Command executes fine in terminal, not in a bash script

Question

I'm trying:

#!/bin/bash
if $(ps -C "bm_d21_debug")
then
    kill $(ps -C "bm_d21_debug" -o pid=)
    echo "exists"
fi

It returns: "PID: command not found"

Not sure what I'm doing wrong?

You'll want to read the pkill man page. It'll make your life easier. — glenn jackman
– glenn jackman, Commented Feb 23, 2019 at 20:43
It's just weird that if I copy and paste kill $(ps -C "bm_d21_debug" -o pid=) it works fine. but if I copy and paste this whole block, it dies on that line: kill $(ps -C "bm_d21_debug" -o pid= — Penguin
– Penguin, Commented Feb 23, 2019 at 20:46
Shellcheck automatically detects this issue. You can have your editor point them out on the fly. — that other guy
– that other guy, Commented Feb 23, 2019 at 23:37

glenn jackman · Accepted Answer · 2019-02-23 20:54:17Z

3

Consider this line:

if $(ps -C "bm_d21_debug")

You execute the ps command in a command substitution, which returns the command output. The if command then tries to run that output as a command.

The first word of the ps output is PID, which if will handle as the command name. Thus, the "command not found" error.

You just want

if ps -C "bm_d21_debug" >/dev/null; then
    echo running
else
    echo NOT running
fi

answered Feb 23, 2019 at 20:54

glenn jackman

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1 Comment

Penguin Over a year ago

This was my issue. Thanks!

choupit0 · Accepted Answer · 2019-02-23 20:32:19Z

0

I suggest to use square brackets also:

if [[ $(ps -C "bm_d21_debug") ]]

But this command will always return "yes" ($? = 0)

answered Feb 23, 2019 at 20:32

choupit0

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1 Comment

Penguin Over a year ago

Square brackets scare me, but I fixed it by changing to this code: stackoverflow.com/a/54846069/11107107 Thanks!

Penguin · Accepted Answer · 2019-02-23 20:48:19Z

0

Fixed by changing to

if ps aux | grep ./bm_d21_debug | grep -v grep >/dev/null;then
    pid=$(ps aux | grep ./bm_d21_debug | grep -v grep | awk '{print $2}')
    kill $pid
    echo $pid
fi

answered Feb 23, 2019 at 20:48

Penguin

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