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Ps ax with grep in loop

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# 1  
Old 07-10-2018
Ps ax with grep in loop
Hello,

I have built the following script to check if processes supplied by the argument are running or not.

Code:
#!/bin/bash

PROCLIST=$1

PROCESS="0"
ERROR_PROCS=""
IFS='+'
read -ra ADDR <<< "$PROCLIST"
for PROC in "${ADDR[@]}"; do
                if [ `ps ax | grep $PROC | grep -v grep | wc -l` -lt 1 ]; then
                PROCESS=1
                ERROR_PROCS="$ERROR_PROCS""$PROC ";
                fi
        done

        if [ $PROCESS -eq 1 ]; then
                echo "CRITICAL - One or more processes ($ERROR_PROCS) not running"
                exit 2
        fi


echo "OK - All monitored processes are running. Process: $PROCLIST"
exit 0

it seems it works fine apart from the fact the "ps ax | grep "process" | wc -l" gives a higher count than expected.
For example, if we take the process named "test" (which doesn't exist), it returns a count of 2.

Code:
[root@matt Linux]# ps ax | grep test | grep -v grep
[root@matt Linux]#

if We run the script with verbose:

Code:
[root@matt Linux]# bash -x ./test2.sh test
+ PROCLIST=test
+ PROCESS=0
+ ERROR_PROCS=
+ IFS=+
+ read -ra ADDR
+ for PROC in '"${ADDR[@]}"'
++ ps ax
++ grep test
++ wc -l
++ grep -v grep
+ '[' 2 -lt 1 ']'
+ '[' 0 -eq 1 ']'
+ echo 'OK - All monitored processes are running. Process: test'
OK - All monitored processes are running. Process: test
+ exit 0

What could be the reason that it captures the value of 2? This also happens if the process does exist. in that case, it returns a 3.

Rgds,

Matthew
# 2  
Old 07-10-2018
Did you consider "false positives"? Processes with the search string as part of the command (fittest, hottest, testcase)? E.g. grep man would show mman, manager on my system.



Any "test" user on the system?
# 3  
Old 07-10-2018
Hi RudiC,

In this case, the test was just used as an example. However, if we still take it for our case then nothing exists as a false positive:

Code:
[root@matt Linux]# ps ax | grep test | grep -v grep
[root@matt Linux]#

in that case that would have returned a value, which means there is nothing related to "test" in our list.

Also if you take an existing process, it will count but adds 2.

Here's another example:

process: master

Code:
[root@matt Linux]# ps ax | grep master | grep -v grep
 1705 ?        Ss     5:42 /usr/libexec/postfix/master -w

So one process exists

if we run the script I have returned a value of 3, 1 for the process 2 not sure why the bash script is originating this number.
I could eventually subtract the value but doesn't make sense.

Code:
[root@am1-stp-oam01 Linux]# bash -x ./test2.sh master
+ PROCLIST=master
+ PROCESS=0
+ ERROR_PROCS=
+ IFS=+
+ read -ra ADDR
+ for PROC in '"${ADDR[@]}"'
++ ps ax
++ grep -v grep
++ wc -l
++ grep master
+ '[' 3 -lt 1 ']'
+ '[' 0 -eq 1 ']'
+ echo 'OK - All monitored processes are running. Process: master'
OK - All monitored processes are running. Process: master
+ exit 0

# 4  
Old 07-10-2018
Strange. I vaguely remember we had a similar problem quite some time ago, but can't find the solution.
For debugging, in the script, echo the variables, and run the ps ax | ... pipe on its own to see its result.


Why, BTW, is above that complicated?
Code:
ps ax -ocomm= | grep -E "${1//+/|}" | sort | comm -13 - <(echo "${1//+/$'\n'}" | sort)

will serve you the non-running processes (of the plus-sign separated list in $1) on a silver plate...
This User Gave Thanks to RudiC For This Post:
nms
# 5  
Old 07-10-2018
Excellent, that really simplifies the job. I have used the one-liner for my benefit as follows:

Code:
#!/bin/bash

PROCLIST=$1
tmp=`ps ax -ocomm= | grep -E "${PROCLIST//+/|}" | sort | comm -13 - <(echo "${PROCLIST//+/$'\n'}" | sort) | wc -l`
tmp2=`ps ax -ocomm= | grep -E "${PROCLIST//+/|}" | sort | comm -13 - <(echo "${PROCLIST//+/$'\n'}" | sort) | tr "\n" " "`

if [ $tmp -gt 0 ]; then
        echo "CRITICAL - One or more processes (`echo $tmp2`) not running"
        else
        echo "OK - All monitored processes are running. Process: `echo $PROCLIST | sed 's/+/,/g'`"
        fi

tmp2 is just to produce them in a one-liner

Thanks again for your feedback
# 6  
Old 07-10-2018
Yes,
Code:
ps ax -ocomm=

does not list users or command arguments, so cannot unwantedly show false positives in them.
Even simpler than
Code:
ps ax -ocomm= | grep "$PROC"

is
Code:
pgrep "$PROC"

Both provide an exit status, so you don't need to count them (with -c option) and compare them.
Code:
if ps ax -ocomm= | grep -q "$PROC"; then echo running; fi

Code:
if pgrep "$PROC" >/dev/null; then echo running; fi

--
Last but not least, you can set IFS='+' temporarily for the read command:
Code:
IFS='+' read -ra ADDR <<< "$PROCLIST"
# continue with the original IFS

This User Gave Thanks to MadeInGermany For This Post:
rbatte1
# 7  
Old 07-10-2018
Why that complicated?
Code:
TMP=$(ps ax -ocomm= | grep -E "${1//+/|}" | sort | comm -13 - <(echo "${1//+/$'\n'}" | sort))
[ $TMP ] && echo "CRITICAL - One or more processes ($TMP) not running" || echo "OK - All monitored processes are running. Process: ${1//+/,}"
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