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Whenever you write a program that prints its own process ID, I've always (without any exception) received numbers ranging in the tens of thousands. Never less, never higher.

I was just wondering, why is are the process ID #s so high? Are the ones below it all system-related processes?

And then when I run the program again, it prints out an ID that is several hundred above the previous execution... what happens between these two executions that come right after each other?

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migrated from Sep 13 '11 at 1:34

This question came from our site for professional programmers interested in conceptual questions about software development.

closed as not constructive by Linker3000, Nifle, random Sep 15 '11 at 2:38

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What operating systems are you asking about? I see many process IDs less than 1,000 on my Linux system, and all are under 10,000 on my Windows system. – David Schwartz Sep 12 '11 at 23:51
@David: Windows reuses pids. – Paul Nathan Sep 13 '11 at 2:49
Is there a certain algorithm that governs the reuse of pids? I'm assuming this also means there is a maximum number of processes than can be run... – Dark Templar Sep 13 '11 at 5:24
@Paul: And so does Linux. – grawity Sep 13 '11 at 7:45
@Dark: On Linux, PIDs wrap around at 32768 by default (adjustable through /proc/sys/kernel/pid_max, I think you can have full 4294967296 if you want) – grawity Sep 13 '11 at 7:46
up vote 10 down vote accepted

what happens between these two executions that come right after each other?

Several hundred other processes get run.

You are not the only user.

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