random-gradient | Generate beautiful random gradients | Runtime Evironment library

This error will happen if the shell running this code is not actually bash. It's noteworthy that your script doesn't include a shebang -- without #!/usr/bin/env bash or another shebang, the interpreter used is unspecified. (Explicitly specifying sh yourscript will override the shebang and force sh, just as bash yourscript will ignore the shebang and use bash, but that's neither here nor there).

function is not a keyword in standard POSIX sh -- it's a ksh extension which bash adopted. Consequently, to a POSIX shell, the { in function freespace { is not syntax -- it's an argument to be passed to a command named function.

By contrast, the } is parsed as syntax, but it doesn't match with any syntactic opening brace; hence, your error.

In standards-compliant syntax, the declaration would be: