03-03-2010
Quote:
Originally Posted by
karthigayan
Normally when we use fork the child will inherit the workspace of the parent.And also the child and the parent will run simultaneously.and any one can finish its process first.
Now come to your doubt,
Your while loop runs twice.Beginning of the loop you print some thing like " before fork():getpid()= 6010 " .When the first iteration a child process will get create.So the child and parent start to run simultaneously.So the statements can print in any order.
So the child have a provision the iterate the loop.So it will print the "before fork statement" .When the next iteration of the loop also the "bofore fork will get print.And the child process will get create and the appropriate statements will get print.
When the try for the next iteration the condition will get false.So it will come out.
Here :
One of the "before fork" statement is printed by the child process.
is there any technique to print the statements in the right order.
by right order i mean : to print the statements that come under same process rather than printing randomly.
i am unable to understand the process concept it self.
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FORK(2) System Calls Manual FORK(2)
NAME
fork - create a new process
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
pid_t fork(void)
DESCRIPTION
Fork causes creation of a new process. The new process (child process) is an exact copy of the calling process except for the following:
The child process has a unique process ID.
The child process has a different parent process ID (i.e., the process ID of the parent process).
The child process has its own copy of the parent's descriptors. These descriptors reference the same underlying objects, so that,
for instance, file pointers in file objects are shared between the child and the parent, so that an lseek(2) on a descriptor in the
child process can affect a subsequent read or write by the parent. This descriptor copying is also used by the shell to establish
standard input and output for newly created processes as well as to set up pipes.
The child starts with no pending signals and an inactive alarm timer.
RETURN VALUE
Upon successful completion, fork returns a value of 0 to the child process and returns the process ID of the child process to the parent
process. Otherwise, a value of -1 is returned to the parent process, no child process is created, and the global variable errno is set to
indicate the error.
ERRORS
Fork will fail and no child process will be created if one or more of the following are true:
[EAGAIN] The system-imposed limit on the total number of processes under execution would be exceeded. This limit is configuration-
dependent. (The kernel variable NR_PROCS in <minix/config.h> (Minix), or <minix/const.h> (Minix-vmd).)
[ENOMEM] There is insufficient (virtual) memory for the new process.
SEE ALSO
execve(2), wait(2).
3rd Berkeley Distribution May 22, 1986 FORK(2)