Processes in Unix
Last updated
Last updated
The fork clones the executing process, creating a replica of it.
The address spaces of the two processes are equal.
actually, just after the fork, they are the same.
typically, a copy-on-write approach is followed.
The states of execution are the same.
including the program counter.
Some process variables are different (PID, PPID, ...).
The value returned by the fork is different in parent and child processes.
in the parent, it is the PID of the child.
in the child, it is always 0.
This return value can be used as a boolean variable.
so we can distinguish the code running on the child and parent.
In general, used alone, the fork is of little interest.
In general, we want to run a different program in the child.
exec system call.
there are different versions of exec.
Sometimes, we want the parent to wait for the conclusion of the program running in the child.
wait system call.
In this code, we are assuming the fork doesn’t fail.
in case of an error, it returns -1.
