shell script command not found when comparing stri

问题:

I have this script

#!/bin/sh        
if [ $# -ne 3 ] ; then
            echo "param 1, param2, and A or B "
            exit 1;

    elif [ $# -eq 3 ]; then
                    if [$3 = "A"] ; then
                                    echo "A"
                    elif [$3 = "B"]; then
                                    echo "B"
                    fi

fi

It is basically checking if param 3 is A or B, and do echo. But it returns:

./test.sh: line 6: [A: command not found
./test.sh: line 8: [A: command not found

I tried to use -eq for comparison, but it still does not work. How can I fix this problem?

回答1:

I'm sure this has come up before, but -- [ is actually a command. You need a space after the [ in order for the shell to find it.