Good question. Actually, there are a couple of special characters
intercepted by the shell, bash . The character
``*'', an asterix, says ``replace this word with all the files
that will fit this specification''. So, the command cp data*
~/backup, like the one above, gets changed to cp
data-new data1 data2 data5
~/backup before it gets run.
To illustrate this, let me introduce a new command, echo . echo is an extremely simple command; it echoes back, or prints out, any parameters. Thus:
As you can see, the shell expands the wildcard and passes all of the files to the program you tell it to run. This raises an interesting question: what happens if there are no files that meet the wildcard specification? Try echo /rc/fr*og and see what happens...bash will pass the wildcard specification verbatim to the program.
One word about that, though. Other shells, like tcsh , will, instead of just passing the wildcard verbatim, will reply No match.
The last question you might want to know is what if I wanted to have data* echoed back at me, instead of the list of file names? Well, under both bash and tcsh, just include the string in quotes: