different count using ps and wc to check if service is running in bash

Question

I have a small script to check if a service is running in bash

#!/bin/bash

countlines=""$(ps -ef | grep netdata | grep -v grep | wc -l)

echo $countlines >> mylog.log

if [ ${countlines} -lt 3 ];then

sudo /bin/systemctl restart netdata

fi

The problem is when I issue a ps -ef | grep netdata | grep -v grep | wc -l at the command line the result is always 3 but mylog.log is:

[update: added filtered ps -ef results]

forge@reportserver:~ ps -ef | grep netdata
netdata  22308     1  0 08:38 ?        00:00:37 /usr/sbin/netdata -D
netdata  22386 22308  0 08:38 ?        00:00:58 /usr/libexec/netdata/plugins.d/apps.plugin 1
netdata  47045 22308  0 11:38 ?        00:00:02 bash /usr/libexec/netdata/plugins.d/tc-qos-helper.sh 1
forge    52028 27902  0 12:34 pts/8    00:00:00 grep --color=auto netdata

why such a discordance?

@Mahdia the problem is that OP got `3` in their command, but `6` in their log file — Aserre, Jul 25 '17 at 07:14
This: `countlines=""$(ps -ef | grep netdata | grep -v grep | wc -l)` can be resumed to: `countlines=$(ps -ef | grep -c netdat[a])` — Juan Diego Godoy Robles, Jul 25 '17 at 07:19
The combination of `ps` and `grep` is called [`pgrep`](https://en.wikipedia.org/wiki/Pgrep). — ceving, Jul 25 '17 at 09:51
that is @Mahdia, the issue is the different count, not the append. Changed question to clear it up — Forge, Jul 25 '17 at 09:55
I ran your code and it works well.Can you post output of `ps -ef`? — Mahdi, Jul 25 '17 at 10:05

score 0 · Answer 1 · answered Jul 25 '17 at 07:15

0

split into 2 commands to see why:

ps_grep_output=$(ps -ef | grep netdata | grep -v grep)

echo "$ps_grep_output" >> mylog.log

countlines=$(wc -l <<< "$ps_grep_output")

echo "$countlines" >> mylog.log

answered Jul 25 '17 at 07:15

Nahuel Fouilleul

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same results with your suggestion @Nahuel – Forge Jul 25 '17 at 10:01
could you see which lines are differing when executing from command line – Nahuel Fouilleul Jul 25 '17 at 10:31
all of them Nahuel – Forge Jul 26 '17 at 08:45

different count using ps and wc to check if service is running in bash

1 Answers1