Shell Scripting Questions, Writing alarm clock script

burgsprinta · 11-27-2010, 04:54 PM

I left the linux world for a few years and now i am trying to re-learn my shell scripting basics. I am writing a script for an alarm clock, but i seem to be running into a few issues. My script is posted below. If anyone could help, that would be great. Thanks.

------------------------------------------------------------
#!/bin/bash
declare -i H
declare -i M
declare -i currentH
declare -i currentM
declare -i minutesLeft
declare -i hoursLeft
echo -e "What Hour (24 Format) do you want to Wake Up?"
read H
echo -e "What Minute?"
read M
echo `expr $H + 0`
currentH=`date +%H`
currentM=`date +%M`
echo "You Selected "
echo "$H:$M"
echo -e "\nIt is Currently $currentH:$currentM"

if [ "$currentH" < "echo $H" ];
then
hoursLeft= `expr $H - $currentH`
echo "$H - $currentH means You Have: $hoursLeft hours still"
fi

if [ "$currentH" > "$H" ]; then
hoursLeft= `expr $currentH - $H`
echo -e "\n$currentH - $H means you have $hoursLeft hours left \n"
fi

if [ "$currentH" == "$H" ]; then
hoursLeft= 0
echo -e "Taking a nap?\n"
fi

if [ "$currentM" < "$M" ];
then
minutesLeft= `expr $M - $currentM`
echo -e "$M -$currentM menas you have: $minutesLeft minutes still"
fi

----------------------------------

My script, instead of doing what it should, produces the following errors:

./alarm: line 19: echo 11: No such file or directory
./alarm: line 26: 6: command not found

17 - 11 means you have hours left

./alarm: line 37: -41: command not found
11 -52 menas you have: minutes still
expr: non-integer argument
52 - 11 means you have 0 minutes left

Sleeping... for hours and 0 minutes

sleep: invalid time interval `h'
Try `sleep --help' for more information.

and if i choose the time 11:06, files called 11 and 6 are creating in the working directory. I am sure it is something really simple, but i haven't used linux or scripting on my computers in around 6 years. Thanks.

AlucardZero · 11-27-2010, 04:59 PM

Code:

if [ "$currentH" < "echo $H" ];

What are you trying to do here?

If you're comparing whether the current hour value is less than the alarm hour, then the "echo " makes no sense.

Could you repost your code at http://pastebin.com/ (select Bash) so we can have line numbers, monospacing, and syntax highlighting?

burgsprinta · 11-27-2010, 05:05 PM

Yes the echo does not make sense. Sorry about that. That actually should have been cleaned up, but I deleted it from my script, but forgot to delete it from here.

Thanks for the quick response.

GrapefruiTgirl · 11-27-2010, 05:07 PM

Here's a few tips to get you further along:

1) When comparing integers, do it like this:

Code:

if [ $H -gt 3 ]; then

Notice no quotations around the variable and the 3. When you use quotations, it should be for strings. -gt means "greater than", but there are other for less-than, equals, etc.. See bash man page for more on this.

2) When assigning values to vaiables, make sure there's no space after the "=" sign:

Code:

hoursLeft= `expr $H - $currentH`
          ^^

3) What does this do:

Code:

echo `expr $H + 0`

I mean, I know it supposed to echo something, but why? Just curious.... And for what it's worth, a bit less clunky way of doing simple math is like this, without expr:

Code:

echo $((VAR + 5))
echo $((VAR - OTHER_VAR))

Anyhow, check out that stuff and fix up your code a little. Then re-post the updated version for us in your next post. Please use code tags around your script ( see here: http://www.phpbb.com/community/faq.php?mode=bbcode#f2r1 )

Cheers.

burgsprinta · 11-27-2010, 05:09 PM

Quote:

Originally Posted by AlucardZero

Code:

if [ "$currentH" < "echo $H" ];

What are you trying to do here?

