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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274 views

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
91 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
69 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 ...
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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
36 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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0answers
187 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
30 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
67 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 ...
2
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0answers
67 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
128 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
20 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
20 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
66 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 ...
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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
242 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
205 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
460 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 ...
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0answers
8 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
19 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
35 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
42 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 ...