How to write shell script?

Question

I want to write a shell that runs until something is written to a file (by another process). I have written this:

PID_FILE=log.txt
DONE=0
while [$DONE -eq 0]
do 
    cat $PID_FILE | while read LINE 
    do
    if [$LINE -neq ""]; then    
        echo "Do stuff here"
        $DONE=1
    fi  
    done
done    
echo "DONE"
echo "">$PID_FILE

but I get

test.sh: 3: test.sh: [0: not found
DONE

[$DONE -eq 0] => [ $DONE -eq 0 ], btw you can use the test program in place of the [ command. — BigMike
– BigMike, Commented Feb 28, 2013 at 8:38

Community · Accepted Answer · 2017-05-23 12:27:14Z

6

This line:

while [$DONE -eq 0]

Needs spaces around the square brackets:

while [ $DONE -eq 0 ]

As does this one:

if [$LINE -neq ""]; then

Like this:

if [ $LINE -neq "" ]; then

It helps when you know that \[ is a command. See Why should be there a space after '[' and before ']' in the Bash Script for an explanation.

edited May 23, 2017 at 12:27

CommunityBot

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answered Feb 28, 2013 at 8:38

johnsyweb

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