fork(2) System Calls Manual fork(2)Name
fork - create a new process
Syntax
#include <sys/types.h>
#include <unistd.h>
pid = fork()
pid_t pid;
Description
The system call causes creation of a new process. The new process (child process) is an exact copy of the calling process except for the
following:
o The child process has a unique process ID.
o The child process has a different parent process ID (that is, the process ID of the parent process).
o 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 a 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.
o The child processes resource utilizations are set to 0. For further information, see
Return Values
Upon successful completion, 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.
Diagnostics
The system call fails and no child process are created under the following conditions:
[EAGAIN] The system-imposed limit {PROC_MAX} on the total number of processes under execution would be exceeded.
[EAGAIN] The system-imposed limit {CHILD_MAX} on the total number of processes under execution by a single user would be exceeded.
[ENOMEM] There is insufficient swap space for the new process.
See Alsoexecve(2), wait(2)fork(2)
Check Out this Related Man Page
FORK(2) Linux Programmer's Manual FORK(2)NAME
fork - create a child process
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
pid_t fork(void);
DESCRIPTION
fork creates a child process that differs from the parent process only in its PID and PPID, and in the fact that resource utilizations are
set to 0. File locks and pending signals are not inherited.
Under Linux, fork is implemented using copy-on-write pages, so the only penalty incurred by fork is the time and memory required to dupli-
cate the parent's page tables, and to create a unique task structure for the child.
RETURN VALUE
On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of exe-
cution. On failure, a -1 will be returned in the parent's context, no child process will be created, and errno will be set appropriately.
ERRORS
EAGAIN fork cannot allocate sufficient memory to copy the parent's page tables and allocate a task structure for the child.
ENOMEM fork failed to allocate the necessary kernel structures because memory is tight.
CONFORMING TO
The fork call conforms to SVr4, SVID, POSIX, X/OPEN, BSD 4.3.
SEE ALSO clone(2), execve(2), vfork(2), wait(2)Linux 1.2.9 1995-06-10 FORK(2)
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I.e for example by using fork() i need to run seperate 4 background processes..
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hello every one,
i want to know more about creation of child process.
UNDER WHAT CIRCUMSTANCES child process is created?
WHAT ARE THE PREREQUISITES for a child process to be created?
let us say we have a prog.c, prog.obj(compiled.c),.a\.out files.
is any child PROCESS CREATED... (12 Replies)
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I am running a webserver that uses sockets, forks, and children. The parent process listens for connections and the child processes the information.
I am trying to figure out why the code I have below SIGTERM, and SIGKILL never fire. I was messing around with the printfs and doesnt... (11 Replies)
hi all,
I am trying to find the process id of the subsequent process created via fork and exec calls in perl.
For eg:
envVarSetter dataCruncher.exe < input.txt > output.txt
When I fork and exec the above command,
it returns only the pid of envVarSetter and I don't know how to find the... (9 Replies)
All,
Ok...so I know I *should* be able to control a process's stdin and stdout from the parent by creating pipes and then dup'ing them in the child. And, this works with all "normal" programs that I've tried. Unfortunately, I want to intercept the stdin/out of the scp application and it seems... (9 Replies)
Hi all,
Im trying to do a simple program which ask the user for a unix command with the arguments. The program fork and the two process communicate with pipes. The child process call execvp with the command and the father process read the result of the execvp via the pipe.
This program works... (11 Replies)
if i run exec1 to execute a command such as ls; ls, then is there a way i can get a return value? If i am using pipes and the child process runs the exec1 line, how can the parent process know the return value of the result of exec1? (20 Replies)
Hi,
I have a unix script that basically has a while loop inside which it checks Oracle database for certain records. If it finds the records, it does some processing and then goes back to the while loop. If it doesnot find any matching records, then it sleeps for 30 seconds and then goes back to... (17 Replies)
Hi all,
I have a query on killing a child process, if it takes more than 10 minutes
myparent.sh has the following
#!/bin/sh
echo "My Parent Script"
home/guru/initiateServer.sh
The initiateServer is a child process and this might take 20 or more minutes to return. I want to kill this... (11 Replies)
Hi Folks -
Happy Thursday!
I have a need where I have Parent/Control script that calls multiple child scripts. The problem is, after the first child script is executed, it fails to move to the next script. I assume it's due to my script exit?
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Hi,
I am a newbie in Linux land, and I have a question about programming parent/child process interaction:
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