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8.0

Signal handling in Linux with C

Asked by paddy8788 in Signal Processing, C Programming Language, Linux Programming

Tags: C, Linux, signal Unix

Hi!
I am doing my project to develop a simple shell. I have a problem with handling signals that I hope you guys can help me.

I am using signal() function to catch the signal sending from the forked children to the shell, which is:
            signal(SIGCHLD, handler);
However, this is really confusing. When the user input a command into my shell, normally the shell parse it and call the corresponding programs. However, when I have a pipe like:
ls | cat | cat | cat | cat > a.txt
Then there are multiple files running at once, and the signal handler does not seem to be able to catch multiple signal at one time...

I tried to use signal mask in my handler (in the code snippet).      

But this does not seem help... I also applied the race running idea with signal suspend function to delay the moment the child return the signal but also, it does not work because I think at some moment, two child sends two SIGCHLDs at once, and that is really hard to control...
Right now, what I am doing is ask for the children to wait 1 second before sending any signals to the parent, and this works actually. But I don't think this is a smart way to handle signal...

I hope you can help me. Thank you!

Thank you! 
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sigset_t nmask, omask;	
	sigemptyset(&nmask);
	sigaddset(&nmask, SIGCHLD);
	signal(SIGCHLD, handler);
	sigprocmask(SIG_BLOCK, &nmask, &omask);			//Block all SIGCHLD signals
	/* My main code goes here */
	sigprocmask(SIG_SETMASK, &omask, NULL);			//Unblock SIGCHLD
[+][-]11/25/08 12:58 AM, ID: 23033138Accepted Solution

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About this solution

Zones: Signal Processing, C Programming Language, Linux Programming
Tags: C, Linux, signal Unix
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Solution Provided By: duncan_roe
Participating Experts: 2
Solution Grade: A
 
[+][-]11/24/08 07:13 PM, ID: 23032208Expert Comment

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[+][-]11/04/09 11:19 PM, ID: 25747342Administrative Comment

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