If you're comparing whether the current hour value is less than the alarm hour, then the "echo " makes no sense.

Could you repost your code at http://pastebin.com/ (select Bash) so we can have line numbers, monospacing, and syntax highlighting?

I am trying to set an alarm. I am going to add a command to invoke mplayer at the given time after the sleep commands, but this is more than anything just me trying to get back into scripting. Kind of frustrating, because I used to be able to do kind of task fairly easily. Somehow I completely forgot almost everything.

Posted to
http://pastebin.com/TMH7qtXk

Thanks

burgsprinta · 11-27-2010, 05:21 PM

Thanks AlucardZero and GrapefruiTgirl. Fixed it now. Runs well now. Here is the new code:

Code:

#!/bin/bash
declare -i H
declare -i M
declare -i currentH
declare -i currentM
declare -i minutesLeft
declare -i hoursLeft
echo -e "What Hour (24 Format) do you want to Wake Up?"
read H
echo -e "What Minute?"
read  M
currentH=`date +%H`
currentM=`date +%M`
echo "You Selected "
echo "$H:$M"
echo -e "\nIt is Currently $currentH:$currentM"

if [  $currentH -lt $H ];
        then
                hoursLeft=`expr $H - $currentH`
                echo "$H - $currentH means You Have: $hoursLeft hours still"
fi

if [ $currentH -gt $H ]; then
        hoursLeft=`expr $currentH - $H`
        echo -e  "\n$currentH - $H means you have $hoursLeft hours left \n"
fi

if [ $currentH == $H ]; then
        hoursLeft=0
        echo -e "Taking a nap?\n"
fi

if [ $currentM -lt $M ];
        then
                minutesLeft=`expr $M - $currentM`
                echo -e "$M -$currentM menas you have: $minutesLeft minutes still"
fi

if [ $currentM -gt $M ]; then

        minutesLeft=`expr $currentM - $M`
        echo -e "$currentM - $M means you have $minutesLeft minutes left \n"
fi

if [ $currentM == $M ]; then
        minutesLeft=0
        echo -e "and no minutes\n"
fi

echo -e "Sleeping... for $hoursLeft hours and $minutesLeft minutes \n"
sleep $hoursLeft\h
sleep $minutesLeft\m
mplayer ~/.alarm/alarm.mp3

Thanks everyone. Responses were quick and helpful.

burgsprinta · 11-27-2010, 05:24 PM

Is it necessary for me to declare the variables as integers?

GrapefruiTgirl · 11-27-2010, 05:33 PM

Quote:

Originally Posted by burgsprinta

Is it necessary for me to declare the variables as integers?

Not really, no. There must be a good reason that `declare` exists, (and actually I saw a recent example where it HAD to be used to define an array before using it) but I virtually never declare integers in any scripts I write. Doesn't seem to matter. The bash man page says:

Code:

A shell variable need not have its integer attribute turned on to be used in an expression.

So that's good for me. Someone else may have other thoughts on this...

GrapefruiTgirl · 11-27-2010, 05:39 PM

However! I should add that, something to keep in mind is that: if you're doing integer comparisons with variables, and one or another variable that has not been given a value (or zero), but you expect it to have an integer (not a string) then you can get errors. Like so:

Code:

root@reactor: [ $c -eq 3 ] && echo "equal"
bash: [: -eq: unary operator expected

I had not set the variable $c to anything at all, so the error results. If I had set an integer value to $c there would be no error. Using `declare` beforehand, does not prevent this.

burgsprinta · 11-27-2010, 06:00 PM

So i should set my integer variables equal to a non-zero number first? Thanks. The last code i posted doesn't work under all circumstances, but now that I have the very basics worked out, it shouldn't be too difficult. Thanks so much.

