# Bash: optionally passing arguments to a command

bashbash-scriptingcommand-line-argumentsshell-script

I'm trying to add arguments to a command call depend on another variable. Please look at the shell scripting code:

curl \
$([ -z "${title}" ] || echo --data-urlencode title=${title}) \ http://example.com  In the example, if title is given not null, an argument will be added to curl. This does not work correctly if title contains spaces. Also I couldn't surround $(...) with quotations, because if title is null, it will yield an unexpected empty argument to curl.

What should I do to make it work as expect.

I've solved the problem with the bash ${var:+...} syntax, (reference). The script now changes to curl \${title:+ --data-urlencode "title=\${title}"} \
http://example.com


which works perfectly.

Also see: