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diff --git a/dos/README.txt b/dos/README.txt new file mode 100644 index 0000000..0e8f6c0 --- /dev/null +++ b/dos/README.txt @@ -0,0 +1,123 @@ + +XZ Utils on DOS +=============== + +DOS-specific filename handling + + xz detects at runtime if long filename (LFN) support is + available and will use it by default. It can be disabled by + setting an environment variable: + + set lfn=n + + When xz is in LFN mode, it behaves pretty much the same as it + does on other operating systems. Examples: + + xz foo.tar -> foo.tar.xz + xz -d foo.tar.xz -> foo.tar + + xz -F lzma foo.tar -> foo.tar.lzma + xz -d foo.tar.lzma -> foo.tar + + When LFN support isn't available or it is disabled with LFN=n + environment setting, xz works in short filename (SFN) mode. This + affects filename suffix handling when compressing. + + When compressing to the .xz format in SFN mode: + + - Files without an extension get .xz just like on LFN systems. + + - *.tar files become *.txz (shorthand for *.tar.xz). *.txz + is recognized by xz on all supported operating systems. + (Try to avoid confusing this with gzipped .txt files.) + + - Files with 1-3 character extension have their extension modified + so that the last character is a dash ("-"). If the extension + is already three characters, the last character is lost. The + resulting *.?- or *.??- filename is recognized in LFN mode, but + it isn't recognized by xz on other operating systems. + + Examples: + + xz foo -> foo.xz | xz -d foo.xz -> foo + xz foo.tar -> foo.txz | xz -d foo.txz -> foo.tar + xz foo.c -> foo.c- | xz -d foo.c- -> foo.c + xz read.me -> read.me- | xz -d read.me- -> read.me + xz foo.txt -> foo.tx- | xz -d foo.tx- -> foo.tx ! + + Note that in the last example above, the third character of the + filename extension is lost. + + When compressing to the legacy .lzma format in SFN mode: + + - *.tar files become *.tlz (shorthand for *.tar.lzma). *.tlz + is recognized by xz on all supported operating systems. + + - Other files become *.lzm. The original filename extension + is lost. *.lzm is recognized also in LFN mode, but it is not + recognized by xz on other operating systems. + + Examples: + + xz -F lzma foo -> foo.lzm | xz -d foo.lzm -> foo + xz -F lzma foo.tar -> foo.tlz | xz -d foo.tlz -> foo.tar + xz -F lzma foo.c -> foo.lzm | xz -d foo.lzm -> foo ! + xz -F lzma read.me -> read.lzm | xz -d read.lzm -> read ! + xz -F lzma foo.txt -> foo.lzm | xz -d foo.lzm -> foo ! + + When compressing with a custom suffix (-S .SUF, --suffix=.SUF) to + any file format: + + - If the suffix begins with a dot, the filename extension is + replaced with the new suffix. The original extension is lost. + + - If the suffix doesn't begin with a dot and the filename has no + extension and the filename given on the command line doesn't + have a dot at the end, the custom suffix is appended just like + on LFN systems. + + - If the suffix doesn't begin with a dot and the filename has + an extension (or an extension-less filename is given with a dot + at the end), the last 1-3 characters of the filename extension + may get overwritten to fit the given custom suffix. + + Examples: + + xz -S x foo -> foox | xz -dS x foox -> foo + xz -S x foo. -> foo.x | xz -dS x foo.x -> foo + xz -S .x foo -> foo.x | xz -dS .x foo.x -> foo + xz -S .x foo. -> foo.x | xz -dS .x foo.x -> foo + xz -S x.y foo -> foox.y | xz -dS x.y foox.y -> foo + xz -S .a foo.c -> foo.a | xz -dS .a foo.a -> foo ! + xz -S a foo.c -> foo.ca | xz -dS a foo.ca -> foo.c + xz -S ab foo.c -> foo.cab | xz -dS ab foo.cab -> foo.c + xz -S ab read.me -> read.mab | xz -dS ab read.mab -> read.m ! + xz -S ab foo.txt -> foo.tab | xz -dS ab foo.tab -> foo.t ! + xz -S abc foo.txt -> foo.abc | xz -dS abc foo.abc -> foo ! + + When decompressing, the suffix handling in SFN mode is the same as + in LFN mode. The DOS-specific filenames *.lzm, *.?-, and *.??- are + recognized also in LFN mode. + + xz handles certain uncommon situations safely: + + - If the generated output filename refers to the same file as + the input file, xz detects this and refuses to compress or + decompress the input file even if --force is used. This can + happen when giving an overlong filename in SFN mode. E.g. + "xz -S x foo.texinfo" would try to write to foo.tex which on + SFN system is the same file as foo.texinfo. + + - If the generated output filename is a special file like "con" + or "prn", xz detects this and refuses to compress or decompress + the input file even if --force is used. + + +Bugs + + xz doesn't necessarily work in Dosbox. It should work in DOSEMU. + + Pressing Ctrl-c or Ctrl-Break won't remove the incomplete target file + when running under Windows XP Command Prompt (something goes wrong + with SIGINT handling). It works correctly under Windows 95/98/98SE/ME. + |