GrapefruiTgirl · 11-27-2010, 06:06 PM

Well, take for example the following simple script:

Code:

#!/bin/bash

NAME="bob"

if [ "$NAME" = "fred" ]; then
        c=5
fi

if [ $c -eq 5 ]; then
        echo "c equals five"
fi

Logically, there's nothing wrong with the script. However, you see there's the possibility that the $c variable will not get set to 5 (or any other integer) and so in this case, if you run the script, it will fail with an error (unless you set NAME="fred" in the beginning).

To prevent the error, make sure $c will ALWAYS contain some integer, including zero, before comparing it. Tthere should either be an ELSE case to go with the IF test of the name, which sets c to some value other than 5; or, you should initialise c=0 at beginning of the script. So:

Code:

#!/bin/bash

NAME="bob"

if [ "$NAME" = "fred" ]; then
        c=5
else
        c=1
fi

if [ $c -eq 5 ]; then
        echo "c equals five"
fi

Above, I added an ELSE, which sets $c to an integer; Now, $c ends up being an integer, regardless of what the $NAME was. No error is possible now, and we do not need to initialize c=0 in the start of the script.

burgsprinta · 11-30-2010, 01:37 AM

Okay Thanks for all your help. After reading your replies I started over from scratch, and it works well now with no errors. Also, I added a countdown timer as well. Here is my new code. Try it out, and tell me what you think.

Code:

#!/bin/bash

#Script to set an alarm Clock, and use mplayer to wake up

#set alarm command

echo -e "Alarm Clock [a] or timer [t] (Case sensitive)?:"
read -N1 Choice

#if user Chose Alarm Clock
if [ $Choice == "a" ]; then
echo -e "\n"
setH=99
setM=99
currentH=99
currentM=99
hLeft=99
mLeft=99
echo -e "What Hour (24 Hour Format) Would you like to wake up?\n"
read setH
echo -e "What Minute?:  "
read setM

#get current time
currentH=`date +%H`
currentM=`date +%M`


echo -e "\nYou Selected $setH:$setM.\n"

echo -e "It is currently $currentH:$currentM.\n"



#correct for entries such as 1:01 01:03, anything where first digit
#is a 0.  There is probably an easier way, but I don't know it ;-)

#for setH
#--------------------------------------
if [ $setH == 00 ]; then
	setH=0
fi
if [ $setH == 01 ]; then
	setH=1
fi
if [ $setH == 02 ]; then
	setH=2
fi
if [ $setH == 03 ]; then
	setH=3
fi
if [ $setH == 04 ]; then
	setH=4
fi
if [ $setH == 05 ]; then
	setH=5
fi
if [ $setH == 06 ]; then
	setH=6
fi
if [ $setH == 07 ]; then
	setH=7
fi
if [ $setH == 08 ]; then
	setH=8
fi
if [ $setH == 09 ]; then
	setH=9
fi
#-----------------------------------------------

#for setM
#--------------------------------------
if [ $setM == 00 ]; then
	setM=60
	setH=$(($setH - 1))
fi
if [ $setM == 0 ]; then
	setM=60
	setH=$(($setH - 1))
fi
if [ $setM == 01 ]; then 
	setM=1
fi
if [ $setM == 02 ]; then
	setM=2
fi
if [ $setM == 03 ]; then
	setM=3
fi
if [ $setM == 04 ]; then
	setM=4
fi
if [ $setM == 05 ]; then
	setM=5
fi
if [ $setM == 06 ]; then
	setM=6
fi
if [ $setM == 07 ]; then
	setM=7
fi
if [ $setM == 08 ]; then
	setM=8
fi
if [ $setM == 09 ]; then
	setM=9
fi
#-----------------------------------------------

#for CurrentH
#--------------------------------------
if [ $currentH == 00 ]; then
	currentH=0
fi
if [ $currentH == 01 ]; then
	currentH=1
fi
if [ $currentH == 02 ]; then
	currentH=2
fi
if [ $currentH == 03 ]; then
	currentH=3
fi
if [ $currentH == 04 ]; then
	currentH=4
fi
if [ $currentH == 05 ]; then
	currentH=5
fi
if [ $currentH == 06 ]; then
	currentH=6
fi
if [ $currentH == 07 ]; then
	currentH=7
fi
if [ $currentH == 08 ]; then
	currentH=8
fi
if [ $currentH == 09 ]; then
	currentH=9
fi
#-----------------------------------------------

#for currentM
#--------------------------------------
if [ $currentM == 00 ]; then
	currentM=0
fi
if [ $currentM == 01 ]; then
	currentM=1
fi
if [ $currentM == 02 ]; then
	currentM=2
fi
if [ $currentM == 03 ]; then
	currentM=3
fi
if [ $currentM == 04 ]; then
	currentM=4
fi
if [ $currentM == 05 ]; then
	currentM=5
fi
if [ $currentM == 06 ]; then
	currentM=6
fi
if [ $currentM == 07 ]; then
	currentM=7
fi
if [ $currentM == 08 ]; then
	currentM=8
fi
if [ $currentM == 09 ]; then
	currentM=9
fi
#-----------------------------------------------
#I realize that was pretty redundant.  Does anyone Know a better way?

#correct for a period of 24 hours
if [ $setH == $currentH ]; then
	if [ $setM -le $currentM ]; then
		setH=$(( $setH + 24))
		echo -e "Quite a long Nap You're Taking... About 1 Day\n"
	fi
fi

#If the Current Hour is less than the set hour
#subtract for hours remaining

if [ $currentH -lt $setH ]; then
	hLeft=$(($setH - $currentH))


#if current Hour is greater than set Hour
else if [ $setH -lt $currentH ]; then
	hLeftA=$(($currentH - $setH))
	hLeft=$((24 - $hLeftA))
	
#if equal
else
	hLeft=0
	echo -e "\nShort nap.  $hLeft hours"
fi
fi

#Make script output hours set; use correct plurality of "hour" or "hours"
if [ $hLeft == 1 ]; then
	echo "You have $hLeft hour"
	else if [ $hLeft -gt 1 ]; then
		echo "You have $hLeft hours"
	fi
fi
#Do the Same as Above, but for the Minutes
#subtract for minutes remaining

if [ $currentM -lt $setM ]; then
	mLeft=$(($setM - $currentM))


#if current Hour is greater than set Hour
else if [ $setM -lt $currentM ]; then
	mLeft=$(($currentM - $setM))

#if equal
else
	mLeft=0
	echo " and no minutes"
fi
fi
#make script output minutes set, with correct plurality of "minute or "minutes"
if [ $mLeft == 1 ]; then
	echo " and $mLeft Minute\n"
	else if [ $mLeft -gt 1 ]; then
		echo " and $mLeft Minutes"
	fi
fi
# Subtract 1 Hour if more than 0 minutes (since part of the hour is taken by the minutes)
if [ $mLeft -gt 0 ]; then
	hleft=$(($hleft -1))
fi
#invoke sleep
if [ $mLeft -gt 0 ]; then
echo -e "\nSleeping for: $hLeft hours and $mLeft minutes"
fi

if [ $mLeft == 0 ]; then
echo -e "\nSleeping for: $hLeft hours."
fi

sleep $hLeft\h
echo -e "\nNow 0 hours and $mLeft minutes\n"
sleep $mLeft\m
echo -e "DONE\n"

#run alarm Command
mplayer ~/alarm.mp3
exit 0
fi


#if user chose Timer
if [ $Choice == "t" ]; then
echo -e "\n"
H=99
M=99
echo -e "How many Hours:  "
read H

echo -e "\nHow many Minutes: "
read M
echo -e "You Chose $H hours and $M minutes."

echo -e "Setting Timer For $H:$M"
sleep $H\h
sleep $M\m
echo -e "\nDONE\n"

#run alarm command
mplayer ~/alarm.mp3
exit 0
fi