Ubuntu Bash Script executing a command with spaces

Question

I have a bit of an issue and i've tried several ways to fix this but i can't seem to.

So i have two shell scripts.

background.sh: This runs a given command in the background and redirect's output.

#!/bin/bash

if test -t 1; then
  exec 1>/dev/null
fi

if test -t 2; then
  exec 2>/dev/null
fi

"$@" &

main.sh: This file simply starts the emulator (genymotion) as a background process.

#!/bin/bash
GENY_DIR="/home/user/Documents/MyScript/watchdog/genymotion"
BK="$GENY_DIR/background.sh"
DEVICE="164e959b-0e15-443f-b1fd-26d101edb4a5"
CMD="$BK player --vm-name $DEVICE"
$CMD

This works fine when i have NO spaces in my directory. However, when i try to do: GENY_DIR="home/user/Documents/My Script/watchdog/genymotion"

which i have no choice at the moment. I get an error saying that the file or directory cannot be found. I tried to put "$CMD" in quote but it didn't work.

You can test this by trying to run anything as a background process, doesn't have to be an emulator.

Any advice or feedback would be appreciated. I also tried to do.

BK="'$BK'"

or

BK="\"$BK\""

or

BK=$( echo "$BK" | sed 's/ /\\ /g' )

Your directory which might have empty spaces is assigned to your GENY_DIR variable so I'd think when you quote CMD it has no effect. Have you tried to quote your ${GENY_DIR} and see how it behaved ? — ODelibalta
– ODelibalta, Commented Jul 22, 2016 at 20:59
Thanks guys, storing it in an array as suggested by @that other guy worked like a charm :) — codeCompiler77
– codeCompiler77, Commented Jul 22, 2016 at 21:26

that other guy · Accepted Answer · 2016-07-22 21:58:09Z

4

Don't try to store commands in strings. Use arrays instead:

#!/bin/bash
GENY_DIR="$HOME/Documents/My Script/watchdog/genymotion"
BK="$GENY_DIR/background.sh"
DEVICE="164e959b-0e15-443f-b1fd-26d101edb4a5"
CMD=( "$BK" "player" --vm-name "$DEVICE" )
"${CMD[@]}"

Arrays properly preserve your word boundaries, so that one argument with spaces remains one argument with spaces.

Due to the way word splitting works, adding a literal backslash in front of or quotes around the space will not have a useful effect.

John1024 suggests a good source for additional reading: I'm trying to put a command in a variable, but the complex cases always fail!

edited Jul 22, 2016 at 21:58

answered Jul 22, 2016 at 21:00

that other guy

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7 Comments

codeCompiler77 Over a year ago

./main.sh: line 5: 'home/user/Documents/My Script/watchdog/genymotion/background.sh': No such file or directory is the error message returned when trying to run as an array. I confirmed that the file exists :)

that other guy Over a year ago

I copied your code, I don't know where your files are. Are you sure there wasn't supposed to be a / in front of that?

codeCompiler77 Over a year ago

Yes sorry, there is a / in front of home, i use the $HOME variable but i typed it out for this.

that other guy Over a year ago

Ok. It's tricky to debug by proxy when you're running one version and posting another. What is the actual error message? The error you posted said line 5, but that would not happen on line 5 as posted in this solution.

John1024 Over a year ago

+1. Also, for good background reading on this, see: "I'm trying to put a command in a variable, but the complex cases always fail!"

|

Jamie Le Tual · Accepted Answer · 2016-07-22 21:04:49Z

-2

try this:

GENY_DIR="home/user/Documents/My\ Script/watchdog/genymotion"

You can escape the space with a backslash.

answered Jul 22, 2016 at 21:04

Jamie Le Tual

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1 Comment

codeCompiler77 Over a year ago

./main.sh: line 5: '/home/user/Documents/My\: No such file or directory

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