20135328陈都信息安全系统设计基础第十二周学习总结

20135328陈都信息安全系统设计基础第十二周学习总结

标签（空格分隔）：20135328陈都

第十二周（11.23-11.29）:

一、学习目标

掌握进程控制

掌握信号处理的方法

掌握管道和fifo进行进程间通信的方法

二、学习资源

编译、运行、阅读、理解process.tar.gz压缩包中的代码

exec1

#include <stdio.h>
#include <unistd.h>

int main()
{
char    *arglist[3];

arglist[0] = "ls";
arglist[1] = "-l";
arglist[2] = 0 ;//NULL
printf("* * * About to exec ls -l\n");
execvp( "ls" , arglist );,
printf("* * * ls is done. bye");

return 0;
}

exec3

代码如下：

#include <stdio.h>
#include <unistd.h>

int main()
{
char    *arglist[3];
char*myenv[3];
myenv[0] = "PATH=:/bin:";
myenv[1] = NULL;

arglist[0] = "ls";
arglist[1] = "-l";
arglist[2] = 0 ;
printf("* * * About to exec ls -l\n");

execlp("ls", "ls", "-l", NULL);
printf("* * * ls is done. bye\n");
}

forkdemo1

代码如下：

#include    <stdio.h>
#include<sys/types.h>
#include<unistd.h>
int main()
{
int ret_from_fork, mypid;
mypid = getpid();
printf("Before: my pid is %d\n", mypid);
ret_from_fork = fork();
sleep(1);
printf("After: my pid is %d, fork() said %d\n",
getpid(), ret_from_fork);

return 0;
}

forkdemo2

代码如下：

#include <stdio.h>
#include <unistd.h>

int main()
{
printf("before:my pid is %d\n", getpid() );
fork();
fork();
printf("aftre:my pid is %d\n", getpid() );

return 0;
}

forkdemo3

代码如下：

#include    <stdio.h>
#include    <stdlib.h>
#include    <unistd.h>

int main()
{
int fork_rv;

printf("Before: my pid is %d\n", getpid());

fork_rv = fork();       /* create new process   */

if ( fork_rv == -1 )        /* check for error  */
perror("fork");
else if ( fork_rv == 0 ){
printf("I am the child.  my pid=%d\n", getpid());

exit(0);
}
else{
printf("I am the parent. my child is %d\n", fork_rv);
exit(0);
}

return 0;
}

forkdemo4

代码：

#include    <stdio.h>
#include    <stdlib.h>
#include    <unistd.h>

int main()
{
int fork_rv;

printf("Before: my pid is %d\n", getpid());

fork_rv = fork();       /* create new process   */

if ( fork_rv == -1 )        /* check for error  */
perror("fork");

else if ( fork_rv == 0 ){
printf("I am the child.  my pid=%d\n", getpid());
printf("parent pid= %d, my pid=%d\n", getppid(), getpid());
exit(0);
}

else{
printf("I am the parent. my child is %d\n", fork_rv);
sleep(10);
exit(0);
}

return 0;
}

。

forkgdb

代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int  gi=0;
int main()
{
int li=0;
static int si=0;
int i=0;

pid_t pid = fork();
if(pid == -1){
exit(-1);
}
else if(pid == 0){
for(i=0; i<5; i++){
printf("child li:%d\n", li++);
sleep(1);
printf("child gi:%d\n", gi++);
printf("child si:%d\n", si++);
}
exit(0);

}
else{
for(i=0; i<5; i++){
printf("parent li:%d\n", li++);
printf("parent gi:%d\n", gi++);
sleep(1);
printf("parent si:%d\n", si++);
}
exit(0);

}
return 0;
}

psh1

代码：

#include    <stdio.h>
#include    <stdlib.h>
#include    <string.h>
#include    <unistd.h>

#define MAXARGS     20
#define ARGLEN      100

int execute( char *arglist[] )
{
execvp(arglist[0], arglist);
perror("execvp failed");
exit(1);
}

char * makestring( char *buf )
{
char    *cp;

buf[strlen(buf)-1] = '\0';
cp = malloc( strlen(buf)+1 );
if ( cp == NULL ){
fprintf(stderr,"no memory\n");
exit(1);
}
strcpy(cp, buf);
return cp;
}

int main()
{
char    *arglist[MAXARGS+1];
int     numargs;
char    argbuf[ARGLEN];

numargs = 0;
while ( numargs < MAXARGS )
{
printf("Arg[%d]? ", numargs);
if ( fgets(argbuf, ARGLEN, stdin) && *argbuf != '\n' )
arglist[numargs++] = makestring(argbuf);
else
{
if ( numargs > 0 ){
arglist[numargs]=NULL;
execute( arglist );
numargs = 0;
}
}
}
return 0;
}

psh2

代码：

#include    <stdio.h>
#include    <stdlib.h>
#include    <string.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>
#include    <signal.h>

