On Fri, Sep 16, 2022 at 1:20 PM Rob Landley <[email protected]> wrote:
> On 9/15/22 16:32, enh wrote: > > On Thu, Sep 15, 2022 at 1:45 PM Rob Landley <[email protected] > > <mailto:[email protected]>> wrote: > > > > On 9/15/22 07:30, Yi-yo Chiang via Toybox wrote: > > > grep is slow when the number of patterns is large. > > ... > > > xxd -p -c 0 -l 40 /dev/urandom > > > > Huh, WHY does that produce two lines of output? > > > > $ xxd -p -c 0 -l 40 /dev/urandom > > 1fcf13e1b4844ba209fb9958bde26a13577c577744f1b1290240d03f4f8e > > 644fd0687c39b1aa8a68 > > > > Behavior is consistent between toybox xxd and debian's, but Elliott > sent in the > > xxd implementation and I don't use it much, so... Feeding in -c 40 > and -c 80 > > make no difference? > > > > i think that's actually a bug caused by this: > > > > // Plain style is 30 bytes/line, no grouping. > > > > if (FLAG(p)) TT.c = TT.g = 30; > > > > should presumably be > > > > // Plain style is 30 bytes/line, no grouping. > > if (FLAG(p)) { > > if (!TT.c) TT.c = 30; > > if (!TT.g) TT.g = 30; > > } > > > > ? > > Except we didn't set -g so it would still be set to 30, which is going to > stick > spaces into the output. > > And xxd_main() starts with if (!TT.c) TT.c = blah so it would never be > zero at > that point unless we reorder the code, and then once THAT'S fixed -c 0 is > still > !TT.c and if I switch that to if (FLAG(c)) to allow c = 0 through (which > the > range in the optstr is allowing) it's used to cap the length in readall() > meaning the first read becomes EOF so no output gets produced. > > > certainly "real" xxd works for me on macos and debian, both of which > have the > > same version of xxd: > > > > ~$ xxd --version > > xxd 2022-01-14 by Juergen Weigert et al. > > ~$ xxd -p -c 0 -l 40 /dev/urandom > > > ac160632955aa9d938e60d3533cbcf0febb4decdd12f130e415913ff1fe6e2abcaf7c4a8e980de7a > > See, this is extra weird: nothing set -g so it should default to 2. > Somehow it > knows to set itself to... I'm guessing 0. Did -p -c 0 get special cased, > or did > -p change its default to avoid any breaks even without the -c 0? (Sounds > like > the latter is more likely, but I tried "yum install xxd" on my fedora 36 > VM and > yum doesn't know what an xxd is. > > (Tangent. Seems like xxd behavior is different everywhere, I should be careful and also note my expected output next time I use xxd as a random string generator.) On my debian machine (with the same 2022-01-14 build as Elliott), `man xxd` says... * -p: Plain text output, '-g' is ignored, '-c' defaults to 30, '-c 0' results in one long line (yes '-p -c 0' is a special case for "plain text no wraping no grouping") * doesn't say what would happen with '-c 0' otherwise > > ah, but on another box with 2021-10-22 it's broken. so it looks like > "real" xxd > > had the same bug and fixed it recently? > > Eh, seems more like a design decision than a bug. Before -p was > wordwrapping the > hexdump output and now it isn't. I dunno if it always isn't, or just with > -c 0? > We didn't set -g and it has a nonzero default value (1, 2, or 4 depending > on > barometric pressure)... > > I also note that the man page says -g 0 switches off grouping, but does > NOT say > that -c 0 switches off columns? In the V1.10 version I have installed, -c 0 > seems to be a NOP: > > $ sha1sum < /dev/null | xxd -c 0 > 00000000: 6461 3339 6133 6565 3565 3662 3462 3064 da39a3ee5e6b4b0d > 00000010: 3332 3535 6266 6566 3935 3630 3138 3930 3255bfef95601890 > 00000020: 6166 6438 3037 3039 2020 2d0a afd80709 -. > > Once again: easy to change the behavior, hard to tell what the changed > behavior > should be. Easiest is to have -p force -g to 0 and -c to huge (stomping > whatever > else got set in both). I could also teach -c that 0 means infinite (well, > sizeof(toybuf) implementation limit which is still bigger than the 256 > directly > settable limit that I have no idea why it's there) if that's actually a > thing...? > > (Grumble grumble no standard and the reference implementation has version > skew...) > > Rob > -- Yi-yo Chiang Software Engineer [email protected] I support flexible work schedules, and I’m sending this email now because it is within the hours I’m working today. Please do not feel obliged to reply straight away - I understand that you will reply during the hours you work, which may not match mine.
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