On Friday 09 March 2007 01:13, Les wrote:
> I have a question about du though. On the other machine where I
wanted to
> find out the size of my soundfiles directory, du couldn't access it
> because it was named "Sounds Library" , without the quotes. I renamed it
> putting a hyphen between the 2 words, and then du accessed the directory
> ok, but all of the subdirectories are multi worded without any hyphens,
> and du didn't have any problem with them. Any reason why du will not
> access the main directory without hyphenated words, and yet has no
> problem with all the subdirectories?
>
> It's not a big deal, just puzzling.
>
> btw. The now Sounds-Library (with the hyphen) is on a separate harddrive
> so I have to run du as.
>
> du -sh /mnt/hdb5/Sounds-Library
Hi, Nigel,
The reason a command won't parse correctly with a space in the file
name is due to the tokenizer used by the shell. It cannot deal with
spaces in filenames. A space is the end of the word to the tokenizer
unless it is inside Quotes or escaped in some way. Thus the command du
xxx yyy is going to look for files xxx and then yyyy. This is true of
most systems. otherwise there would be no way to chose which way to
parse a command with several arguments, for example:
cat xxx yyy aaa bbb ccc ddd > temp.txt
In this case should the result consist of files xxx, yyy, zzz, bbb,
ccc, and ddd all being concatenated to a file called temp.txt, or should
it be xxx yyy, zzz bbb, and ccc ddd? Moreover how would an unambiguous
error message tell the operator what was wrong? What if files xxx, yyy
zzz, bbb zzz, and ddd were all present? Is this what the operator
meant?
This is why a good administrator doesn't put spaces in system control
files. It leads to ambigousity when working on the system, leading to
errors and system corruption. Typo's that would be caught might not be
if spaces are allowed into filenames.
On the other hand, once a directory is opened, the file names are read
via a special command designed for the OS, and if the OS permits spaces,
the entire file name up to the end charactor (generally control-Z or
NULL). Thus the sub directories and files will be correctly handled.
But with spaces in the names, error messages regarding parsing, or
tracing the file contents may be ambiguous to the operator. It is not
illegal to put spaces in filenames, but is should be considered a bad
practice, and avoided. But it is your system, so YMMV.
Regards,
Les H
Thanks Les for that very thorough explanation. I will be more carefull about
spaces in the future.
A related question, is. How do I find out how many files are in the
Sounds-Library directory, including all subdirectories. I looked at ls, but
that will only give a list of files, as far as I can see.
Thanks.
Nigel.