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

learn more… | top users | synonyms

2
votes
2answers
85 views

gracefully terminating processes with killall <processname>

I am using several instances (profiles) of Icedove (Thunderbird) and when I need to close all of them, I use: killall icedove According to man killall, if no signal name is specified, SIGTERM is ...
0
votes
1answer
20 views

Trying to see default handlers for various signals

I understand that there is a default signal handler, that is a function for each signal , such as SIGKILL etc. In which file it is written? I tried looking at signal.h, but could not find it there. ...
2
votes
1answer
35 views

How to suspend a process for a certain period of time?

I have several running processes which is started by a shell, but I don't want them to run during 08:00am - 20:00pm for each day because they are really bandwidth-consuming, so , I have to suspend ...
1
vote
2answers
27 views

Give group the right to send kill signals

I have a process that a user1 runs. And I need to grant all the group members the right to send some kill signal to it. So far, I always get this output: myProcess(13919): Operation not permitted ...
0
votes
0answers
15 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 ...
2
votes
1answer
24 views

SIGTERM not working occasionally

We use the regular /etc/init.d/jboss stop to stop the jboss on our machines. But at times, it does not stop the process and we get what is pasted below. When this happens we kill the process with a ...
2
votes
2answers
29 views

Inheriting Bash signal traps

I'm struggling to find clear, unambiguous information about how the trap command works. In particular, is the effect of trap local to the script where it appears? I had always assumed this to be the ...
1
vote
0answers
25 views

How to propagate TSTP while running a program as a different user

I'm running a terminal application via "su" in this fashion: su -c "/path/to/app --args" username This is done from a root context, and 'username' is a less privileged user in the system. The ...
1
vote
1answer
32 views

On shutdown, do un-mounting drives happen before shutdown signal handling?

So based on my understanding of the Unix/Linux shutdown process (which is highly limited I admit), I think at some point these steps happen: 1. mounted drives get unmounted 2. a termination signal ...
1
vote
1answer
37 views

Change to rc.local causing hang on tty1

I added a script execution command to my rc.local but forgot to run it in a separate tty. The script has an infinite loop and has hung my tty1. Ctrl-C does not do anything and I don't have another ...
5
votes
1answer
75 views

Why different behaviour of trapping EXIT vs INT

Running bash 4.3 on Kubuntu Trusty 64 bit. Please see the following two files: trapping-int.sh #! /bin/bash trap "echo Exiting" INT cat </dev/urandom >/dev/null echo Hello trapping-exit.sh ...
1
vote
1answer
69 views

Start a background process from a script and manage it when the script ends

I'd like to run and configure a process similarly to a daemon from a script. My shell is zsh emulated under Cygwin and the daemon is SFK, a basic FTP server. For what matters here, the script ...
3
votes
3answers
68 views

Control which process gets cancelled by Ctrl+C

I have a live CD that boots into Linux and runs a small Bash script. The script searches for and runs a second program (which is usually a compiled C++ binary). You're supposed to be able to abort ...
1
vote
1answer
31 views

What is the meaning of every column when executing psig command?

I try to use psig command to track signal dispositions of a process on Solaris: bash-3.2# psig 3109 3109: bash HUP caught termsig_sighandler 0 ...
1
vote
1answer
124 views

What does the command pkill -USR1 -n -x dd mean exactly?

I am using dd to do a network transfer of a disk image to an sd card on my BeagleBone. Using pkill -USR1 -n -x dd in an ssh connection to this BeagleBone gives me a status update of the transfer ...
3
votes
0answers
60 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 ...
3
votes
1answer
43 views

Terminating SSH called from a script (SIGPIPE handling?)

so I was wondering why there are some hanging SSH connection left from some of my automated scripts and I came to a weird issue - SSH, if used without PTY, doesn't terminate when the output pipe gets ...
2
votes
1answer
61 views

How to restore the default signal processing behavior on Solaris?

I have found the signal processing behavior on my Solaris 10 is changed. For example, when I Ctrl+C, the program can't exit. Use psig to check the signal processing behavior: HUP default INT ...
2
votes
1answer
158 views

Prevent SIGINT from interrupting function call and child process(es) within

Consider the following script: #!/bin/bash set -o pipefail set -o history trapper() { func="$1" ; shift for sig ; do trap "$func $sig" "$sig" done } err_handler () { case $2 in ...
16
votes
2answers
1k views

Why does `kill -l` not list signal numbers of 32 and 33?

Executing kill -l on linux gives: 1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV ...
1
vote
1answer
63 views

Send specific signal number with specific key

I want to set a specific key like F12 to send me a specific signal number that out of linux signals range that I can handle this signal with trap command. How can I do that? NOTE: I'm working with ...
4
votes
1answer
103 views

How to catch a signal in command line?

I asked this question. SIGPIPE signal is generated to stop the execution of the command as told in the answer. But how do I capture this signal and gracefully terminate the command? The command exits ...
1
vote
1answer
35 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 ...
2
votes
0answers
25 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. ...
0
votes
0answers
23 views

Show signals received by processes [duplicate]

Is there a command or file that stores what signals each process receives? I know if I open one from a terminal and kill -9 PID it'll tell me, but what about something like firefox that is opened ...
1
vote
2answers
58 views

What happens to the signals requested recursively?

People often hit Ctrl + c or Ctrl + z to cancel or abandon the job if the process gets sluggish, in this case which of these signals get processed, the first one or the last one? is each signal ...
3
votes
2answers
71 views

Why is my trap not printing any log message?

What I'm doing is, trap 'rm -f /path/of/file/fileName.running; echo "TRAPPED & READY";' 1 2 9 15 >> trap.log I didn't get anything in log & the file which should have been deleted ...
9
votes
4answers
3k views

Why is SIGINT not propagated to childs process when sent to it's parent process?

Given a shell process (e.g. sh) and it's child process (e.g. cat), how to simulate the behavior of CTRL+C using the shell's process ID? This is what I've tried: Running sh and then cat: ...
2
votes
1answer
22 views

Multiple processes reporting signals received

If I run multiple programs with program & in one terminal, and then from another one start sending SIGKILL SIGINT or any other signal, will the terminal running all the processes tell me what ...
1
vote
1answer
50 views

Can Linux programs be sent a SIGXXX command they can respond to in the UI?

I am trying out the timeout command and would like to know if there is a kill signal that a GUI program, whether a graphics desktop or a terminal program will treat as the user terminating the program ...
2
votes
1answer
577 views

Forward SIGTERM to child in Bash

I have a Bash script, which looks similar to this: #!/bin/bash echo "Doing some initial work...."; /bin/start/main/server --nodaemon Now if the bash shell running the script receives a SIGTERM ...
1
vote
0answers
85 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 ...
0
votes
3answers
57 views

Idiomatic way to kill -9 only if “graceful” way doesn't work?

Is there a common way or existing utility to do the following? kill a process Give it a few seconds to shut down gracefully kill -9 it if it hasn't stopped
4
votes
2answers
114 views

How to programatically detect when a device raises an interrupt?

How to programatically detect when a device raises an interrupt? This can be when a device is connected or disconnected. And also this case: for example: when a finger is held over a fingerprint ...
5
votes
1answer
50 views

Ctrl-C is ignored by pppd when put in a shell script

I'm trying to connect to GPRS network through a serial port connected GSM modem. When I call /usr/sbin/pppd call <peer_name> from the command line, it correctly receives and handles Ctrl+C from ...
1
vote
1answer
32 views

How do I obtain the kill signal / message / reason within a script?

I am using the following trap: trap OnExit EXIT And in my OnExit function I would like to capture all the info I can on what happened so I can write it to a log file. Id like to know who, why, how, ...
2
votes
1answer
55 views

What signal does X send to its clients when it receives SIGINT?

If I terminate the Xorg server with a SIGINT signal (eg. when I press Ctrl+C), what signal does it send to its clients?
2
votes
1answer
67 views

Does this dispatcher produce zombie process?

I have such a dispatcher shell script. while read line do java TestProg $line & done < $tasklist On the zombie process Wikipedia page, it says if a parent fails to call wait, the ...
3
votes
1answer
115 views

SIGKILLing after a grace period

I've seen a lot of process managers that try to do this. It was my understanding that you should only use SIGTERM to kill a process. The process could take an unknown amount of time to clean up after ...
0
votes
0answers
34 views

Execute snippet of code when key is pressed [duplicate]

I want to create a process in Linux which waits for some particular keys to be pressed and executes a snippet of code and goes back to sleep. How can I achieve this? Initially a process will be in ...
3
votes
1answer
2k views

ctrl c vs. ctrl z with foreground job

Ctrl+Z stops the job whereas Ctrl+C kills the job. Why is that? Wouldn't the other way make more sense? z@z-lap:~$ sleep 100& [1] 4458 z@z-lap:~$ sleep 200& [2] 4459 z@z-lap:~$ jobs [1]- ...
8
votes
1answer
422 views

stderr over ssh -t

This sends output to STDERR, but does not propagate Ctrl+C (i.e. Ctrl+C will kill ssh but not the remote sleep): $ ssh localhost 'sleep 100;echo foo ">&2"' This propagates Ctrl+C (i.e. ...
12
votes
2answers
1k views

How to terminate remotely called “tail -f” when connection is closed?

I just noticed that if I execute ssh user@remote_host tail -f /some/file , then tail -f /some/file keeps running on the remote_host even if ssh connection is closed! So, after several connects and ...
0
votes
0answers
363 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 ...
2
votes
3answers
189 views

CTRL C behavior in hierarchy of shells

First of all sorry about terminology errors, I'd try to be clear. I open a shell (like sbt or node debug from my bash). Then inside this shell, I open another one (using scala or node repl ...
3
votes
5answers
1k views

Getting pid of bash script from itself

I have a bash script with doing lot of things called script.sh: #!/bin/bash #It #Is #Doing #Things Is there a way that I be able to get the proccess of script and then kill it after 5 minutes? ...
0
votes
2answers
329 views

Disable the display of “terminated xxx” info of bash

For example, when I kill a background process, then bash weil display terminated xxx, How to disable this info? $ ping g.cn >/dev/null & [1] 25123 $ pkill ping [1] + 25123 terminated ping ...
2
votes
1answer
99 views

calling sigprocmask from bash

I have a process that spawn a bash command with system() while the signal mask has all the signals blocked. This cannot be fixed easily. The bash command eventually execs into a process. The all ...
2
votes
2answers
36 views

Does time window still exist when the signal is not blocked

Many books say that a time window exists between the generation and delivery of the signal when the signal is not blocked. So I wonder whether the time window still exists when the signal is not ...
2
votes
2answers
216 views

Bash script to signal a concurrently running instance (same script) about a condition and increment counter

Background Here's what I want to achieve. I have a (potentially) long-running process. Now I have locking in place just fine and all is generally in order. However, since this is a scheduled job, ...