Bash code: while loop does not work

Question

I tried to write a little bash code to write a temperaturelog. The into the logging file 100 timepoints and measuring points are written, then the data is moved to a temporary file and it should begin to record again into the original file. The temporary file is removed every 100 seconds because I only need the last minutes of record and want to prevent garbage.

Besides that the code might look unnecessarily complicated (I am a beginner) - Where is the mistake? I expected the counter (printed just to see what is going on) would count to 100 but it only prints out:

1
2

and it writes only two timepoints instead of 100 into the files. Here is the code:

#!/bin/bash

COUNTER=0
#Initial temporary file is created
echo '' > temperaturelogtemporary.txt;

#100 timepoints are written into temperaturelog.txt   
while true; do
    echo `date` '->' `acpi -t`>> temperaturelog.txt;
    sleep 1;
    #as soon as 100 timepoints are recorded...      
    if [[ $COUNTER > 100 ]];
        then
                    #...the old temporary file is removed and 
                    #the last records are renamed into a new temporary file 
            rm temperaturelogtemporary.txt;
            mv temperaturelog.txt temperaturelogtemporary.txt;
            COUNTER=0;
    fi
    COUNTER=$(($COUNTER + 1));
    echo $COUNTER;

done

user2719058 · Accepted Answer · 2013-11-07 13:18:12Z

2

Referring to the accepted answer: while

[[ $COUNTER -ge 100 ]]

works, I still would recommend to use the equivalent

((COUNTER >= 100))

instead, because it is more readable.

answered Nov 7, 2013 at 13:18

user2719058

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2 Comments

aldorado Over a year ago

when exactly does one use the semicolons? They are still needed right?

user2719058 Over a year ago

You need them only if you put multiple statements on one line. In your script, you can strip most of them.

Vladimir Vodolazkiy · Accepted Answer · 2013-11-07 11:04:25Z

1

Just change ">" sign for "-ge".

if [[ $COUNTER -ge 100 ]];

Bash language is very very old - string and numeric comparisons performed with different keywords.

answered Nov 7, 2013 at 11:04

Vladimir Vodolazkiy

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1 Comment

user2719058 Over a year ago

Note that -ge is >=, not >.

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