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    Yes, the fork creates a new PID, and the exec inherits the new number. Commented Sep 24, 2015 at 9:35
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    I don't understand your question. Everything is a process. Commented Sep 24, 2015 at 9:39
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    Your shell process runs fork to create a new process, when you hit enter, and then the new forked process runs exec with the command you wrote. Commented Sep 24, 2015 at 9:44
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    @ams, is fork() efficient? Say I have a large application that runs a simple process /bin/ls for example to take its output. All parent's memory will be duplicated just to be replaced from ls? Commented Feb 3, 2019 at 13:38
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    @Vassilis, it's not duplicated, it's shared. The only copying is a few page tables inside the kernel. If the child process attempts to write to memory, only then does the memory get duplicated, and only for that one page (about 4k, I think). Commented Feb 4, 2019 at 14:25