Duplicating Processes using Fork.

spatlou

Fork>
Syntax #include <sys/types.h>
#include <unistd.h>
pid_t fork(void);
The call to fork in the parent
returns the PID of the new child
process
The new process continues to execute just like the original
In the child process the call to fork returns 0
This helps to differentiate between the parent and child

ritug1992

program to convert lower case characters to upper case characters:

#include<stdio.h>

#include<string.h>

int main()

{

char str[20];

int i;

printf("Enter the string\n");

scanf("%s",str);

printf("The string is %s\n",str);

for(i=0; i <= strlen(str);i++)

{

if(str[i] >=97 && str[i] <= 122)

{

str[i] = str[i] -32;

}

printf("The string in upper case is %s",str);

return 0;

}

calling above program using system call:

#include<stdio.h>

#include<stdlib.h>

#include<unistd.h>

int main()

{

pid_t PId,PPid;

system("/home/ritu/emblogic/project_3/convert_lower_to_upper");

printf("PID is %d",getpid());

printf("PPid is %d",getppid());

return 0;

}

binayak2508

Program to implement process duplication and replacement

RCS file: execl.c,v
Working file: execl.c
head: 1.5
branch:
locks: strict
    root: 1.5
access list:
symbolic names:
keyword substitution: kv
total revisions: 5;    selected revisions: 5
description:
this a program to replace a process using execl
----------------------------
revision 1.5    locked by: root;
date: 2014/10/16 13:03:06; author: root; state: Exp; lines: +2 -1
*** empty log message ***
----------------------------
revision 1.4
date: 2014/10/16 12:55:05; author: root; state: Exp; lines: +1 -1
correcte name of 1st argument
----------------------------
revision 1.3
date: 2014/10/16 12:25:54; author: root; state: Exp; lines: +1 -1
fprintf changed to sprintf
----------------------------
revision 1.2
date: 2014/10/16 12:17:22; author: root; state: Exp; lines: +36 -0
fd of open file sent to replaced process
----------------------------
revision 1.1
date: 2014/10/16 11:04:47; author: root; state: Exp;
Initial revision
=============================================================================

HEADERFILE OF THE PROGRAM

RCS file: header.h,v
Working file: header.h
head: 1.3
branch:
locks: strict
    root: 1.3
access list:
symbolic names:
keyword substitution: kv
total revisions: 3;    selected revisions: 3
description:
this is a header to execl.c
----------------------------
revision 1.3    locked by: root;
date: 2014/10/16 12:21:19; author: root; state: Exp; lines: +3 -1
fcntl.h included
implemented sys/types.h
implemented sys/stat.h
----------------------------
revision 1.2
date: 2014/10/16 12:16:36; author: root; state: Exp; lines: +3 -0
stdlib.h included
unistd.h included
----------------------------
revision 1.1
date: 2014/10/16 11:03:15; author: root; state: Exp;
Initial revision
=============================================================================

binayak2508

implementation of system call wait() in process management

RCS file: wait.c,v
Working file: wait.c
head: 1.9
branch:
locks: strict
    root: 1.9
access list:
symbolic names:
keyword substitution: kv
total revisions: 9;    selected revisions: 9
description:
This is a program to check function of wait()
----------------------------
revision 1.9    locked by: root;
date: 2014/10/16 06:43:35; author: root; state: Exp; lines: +0 -1
removed break statements
----------------------------
revision 1.8
date: 2014/10/16 06:42:26; author: root; state: Exp; lines: +2 -1
exit_code declared
----------------------------
revision 1.7
date: 2014/10/16 06:39:28; author: root; state: Exp; lines: +21 -6
Included WIFEXITED macro
Included WEXITSTATUS macro
----------------------------
revision 1.6
date: 2014/10/16 06:08:08; author: root; state: Exp; lines: +10 -3
printed message for parent process
----------------------------
revision 1.5
date: 2014/10/16 06:01:37; author: root; state: Exp; lines: +4 -3
argument of msg created
----------------------------
revision 1.4
date: 2014/10/15 06:38:48; author: root; state: Exp; lines: +4 -2
sleep() statement included
----------------------------
revision 1.3
date: 2014/10/15 06:34:38; author: root; state: Exp; lines: +2 -2
declared n
----------------------------
revision 1.2
date: 2014/10/15 06:31:26; author: root; state: Exp; lines: +6 -2
wait() function is included
----------------------------
revision 1.1
date: 2014/10/15 06:23:50; author: root; state: Exp;
Initial revision
=============================================================================

spatlou

kartik.gupta

fork() is a system call used to create a new process (child process).

->the original process (parent process) is distinguished from child process from its return value.

->the child process pid is returned in the parent process and 0 is returned in child process.

->child process have its own process control block(unique PID) with an entry in process table.

->if process creation is failed then -1 is returned in the parent process.

->after the fork call ,both processes execute the same instructions following the fork call which is finally scheduled by scheduler.

->a separate virtual memory is allocated for the child process which is exact replica of parent process, both memory shares the same local ,global variables but if any of them modify the values it doesn't affect the value for another , this is generally called as COPY ON WRITE.

-> both processes share the file descriptors and thier attributes also(file offset position).

ra9501576600

@kartik.gupta

Q: Child process shares the same process context as is used by parent process. So, how come child process has the different Process Control Block (pid, ppid)? Is it anything to do with stack frames in process context?

And what is process table in physical? Where is resides?

spatlou

Duplicating Processes using Fork.

Program to implement process duplication and replacement

HEADERFILE OF THE PROGRAM

implementation of system call wait() in process management

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