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Questions tagged [sigchld]

70 questions
20
votes
2 answers

Java signal chaining

I've got a program with a specialized Process-type class which handles executing the processes natively on Linux. It does not use Java's Process class at all, because it needs to do some special handling of the process. Because of this, it also…
rm5248
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1 answer

How can I handle SIGCHLD?

I need to handle SIGCHLD properly. How can I use it with my existing code? at the moment I cant wait for the child process unless I use 0 instead of WNOHANG|WUNTRACED. status = 0; pid_t child, endID; if(amp == 1) signal( SIGCHLD, SIG_IGN…
kanoz
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11
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1 answer

Not receiving SIGCHLD for processes executed with sudo

I'm currently in the process of writing a shell. I execute processes and utilize a SIGCHLD signal handler to clean up (wait on them) when they are complete. Everything has been working -- except when I execute processes which escalate privileges…
BSchlinker
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9
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2 answers

SIGCHLD Signal Processing

In Unix, when a child process in background terminates, it sends a SIGCHLD signal to the parent to inform it that it terminated. Does the same happen even if the process was in foreground? If so, this means the parent will just ignore it. Is this…
darksky
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8
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4 answers

What's the difference between various $SIG{CHLD} values?

What is the difference between these settings? $SIG{CHLD} = 'IGNORE' $SIG{CHLD} = 'DEFAULT' $SIG{CHLD} = '' $SIG{CHLD} = undef According to "Advanced Programming in the UNIX Environment, 2nd edition", figure 10.1 the default value of SIGCHLD…
Trueblood
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7
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1 answer

bash restart sub-process using trap SIGCHLD?

I've seen monitoring programs either in scripts that check process status using 'ps' or 'service status(on Linux)' periodically, or in C/C++ that forks and wait on the process... I wonder if it is possible to use bash with trap and restart the…
X.M.
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5
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2 answers

Is there a way to prevent only a specific child from triggering a SIGCHLD?

I'm writing a debugging utility, and I want to fork a child while preventing that child's termination from triggering a SIGCHLD to its parent. I still want other children to normally cause a SIGCHLD upon termination. I want to do this because I…
Moh
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4
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1 answer

Trapping CHLD signal - ZSH works but ksh/bash/sh don't?

Here's a sample code where a shell script launches a few jobs in the background and upon receiving the CHLD signal (i.e. the child process termination) it will take some actions... The problem is that if the parent shell script is a ZSH one, it…
Reza Toghraee
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4
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2 answers

SIGCHLD Replacement for Windows

I would like to have SIGCHLD functionality on Windows (i.e., notify the parent process when a child dies). I am aware that there is no equivalent to SIGCHLD in the Windows API, but I'd like to know what the common method is for implementing this…
Matt Fichman
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4
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1 answer

error: conflicting types for ‘wstat’ in gcc

I copied this program from this documentation: https://docs.oracle.com/cd/E19455-01/806-4750/signals-7/index.html #include #include #include #include void proc_exit() { int wstat; …
Ashot
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4
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2 answers

How To Avoid SIGCHLD error In Bash Script That Uses GNU Parallel

I'm running a script.sh in a loop. The script contains a parallel wget command. I'm getting the following error: Signal SIGCHLD received, but no signal handler set. The loop looks like this: for i in {1..5}; do /script.sh; done And the line that…
DomainsFeatured
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4
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2 answers

how a process know's which child ended?

when a process child is terminated he's sending a SIGCHLD to the parent process. Now, if the parent process have more than one child how the parent process knows which child had sent the signal?
orenma
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4
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1 answer

Can you call signal() from within a signal handler?

I have a supervisor program that generally wants to receive SIGCHLD events. However, after it receives SIGTERM or similar signal, it would be safe and desirable to ignore SIGCHLD events to prevent zombies. The issue is that I'm not sure if it's…
Benjamin Pollack
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4
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4 answers

How do I receive notification in a bash script when a specific child process terminates?

I wonder if anyone can help with this? I have a bash script. It starts a sub-process which is another gui-based application. The bash script then goes into an interactive mode getting input from the user. This interactive mode continues…
starfry
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3
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1 answer

How to handle SIGHLD

I'm having some troubles using sigchld... what I want to do is to create a child process with fork and make the child print and sleep a second for a couple of times... during these process I want to send signal to child (SIGSTOP and SIGCONTINUED)…
user4334017
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