Q: Can I do filename globbing with DJGPP?
Q: I call my program with an argument x*y and it complains
about something called xyzzy??....
Q: I cannot find a way to use the /? switch with my
programs!
A: The filename globbing in DJGPP is done by the start-up code,
before your main function is called. Unlike other DOS-based
compilers, where you must link your program with a special object module
if you want the program to get expanded filenames, in DJGPP this is
considered normal behavior and is performed by default on behalf of
every DJGPP program. The x*y above was expanded to a file called
xyzzy which was probably present in the current working
directory; and /? is by default expanded to the list of
one-letter files/directories you happen to have in the root directory of
the current drive. (If you don't want the default expansion, refer to
how to disable globbing.)
In DJGPP, filename globbing works like in Unix, which is more general than the usual wildcard expansion, both in DOS and even in Windows. The DJGPP wildcard expansion understands the following constructs with special meta-characters:
?
*
[aA_]
[a-d]
[!a-z]
...
.../*
Unlike DOS, the * and ? meta-characters can appear
anywhere in the filename pattern, like in [a-z]*[0-9].*pp.
You can also use * instead of directories, like in
*/*/*.c, but not on drive letters (e.g., [a-c]:/
won't work).
Note that *.* only picks up files that actually have an
extension. This is contrary to the usual DOS practice where it means
all the files, with or without extension. Use * to get
files with and without extensions.
An argument which cannot be expanded (no filenames matching that
particular pattern) will be passed to the program verbatim. This is
different from what you might see under Unix, where some shells (like
csh) would say something like "No match" and won't call your
program at all. DJGPP's behavior in this case is like shells of the
Bourne legacy (sh, ksh, and bash).
If the wildcards include upper-case or mixed upper- and lower-case
letters, the letter-case of the files is not ignored on Windows 9X when
expanding the wildcards. For example, [A-D]* will not
match a file called aFileName. Upper-case letters in wildcards
also disable automatic down-casing of short 8+3 file names returned by
the code that expand wildcards (even on plain DOS). By contrast, if the
wildcards include only lower-case letters, the letter-case is ignored
during expansion, and short 8+3 file names are automatically down-cased,
unless the environment variable FNCASE is set to y. The
effect of setting FNCASE is fully described in the DJGPP C
Library reference, under the _preserve_fncase function; type
info libc alphabetical _preserve_fncase from the DOS prompt.