I have a simple script as below which checks if fail2ban service is running or not on Ubuntu 18.04:

#!/bin/bash
# Script to check if fail2ban service is running
if pgrep -x "fail2ban" > /dev/null
then echo "Fail2ban is running"
else echo "Fail2ban is not running"
fi

I have installed fail2ban in a test VM and is running on the VM. Here is a screenshot of systemctl status command.

But, when the run the above script, I get the result that "Fail2ban is not running". I am not sure if is with the script. I tried ps aux command too instead of pgrep. But, I still get the same result.

5

2 Answers

You asked pgrep to exactly (-x) search for a process called fail2banbut the output of systemctl status shows it is called /usr/bin/python3 instead.

To check whether a systemd unit is running use

systemctl is-active --quiet fail2ban

That is:

if systemctl is-active --quiet fail2ban; then echo "running"
else echo "not running"
fi

3

The following shellscript running combines the result of

• systemctl is-active and
• ps -ef | ... | grep

in order to detect if a certain program (or a program name containing the search string) is running or not.

#!/bin/bash
if [ $# -ne 1 ]
then echo "Usage: $0 <program-name> $0 <part of program name>
Examples: $0 firefox $0 term $0 dbus $0 'dbus-daemon --session'" exit
fi
inversvid="\0033[7m"
resetvid="\0033[0m"
redback="\0033[1;37;41m"
greenback="\0033[1;37;42m"
blueback="\0033[1;37;44m"
runn=false
tmpfil=$(mktemp)
# check by systemctl
systemctl is-active --quiet "$1"
if [ $? -eq 0 ]
then echo "systemctl is-active:" runn=true
fi
# check by ps
ps -ef | tr -s ' ' ' ' | cut -d ' ' -f 8-9 | grep "$1" | grep -vE -e "$0 $1" -e "grep $1" | sort -u > "$tmpfil"
tmpstr=$(head -n1 $tmpfil)
#echo "$tmpstr"
if [ "$tmpstr" == "$1" ] || [ "${tmpstr##*/}" == "$1" ] || [ "${1##*/}" == "${0##*/}" ]
then echo "ps -ef: active:" runn=true
elif test -s "$tmpfil"
then if $runn then echo "----- consider also ---------------------------------------------" cat "$tmpfil" echo "-----------------------------------------------------------------" else echo "----- try with: -------------------------------------------------" cat "$tmpfil" echo "-----------------------------------------------------------------" fi
fi
if $runn
then echo -e "$greenback $1 is running $resetvid"
else inpath=$(which "$1") if [ "$inpath" == "" ] then echo -e "$redback no path found to $1 $resetvid" else echo -e "$blueback $1 is not running $resetvid" fi
fi

Make it executable and put it in a directory in PATH, if you wish. I put it into my bin directory and can used it without any path.

Usage:

$ running
Usage: /home/sudodus/bin/running <program-name> /home/sudodus/bin/running <part of program name>
Examples: /home/sudodus/bin/running firefox /home/sudodus/bin/running term /home/sudodus/bin/running dbus /home/sudodus/bin/running 'dbus-daemon --session'

Examples:

$ running firefox
ps -ef: active: firefox is running # green background - running
$ running term
----- try with: -------------------------------------------------
/usr/lib/gnome-terminal/gnome-terminal-server
xterm
x-terminal-emulator
----------------------------------------------------------------- no path found to term # red background - path not found
$ running dbus
systemctl is-active:
----- consider also ---------------------------------------------
/usr/bin/dbus-daemon --session
/usr/bin/dbus-daemon --syslog
/usr/bin/dbus-daemon --system
/usr/bin/fcitx-dbus-watcher unix:abstract=/tmp/dbus-Nm2MSvuTZF,guid=25bad8d51276d088045625055c425080
----------------------------------------------------------------- dbus is running # green background
$ running 'dbus-daemon --session'
ps -ef: active: dbus-daemon --session is running # green background
$ running libreoffice libreoffice is not running # blue background - not running

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