I would like to check if a path is valid in Bash. However the lower code always returns false, even if the path is valid.

# Test if path is valid
mytest=$(test -e $myPath && test -f $myPath)

if [[ ! $mytest ]]; then 
        echo 'Path invalid. Stop..'
        exit 
fi

How can I improve the code?

CodePudding user response：

$() command substitution captures the output of a command, not the exit status.

• $mytest will be empty
• [[ ... ]] with only one operand (not counting !) returns "true" if the operand is not empty. Because $mytest is empty, the test result is "false negated"

To fix it:

1. following your style:

   test -e "$myPath" && test -f "$myPath"   # quote your variables
   mytest=$?                                # capture the exit status immediately
   
   if [[ $mytest -ne 0 ]]; then 
       echo 'Path invalid. Stop..'
       exit 
   fi
   

2. more idiomatic bash:

   if [[ ! (-e $myPath && -f $myPath) ]]; then 
       echo 'Path invalid. Stop..' >&2
       exit 
   fi