A signal is a message which can be sent to a running process. Signals can be initiated by programs, users, or administrators.

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Cannot rewrite “trap command” for SIGTSTP, SIGTTIN and SIGTTOU

I want to trap the SIGTSTP signal, but I'm not able to. When I call just trap command without arguments, I'm getting this: trap -- '' SIGTSTP trap -- '' SIGTTIN trap -- '' SIGTTOU Obviously, my ...
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1answer
60 views

Parent restarted by child doesn't respond to CTRL-C

I wrote a program. It starts a process (call it A) that spawns a child process (call it D) that shutdowns and restarts A. Problem is, now I can't kill A nicely from the terminal (ie. CTRL-C isn't ...
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1answer
139 views

Bash shell launched by forkpty() spawns child processes that ignore SIGINT. Why and how do I ensure SIGINT is not ignored?

I have a C program that uses forkpty to execute a bash shell. I'm finding that the programs launched by this shell are launched with SIGINT ignored, so when I send a Ctrl-C to the shell they never ...
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1answer
79 views

SIGINT handling differences between bash 3 and 4

I have a script which works great in bash 4.3, but gives me unexpected behavior with bash 3.2. Here's a simplified version: set -o errexit -o pipefail task() { local name=${1} local duration=...
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1answer
75 views

PID of process causing error

I have this script: #!/bin/bash # -> dump.$pid ulimit -c unlimited # trap ERR set -o errexit # also trap error in the middle of a pipe (1) # otherwise it will only trap the error on (2) set -o ...
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1answer
90 views

How does one establish SIGRTMIN at run-time?

Reading up on signal(7) I can see that now: two, but once: three; signal numbers past 31 are reserved for use by the Real-time signal system and should not be used: Real-time Signals Linux ...
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31 views

Linux application development and signal handling

Currently I am having problems with my users complaining about the termination of my application. Under some (seemingly arbitrary) conditions and desktop environments the app is not terminated and ...
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0answers
197 views

Kill a whole process tree regardless different GIDs

I am having issues with process control using the signals available to the process abstraction. In the example below you can see there is a perl script which is the parent of the whole tree with a ...
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0answers
38 views

Why does pacman stop when I freeze the output with ctrl+s

I sometimes use ctrl+s to send an XOFF signal to freeze the output of a program without stopping the program itself. However, pacman, unlike most other programs, stops as if you had pressed ctrl+z. It ...
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0answers
72 views

What signal is sent when you close a bash terminal to the programs it was running

I have a bash script that launches a python program. The bash script handles SIGINT SIGTERM and SIGHUP signals to do a cleanup operation. I noticed that when I close the process in a tab in LXTerminal,...
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0answers
325 views

What happens to a multithreaded Linux process if it gets a signal?

If a Unix (Posix) process receives a signal, a signal handler will run. What will happen to it in a multithreaded process? Which thread receives the signal? On my opinion, the signal API should be ...
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0answers
73 views

unbuffer/expect swallows the rcode when its child is signaled

unbuffer is able to pass along the return code of a process under normal circumstance, but if the process you are unbuffering is killed, for instance with a segfault, I see $? as 0 while I expect 139. ...
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0answers
472 views

Why does this pipeline get SIGTTIN?

When I run the command for i in *.log; do cat "$i" | sort; done | more, the pipeline gets a SIGTTIN signal and is stopped. bash$ for i in *.log; do cat "$i" | sort; done | more ### (one screenful of ...
2
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0answers
130 views

Busybox exits instantly printing 'SIGUSR1'

I was tinkering with my router these days. It runs on MIPS core and the OS is based on Linux. But the builtin busybox is very limited. I managed to export a binary of busybox compiled for MIPS through ...
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0answers
19 views

Trap ctrl c not working as expected

I have a code that looks like this: { trap cleanup SIGHUP SIGINT SIGTERM function executed() { if [ ${1} -ne 0 ] then echo "Failed!" cleanup ...
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0answers
22 views

killing subprocesses and traps

I have the following two scripts which simulate some work: start.sh simply launches 2 (mpi) processes with script mpiproc.sh. start.sh #!/bin/bash function trap_with_arg() { func="$1" ; shift ...
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0answers
22 views

How do I escalate a signal?

For the past week, I been having a bug that my python code hasn't been doing a cleanup process properly. It was suppose to once it captures a signal caused by closing the terminal, it does some ...
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0answers
74 views

CentOS Running process not responding to kill signals and not context switched

An updatedb process on my linux server is not responding to kill signals. (kill -9 or SIGSTOP) [root@chroot-1 ~]# ps auwx | grep -i 4505 root 4505 99.5 0.0 59544 1256 ? RN 09:43 112:...
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0answers
15 views

How do I terminate Aptitude safely

I have a TMux session with Aptitude open. The Aptitude process has been "killed" several times with STOP/CONT. Now it doesn't react to the Q key. Instead a 'q' is printed on the top-left corner of the ...
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0answers
214 views

Trap not trapping SIGTSTP

I have a script that keeps displaying the login prompt: #!/bin/bash trap '' 2 20 while true; do login done This is part of a bigger project so please don't tell me to just use the system login ...
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0answers
38 views

Fixing Signal 13 Error on find

I have a situation where I'm trying to install softwares into my system. I'm using a fakeroot approach to install them in a separate directory where I'm listing all the files, directories and links ...
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0answers
17 views

What is the difference between the SIGHUP generated by typing “exit” in the SSH shell terminal vs clicking the “X” button in the PuTTY window?

Referring to this question, I am trying to use nohup <command> <arg> & to continue to run a command in the background after I logout from the SSH shell terminal. However, the ...
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0answers
21 views

Program is not launcher in function that is called by a signal trap

I have a bash script that requires some cleanup commands to happens when it gets closed in the console. Basically the cleanup is a restart command in my python deamon progarm (Lets call this P), ...
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0answers
38 views

How often is SIGHUP called in this situation?

I have situation where I am connected to my BeagleBone Black over USB cable, and I started my application in Linux terminal and I'm watching its execution, it sends me some data to terminal and it ...
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0answers
47 views

Sigstop when trying to run script?

I am trying to list out all commands by users, unfortunately I hit a weird sigstop that I am not sure how to diagnose? #!/bin/ksh echo '[' for USER in `cut -d: -f1 /etc/passwd |sed '/^#/ d'`; do ...
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0answers
2k views

Archive (Compress) giant folder in Linux using command line without termination

Well, I'm just trying to compress a whole directory (infact giant!) under Linux using a terminal. The entire folder size is about 7 GB. I've used below command to create the archive. tar -zcvf ...