#define MAXARGS     20
#define ARGLEN      100

char *makestring( char *buf )
{
char    *cp;

buf[strlen(buf)-1] = '\0';
cp = malloc( strlen(buf)+1 );
if ( cp == NULL ){
fprintf(stderr,"no memory\n");
exit(1);
}
strcpy(cp, buf);
return cp;
}

void execute( char *arglist[] )
{
int pid,exitstatus;

pid = fork();
switch( pid ){
case -1:
perror("fork failed");
exit(1);
case 0:
execvp(arglist[0], arglist);
perror("execvp failed");
exit(1);
default:
while( wait(&exitstatus) != pid )
;
printf("child exited with status %d,%d\n",
exitstatus>>8, exitstatus&0377);
}
}

int main()
{
char    *arglist[MAXARGS+1];
int     numargs;
char    argbuf[ARGLEN];

numargs = 0;
while ( numargs < MAXARGS )
{
printf("Arg[%d]? ", numargs);
if ( fgets(argbuf, ARGLEN, stdin) && *argbuf != '\n' )
arglist[numargs++] = makestring(argbuf);
else
{
if ( numargs > 0 ){
arglist[numargs]=NULL;
execute( arglist );
numargs = 0;
}
}
}
return 0;
}

testbuf1

代码如下：

#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("hello");
fflush(stdout);
while(1);
}

效果是先输出hello，然后换行。之后不退出。

testbuf2

代码如下：

#include <stdio.h>
int main()
{
printf("hello\n");
while(1);
}

程序输出hello，无法退出。

testbuf3

代码如下：

#include <stdio.h>

int main()
{
fprintf(stdout, "1234", 5);
fprintf(stderr, "abcd", 4);
}

将内容格式化输出到标准错误、输出流中。结果如图：

testpid

代码如下：

#include <stdio.h>
#include <unistd.h>

#include <sys/types.h>

int main()
{
printf("my pid: %d \n", getpid());
printf("my parent's pid: %d \n", getppid());
return 0;
}

输出当前进程pid和当前进程的父进程的pid。

testpp

代码如下：

#include <stdio.h>
#include <stdlib.h>
int main()
{
char **pp;
pp[0] = malloc(20);

return 0;
}

testsystem

代码如下：

#include    <stdlib.h>

int main ( int argc, char *argv[] )
{

system(argv[1]);
system(argv[2]);
return EXIT_SUCCESS;
}               /* --------

waitdemo1

代码如下：

#include    <stdio.h>
#include    <stdlib.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>

#define DELAY   4

void child_code(int delay)
{
printf("child %d here. will sleep for %d seconds\n", getpid(), delay);
sleep(delay);
printf("child done. about to exit\n");
exit(17);
}

void parent_code(int childpid)
{
int wait_rv=0;      /* return value from wait() */
wait_rv = wait(NULL);
printf("done waiting for %d. Wait returned: %d\n",
childpid, wait_rv);
}
int main()
{
int  newpid;
printf("before: mypid is %d\n", getpid());
if ( (newpid = fork()) == -1 )
perror("fork");
else if ( newpid == 0 )
child_code(DELAY);
else
parent_code(newpid);

return 0;
}

如果有子进程，则终止子进程，成功返回子进程pid。

waitdemo2

代码如下：

#include    <stdio.h>
#include    <stdlib.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>

#define DELAY   10

void child_code(int delay)
{
printf("child %d here. will sleep for %d seconds\n", getpid(), delay);
sleep(delay);
printf("child done. about to exit\n");
exit(27);
}

void parent_code(int childpid)
{
int wait_rv;
int child_status;
int high_8, low_7, bit_7;

wait_rv = wait(&child_status);
printf("done waiting for %d. Wait returned: %d\n", childpid, wait_rv);

high_8 = child_status >> 8;     /* 1111 1111 0000 0000 */
low_7  = child_status & 0x7F;   /* 0000 0000 0111 1111 */
bit_7  = child_status & 0x80;   /* 0000 0000 1000 0000 */
printf("status: exit=%d, sig=%d, core=%d\n", high_8, low_7, bit_7);
}

int main()
{
int  newpid;

printf("before: mypid is %d\n", getpid());

if ( (newpid = fork()) == -1 )
perror("fork");
else if ( newpid == 0 )
child_code(DELAY);
else
parent_code(newpid);
}

。

参考资料

《进程间通信-命名管道FIFO》（http://blog.csdn.net/xiajun07061225/article/details/8471777）

《linux i/o重定向与管道编程》

（http://blog.csdn.net/fulianzhou/article/details/48895327）

教材：第八章，详细学习指导：http://group.cnblogs.com/topic/73069.html

闫佳歆同学的博客：http://www.cnblogs.com/20135202yjx/p/5003653.html