[R] png overwrites upper/lower case filenames

[Timo Becker]

Dear R users,

when I create files with the png graphics device, it overwrites existing 
files which differ concerning upper/lower case file names.
For example, I want to create four files named "a.png", "A.png", "b.png" 
and "B.png" which contain the corresponding letters:

png("a.png")
plot(1, type="n")
text(1, label="a")
dev.off()

png("A.png")
plot(1, type="n")
text(1, label="A")
dev.off()

png("B.png")
plot(1, type="n")
text(1, label="B")
dev.off()

png("b.png")
plot(1, type="n")
text(1, label="b")
dev.off()

These commands create a file named "a.png" which contains the letter "A" 
and a file named "B.png" which contains the letter "b".
The old file name is retained, but overwritten with the output of the 
new png device with the same case-insensitive file name.
I'm sure I missed something. Can anyone tell me how to create files 
whith case-sensitive names with the same letters?

R version 2.2.1, 2005-12-20, i386-pc-mingw32

Regards,
Timo

-- 
Timo Becker
Phonetics
Austrian Academy of Sciences
Acoustics Research Institute