具有IF语句的Bash脚本，执行“ gem”并检查结果

Question

I am trying to write a bash script that checks if a gem is installed. If the gem is installed I will do option A. If not, I will do option B.

To see if the gem is installed I use:

gem list -i "^gemname$"

This prints "true" or "false" to the screen. I think it outputs the text "true" and "false" but I am not sure if itself has a return value.

The gem i am searching for is "xcpretty" and my script is:

if [[$(gem list -i "^xcpretty$") == true]]; then
    echo "Found XCPRETTY do other things"
else
    echo "Cant find XCPRetty do things"
fi

This fails with the error: .xxxxx: line 1: [[false: command not found

Because the gem is not installed on my system, it returned "false". But how do I compare what it returned with "false"?

Thanks!

Answer 1

在[[和之前]]之后添加空格。

[[ $(gem list -i "^xcpretty$") == true ]]