));
else
return (WTERMSIG(status));
}
int main(int argc,char **argv){
int i=mysystem(argv[1]);
printf("i= %d\n",i);
exit(i);
}
8.18
Of course, I can. In fact,the parent only receive 2 signals. When the parent receives the first SIGUSR2 signal, it calls the handler to handle it.At the same time,the second signal arrives. This signal is blocked and becomes a pending one.When the third one, the forth one and the fifth one arrive,they are all discarded simply. When handling the first one is finished, it is forced to receive the second one and handle it.That's all.