信息安全系统设计基础第十一周学习总结

#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;
}

• waitdome2

#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());  //进程数？

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

 

• testsystem

#include    <stdlib.h> //功能貌似是一次执行两个命令

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

    system(argv[1]);
    system(argv[2]);
    return EXIT_SUCCESS;
}                /* ----------  end of function main  ---------- */

 

• testpp

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char **pp;
    pp[0] = malloc(20); //向内存申请访问空间，运行出错就是因为分配空间出问题了

    return 0;
}

 

• testpid

#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;
}

 

 

• testbuf1

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

 

• testbuf2

#include <stdio.h>
int main()
{
 printf("hello\n");  //和上一个代码相比少了清缓冲
 while(1);
}

 

• testbuf3

#include <stdio.h>

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

 

• psh1

#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;
}