Bash comparing stored "boolean" value with what?

Question

I'm trying to make a program that takes in one argument, a file, and then checks what has happened to the file 60 seconds later. To do this, I need to store the result from `-e $1` in a variable and then check it 60 seconds later. I can not seem to be able to make the `if` expression listen to me, and I know it's wrong. For testing purposes this script just prints out immediately the result of the comparison. Looking forward to a working sample of this, I don't know how many versions I've made of this tiny program. Thanks! It's due tomorrow, any help is very much appreciated! ``` #!/bin/bash onStartup=$(test -e $1) if [ -e "$1" ]; then unixtid1=$(date +"%s" -r "$1") #To check if the file was edited. echo $unixtid1 fi sleep 3 #Here trying to be able to compare the boolean value stored in the #start of the script. True/False or 1 or 0? Now, both is actually printed. if [[ $onStartup=1 ]]; then echo "Exists" fi if [[ $onStartup=0 ]]; then echo "Does not exists" fi ```

Accepted Answer

Use `$?` special shell variable to get the result of the command. Remember that return value of `0` means `true`. Here is modified script

```
#!/bin/bash
test -e $1
onStartup=$?

if [ $onStartup -eq 0 ]; then
unixtid1=$(date  +"%s" -r "$1") #To check if the file was edited. 
echo $unixtid1
fi
sleep 3

#Here trying to be able to compare the boolean value stored in the
#start of the script. True/False or 1 or 0?
if [[ $onStartup -eq 0 ]]; then
echo "Exists"
else
echo "Does not exists"
fi
```

Your original example tried to store a literal output of the `test` command in the onStartup variable. The literal output of the `test` command is an empty string, that's why you did not see any output.

Bash comparing stored "boolean" value with what?

Solution

Problem