. 1.
:
, . , : , , .
1. :
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int i;
for(i = 0; i <3; i++)
{
pid_t pid = fork();
printf("I am process %d, My parent is %d\n", getpid(), getppid());
}
7 .
| 1 | 2 | 11 | ||
| i=0 | 1 | - | - | - |
| i=1 | 2 | 11 | - | - |
| i=2 | 3 | 12 | 21 | 111 |
 |
2.
% (echo ' 1'; echo ' 2') > plan.txt
:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(){
FILE *fp;
char str[80];
fp = fopen("plan.txt", "r");
if(fp == NULL)
{
fprintf(stderr, "Could not open file");
exit(1);
}
fgets(str, 80, fp);
printf("Parent reads: %s\n", str);
if(fork() == 0)
{
fgets(str, 80, fp);
printf("Child Reads: %s\n", str);
}
fclose(fp);
}
, ?
, ..
fork,
.
, .
:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(void)
{
FILE *fp;
fp = fopen("plan.txt","w");
if(fp == NULL)
{
fprintf(stderr,"Could not open file");
exit(1);
}
fprintf(fp," \n");
if(!fork())
{
fprintf(fp," \n");
}
fclose(fp);
}
2. 
, , . .
 |  | ||
:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(void)
{
int pid_1;
int pid_11;
int pid_12;
int pid_2;
int pid_21;
int pid_22;
int status;
pid_1=fork();
if (pid_1== 0)
{
pid_11=fork();
|
|
|
if(pid_11==0)
printf("I am the second generation child process - %d. My parent is - %d\n", getpid(), getppid()); //
else
{
wait(&status);
pid_12=fork();
if(pid_12==0)
printf("I am the second generation child process - %d. My parent is - %d\n",getpid(),getppid());//
else
{
wait(&status);
printf("I am the first generation child process - %d. My parent is - %d\n",getpid(),getppid()); //
}
}
}
else
{
wait(&status);
pid_2=fork();
if(pid_2==0)
{
pid_21=fork();
if(pid_21==0)
printf("I am the second generation child process - %d. My parent is - %d\n",getpid(),getppid());//
else
{
wait(&status);
pid_22=fork();
if(pid_22==0)
printf("I am the second generation child process - %d. My parent is - %d\n",getpid(),getppid()); //
else
{
wait(&status);
printf("I am the first generation child process - %d. My parent is - %d\n",getpid(),getppid()); //
}
}
}
else
{
wait(&status);
printf("I am the parent process - %d.\n",getpid()); //
}
}
}
:
I am the second generation child process - 4083. My parent is - 4082
I am the second generation child process - 4084. My parent is - 4082
I am the first generation child process - 4082. My parent is - 4081
I am the second generation child process - 4086. My parent is - 4085
I am the second generation child process - 4087. My parent is - 4085
I am the first generation child process - 4085. My parent is - 4081
I am the parent process - 4081.
. 2.
:
. , : , , .
.
1. , . :
.
fork
, exec .
exec exit(1)
:
exc21_1.
#include <stdio.h>
#include <unistd.h>
int main(void)
{
int pid=fork();
if(pid==0)
{
execv("exc21_2.ou",NULL);
printf ("EXEC Failed\n");
_exit(1);
}
else
printf("Parent id=%d and child id=%d\n",getpid(),pid);
}
exc21_2.
#include <stdio.h>
int main(void)
{
printf("Child id=%d\n",getpid());
}
:
Parent id=4566 and child id=4567
Child id=4567
2. , 2 - . . exit
|
|
|
exc22_1.
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
int main(void)
{
int status;
if(!fork())
{
execv("exc22_2.ou", NULL);
printf ("EXEC Failed\n");
_exit(1);
}
else
{
wait(&status);
printf("First child end\n");
if(!fork())
{
execv("exc22_3.ou", NULL);
printf ("EXEC Failed\n");
_exit(1);
}
else
{
wait(&status);
printf("Second child end\n");
}
}
}
exc22_2.
#include <stdio.h>
int main(void)
{
printf("Hello! I am first child\n");
}
exc22_3.
#include <stdio.h>
int main(void)
{
printf("Hello! I am second child\n");
}
:
Hello! I am first child
First child end
Hello! I am second child
Second child end
3. , .
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
int main(int argc, char * argv[])
{
int pid, status;
if (argc < 2)
{
printf("Usage: %s command, [arg1 [arg2]...]\n", argv[0]);
return EXIT_FAILURE;
}
printf("Starting %s...\n", argv[1]);
pid = fork();
if (pid == 0)
{
execvp(argv[1], &argv[1]);
perror("execvp");
return EXIT_FAILURE; // Never get there normally
}
else
{
if (wait(&status) == -1)
{
perror("wait");
return EXIT_FAILURE;
}
if (WIFEXITED(status))
printf("Child terminated normally with exit code %i\n", WEXITSTATUS(status));
if (WIFSIGNALED(status))
printf("Child was terminated by a signal #%i\n", WTERMSIG(status));
if (WCOREDUMP(status))
printf("Child dumped core\n");
if (WIFSTOPPED(status))
printf("Child was stopped by a signal #%i\n", WSTOPSIG(status));
}
return EXIT_SUCCESS;
}
:
user:~$./exec.ou ps
Starting ps...
PID TTY TIME CMD
2020 pts/1 00:00:00 bash
4919 pts/1 00:00:00 exec.ou
4920 pts/1 00:00:00 ps
Child terminated normally with exit code 0
: , , .
