Hi there,

As you know, we can group a list of commands in either (list) form or { list;}. I know the difference between the two. (list) make the command list to be executed in a subshell while the commands gathered in { list;} are executed in the current shell. My question here is about the syntax. You see, for (list), it is not required to insert a space between ( and list. But it is required for { list;}. The man page for ksh says { is a keyword and that is why there must be a white space b/w { and list. Then ( is not a keyword? If no, what ( should be called? Also, the list in { list; } is required to end with ';'. What does it mean? Why the shell is designed this way? I know it is not easy to be clarified but hopefully here is someone insightful in these things

In ksh, '{' and '}' are reserved words not keywords. The space after the opened '{' in { list;} is simply a way of providing additional information to the ksh parser to allow it correctly parse the statement.

If you want a more detailed understanding, you will need to look at the ksh93 source code which is freely available at AT&T Software Download. The relevant files are ../cmd/ksh93/sh/expand.c and ../cmd/ksh93/sh/lex.c