'unexpected token' in PowerShell when fully pathing executable

Just trying to better understand why the second item below does not work. The first item is simple, the second seems clearer, the third seems unintuitive.

# My path includes pscp so this works.
pscp.exe -i $PRIVATE_KEY $file ${PROXY_USER}@${PROXY_HOST}:${PROXY_DIR}

# This does not work. I get unexpected token error. Why? What does that mean?
$PUTTY_PATH\pscp.exe -i $PRIVATE_KEY $file ${PROXY_USER}@${PROXY_HOST}:${PROXY_DIR}

# & is required to solve the problem.
& "$PUTTY_PATH\pscp.exe" -i $PRIVATE_KEY $file ${PROXY_USER}@${PROXY_HOST}:${PROXY开发者_JAVA技巧_DIR}

That's because this is also considered a parse error:

"foo"\pscp.exe 

Whereas this parses correctly as you have found:

"$PUTTY_PATH\pscp.exe"

That resolves to a valid string but as you have already noticed, a string doesn't execute. You have to use the call operator & to invoke the command that is named by the string that follows.

It's taking the \ to be part of the variable name, and complains because it is not legal. If you are using this snippet like i would, by putting it into a .ps1 file in your path, then i would just cd over to $putty_path if you don't want to have pscp.exe in your global PATH env var.

Just guessing, but I have a feeling you might be misusing the curly braces. Are you trying to get the environment variable PROXY_USER instead? Typically the curly brackets are used for starting a new statement block.

$Env:PROXY_USER

Also, you may want to encapsulate that proxy info inside a string to ensure it is treated as a single argument:

"$Env:PROXY_USER@$Env:PROXY_HOST:$Env:PROXY_DIR"