On Tue, Feb 26, 2008 at 05:13:12PM -0600, Les Mikesell alleged:
Garrick Staples wrote:
On Tue, Feb 26, 2008 at 04:33:30PM -0600, Les Mikesell alleged:
Does anyone have a quick reference to the order of operations as the shell parses a command line (variable parsing,i/o redirection, wildcard and variable expansion, splitting on IFS, quote removal, command substitution etc.)? That's really the first thing you need to know about the shell and if there is a simple description it must be buried in the middle of some obscure manual.
This is from the "EXPANSION" section of the bash manpage:
The order of expansions is: brace expansion, tilde expansion, parameter, variable and arithmetic expansion and command substitution (done in a left-to-right fashion), word splitting, and pathname expansion.That's one step in the bigger picture. I want the one that includes variable assignment, i/o redirection, quote removal, and a few other operations. I think I knew that a few decades ago, but now I don't even know where to look it up.
That's pretty much the entire process for your basic expression. Quotes are obeyed the entire time, but are actually _removed_ after the expansion. And finally, file descriptors are opened the command is executed.
I don't think you can write a simple list because the actual process is too complex. It would really be a tree or flowchart.