Is there a way to send some procesess with known pid in background?

I am new in开发者_JS百科 Linux and system programming . I Want to write a c program which finds processes whose cpu% usage are more than a specific given value and sends them to background.

anybody can help me ! I really appreciate it

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I'm fairly sure that what you're asking is that you want to detect if a process is using X amount of CPU and if so, take it off the CPU for a while. There's a piece of software already that does this: It's called the kernel. I'm not aware of any way to programatically take another process off CPU unless that other program supports an external interface to reduce its load.

Most likely what you really want to do is configure the nice and other scheduler parameters of the running process so the kernel is more like to to take it off CPU when another program needs to do work.

But what underlying problem are you really trying to solve here? Maybe if you tell us that we can offer an alternate solution.

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Please look at source code of process managament utilities like:

• htop
• top (standard unix command)
• ps (standard unix command)

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IMHO, You can't.

Background management ensures the shell. So, the & is interpreted for example by /bin/bash command. When pressed CTRL-Z, the kernel stopping your current fg-job, and again by your shell you can send it into background.

Youre looking for the way how to remote control the shell what running some program in fg. I don't know any 'remote-controling' way.

Ofc, here are alternative solutions, for example:

• use the screen command, and you can recall the specific screen into your terminal, and can manually send process into bg.
• or you can use some screen-sharing utility, to overtake a specific terminal and CTRL-Z, bg
• or, you can patch bash and adding remote control functionality. ;)

or, here is something what i don't know. ;) - hm, maybe trap some user-signal handling code in the /etc/profile?

You can read a bit about here: http://en.wikipedia.org/wiki/Process_group

Honestly, after a half hour of thinking I don't get any idea why you want remotely (from the another terminal - by its PID) send some processes from the fg into the bg. Give me no sense.

Can you please tell, what you want achieve?

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You probably want to reduce process priority, but I not sure it's good idea.

We send process to background generally to free shell's prompt.

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The "+" means that the program "is in the foreground process group". I don't believe, however, that this state at all affects the process's scheduling.

However, you can change it with tcsetpgrp.

From the man page: "The function tcsetpgrp() makes the process group with process group ID pgrp the foreground process group on the terminal associated to fd, which must be the controlling terminal of the calling process, and still be associated with its session. Moreover, pgrp must be a (non-empty) process group belonging to the same session as the calling process."

By my reading, you just call this function and make the shell (or some other program) be the foreground process.