Check if a program in a specific path is running

Question

I am trying to check if a process is running with the code below:

SERVICE="./yowsup/yowsup-cli"
RESULT=`ps aux | grep $SERVICE`

if [ "${RESULT:-null}" = null ]; then
    echo "not running"
else
    echo "running"
fi

But it keeps echoing it is running although it is not. I realized that the grep itself comes as a result and that is the issue.

How can I skip the grep and just check for the process?

Answer 1

Use pgrep:

if pgrep "$SERVICE" >/dev/null 2>&1 ; then
    echo "$SERVICE is running"
fi

or:

if pgrep -f "/path/to/$SERVICE" >/dev/null 2>&1 ; then
    echo "$SERVICE is running"
fi

NOTE:

• pgrep interprets its argument as a regular expression. As a result, paths containing regex characters will likely fail to match or produce false positives (e.g. pgrep -f /home/user/projects/c++/application/executable won't work as expected due to +). This issue can be worked around by escaping the characters in question (e.g. pgrep -f /home/user/projects/c\+\+/application/executable)

• pgrep -f <pattern> matches the specified pattern against the whole command line of running processes. As a result, it will match paths appearing as arguments of other processes (e.g. run nano /usr/bin/sleep in one terminal and pgrep -f /usr/bin/sleep in another -> pgrep reports the pid of nano since it contains /usr/bin/sleep as an argument in its command line). To prevent these kind of false positives, prefix the pattern with a caret (^) to force pgrep to only match against the beginning of the command line (e.g. pgrep -f ^/usr/bin/sleep)

Answer 2

For systems where pgrep isn't available you can use:

service="[.]/yowsup/yowsup-cli"

if ps aux | grep -q "$service"; then
    echo "not running"
else
    echo "running"
fi

• [.] in will force grep to not list itself as it won't match [.] regex.
• grep -q can be utilized to avoid command substitution step.
• Prefer using lowercase variables in shell.

Answer 3

The problem is that grep you call sometimes finds himself in a ps list, so it is good only when you check it interactively:

$ ps -ef | grep bash
...
myaut    19193  2332  0 17:28 pts/11   00:00:00 /bin/bash
myaut    19853 15963  0 19:10 pts/6    00:00:00 grep --color=auto bash

Easiest way to get it is to use pidof. It accepts both full path and executable name:

service="./yowsup/yowsup-cli" # or service="yowsup-cli"
if pidof "$service" >/dev/null; then
    echo "not running"
else
    echo "running"
fi

There is more powerful version of pidof -- pgrep.

---

However, if you start your program from a script, you may save it's PID to a file:

service="./yowsup/yowsup-cli"
pidfile="./yowsup/yowsup-cli.pid"
service &
pid=$!
echo $pid > $pidfile

And then check it with pgrep:

if pgrep -F "$pidfile" >/dev/null; then
    echo "not running"
else
    echo "running"
fi

This is common technique in /etc/init.d start scripts.

Answer 4

The following solution avoids issues with ps + grep, pgrep and pidof (see Advantages below):

# Check if process is running [$1: path to executable]
function is_process_running() {
    local path="$1" line
    while read -r line; do
        [[ "${line}" == "${path}" || "${line}" == "${path} "* ]] && return 0
    done < <(ps -e -o command=)
    return 1
}

is_process_running "./yowsup/yowsup-cli" && echo "running" || echo "not running"

Explanation:

• ps -e -o command= list all processes, only output command line of each process, omit header line
• while read -r line; do ... done < <(ps ...) process output produced by ps line by line
• [[ "${line}" == "${path}" || "${line}" == "${path} "* ]] check if line matches path exactly -or- path + space + argument(s)

Advantages:

• Works for paths containing regex special characters that would trip grep without option -F or pgrep, e.g. /home/user/projects/c++/application/executable (see NOTE in this answer for details)
• Avoids issues with ps + grep / pgrep reporting false positives if path appears as argument of some other process (e.g. nano /usr/bin/sleep + pgrep -f /usr/bin/sleep -> falsely reports pid of nano process)
• Avoids issues with pidof reporting false positives for processes that are run from PATH (e.g. sleep 60s & + pidof /tmp/sleep -> falsely reports pid of sleep process running from /usr/bin/sleep, regardless of whether /tmp/sleep actually exists or not)

Answer 5

I thought pidof was made for this.

function isrunning()
{
    pidof -s "$1" > /dev/null 2>&1
    status=$?
    if [[ "$status" -eq 0 ]]; then
        echo 1
    else
        echo 0
    fi
)
if [[ $(isrunning bash) -eq 1 ]]; then echo "bash is running"; fi
if [[ $(isrunning foo) -eq 1 ]]; then echo "foo is running"; fi

Answer 6

## bash

## function to check if a process is alive and running:

_isRunning() {
    ps -o comm= -C "$1" 2>/dev/null | grep -x "$1" >/dev/null 2>&1
}

## example 1: checking if "gedit" is running

if _isRunning gedit; then
    echo "gedit is running"
else
    echo "gedit is not running"
fi

## example 2: start lxpanel if it is not there

if ! _isRunning lxpanel; then
    lxpanel &
fi

## or

_isRunning lxpanel || (lxpanel &)

---

Note: pgrep -x lxpanel or pidof lxpanel still reports that lxpanel is running even when it is defunct (zombie); so to get alive-and-running process, we need to use ps and grep

Answer 7

current_pid="$$" # get current pid
# Looking for current pid. Don't save lines either grep or current_pid
isRunning=$(ps -fea | grep -i $current_pid | grep -v -e grep -e $current_pid)

# Check if this script is running
if [[ -n "$isRunning" ]]; then
    echo "This script is already running."
fi

Answer 8

SERVICE="./yowsup/yowsup-cli"
RESULT=`ps aux | grep $SERVICE|grep -v grep`

if [ "${RESULT:-null}" = null ]; then
    echo "not running"
else
    echo "running"
fi