Shell Programming and Scripting

The shell error message "Badly placed ()'s" can occur for a surprisingly simple oversight. If the script begins with a shell-invocation comment, but is missing the exclamation-point, it is simply a comment and not an invocation. If you attempt to execute it from a shell other than the shell you intended to invoke, you could get this error. For example, if you're using "tcsh" and try to execute a script with "#/bin/bash", it could fail for Badly placed ()'s. Doing something like "bash -n script_name" will NOT show errors because you're using bash to scan the script. And "bash -x script_name" will probably execute properly as well.

You need that "!" in the invocation line: #!/bin/bash

I find a vi search for [('"] allows me to verify the closing parens with % and count the quotes in and out. Figureing if the ) is in a different quoting space can be a problem. Good structural indentation helps identify quoted areas. Note that case statements can have wild card starting with ( so they do not confuse %, although case traditionally did not use them. If you have isolated () in character or string contexts, you can temporarily replace them with substitute strings like '~oparens' and '~cparens'. (The ~ is the rarest ascii visible glyph.)

You cannot blame tcsh or bash for the fact that exec() obeys the magic line. It is nice that you can ensure your scripts use the designed interpreter. If you source a file or feed the file to stdin, the magic is ignored (no exec()). You are even allowed one argument on the magic line, so you can say things like "#!/bin/awk -f" or "#!/bin/sed -f" and make scripts for tools not normally considered script interpreters. It saves a fork() and exec() over a shell script calling awk or sed.

Sir, I think you missed my point. All my () characters where matched. "bash -n script" did NOT show any syntax errors. My script had functions and I was running under a shell that did not recognize the bash-syntax of a function. Since my initial statement was #/bin/bash, which did NOT initiate bash, my current shell parsed the script and didn't understand the syntax. My point is simply this: If you write a script and see "Badly placed ()'s", be sure your shell-initialization statement is properly formatted: #!/bin/shell_name because it took me a long time and much wasted time looking for paren-mismatch problem when, in fact, the error was only related to shell-syntax differences between my current shell and the shell which was supposed to run the script.

Well, always be sure your magic is right, or bad things will happen. If you read the exec() man page carefully, you see that magic typos go to sh stdin not bash.

I wish I had a tool that would find errors in balance with all the potential quoting and bracketing characters: {}[]()<>'"` so ({)} would be flagged. Of course, it should know when these characters are dominating each other in the local context, e.g., '('.

Point taken. Thank you for your helpful post.