问题
I use iptraf to monitor the network traffic in linux, and the shell command is(make iptraf running in background):
iptraf -s eth0 -f -B -L ./traffic.dat
if I want to get the result, I have to stop iptraf first, so I use the shell command:
kill -SIGUSR2 $pid
however, I could not stop iptraf if I move these shell commands into a bash script file(net.sh), and I get an error:
kill: SIGUSR2: invalid signal specification
I use 'kill -l' in the script file(net.sh), and I find there is no parameter which name is SIGUSR2. and I would get nothing if I use USR2 or -9.
the complete script file is:
iptraf -s eth0 -f -B -L ./temp.txt
pid=`ps -ef | grep iptraf | grep -v grep | awk '{print $2}'`
kill -USR2 $pid
cat temp.txt
I get nothing after these commands.
what shoud I do if I want to get the result?
回答1:
SIGUSR2 is architecture depended and can have a value out of 31, 12 or 17. This is described in man 7 signal. You'll have to find out which value is appropriate for your system. Usually this is done by having a look into:
/usr/include/asm/signal.h
On my system - Ubuntu 12.04 AMD 64 - it has a value of 12:
#define SIGUSR2 12
Once you know the proper numeric value for SIGUSR2 on your system, you can send this signal using:
kill -SIGNO PID
# In this case
kill -12 PID
回答2:
On my Linux box it works.
I ran an infinite loop (pid = 4574), then I ran
#!/bin/bash
kill -l | grep USR2
kill -SIGUSR2 4574
kill -l has showed the signal and kill -SIGUSR2 has sent the signal (killing the process).
Check if you are running Bash or some other shell (e.g., dash, busybox, etc.)
回答3:
The Posix'y way to do this is by using -s without the SIG prefix. E.g.,:
kill -s USR2 $pid
This seems to work on both MacOS and linux.
来源：https://stackoverflow.com/questions/17588767/how-to-use-kill-sigusr2-in-bash