linuxmemes @lemmy.world LainTrain @lemmy.dbzer0.com 6 mo. ago

Old XKCD, still relevant

Was trying to extract a totally legit copy of Skate 3 I downloaded today to play on my Steam Deck

156

You're viewing a single thread.

156 comments

tar -xvf or we all kill
- shouldnt there be a filename argument ?
  
  Yes. However, if you had skipped the -f, it would have been valid. Without the filename argument, it assumes it should extract from the tape drive (TAR = Tape ARchive). The tape device is probably something like /dev/rmt0, but you don't need to specify that. Using the -f is technically an exception which means "instead of extracting from the tape like you'd normally do, pretend that this file is the tape device instead."
  
  GNU tar, at least a modern one, that is the one that happens to come with my system, won't try to read from /dev but stdin and then complain that it's a terminal and refuse.
  
  Quoth POSIX on the f flag:
  
  Use the first file operand [...] as the name of the archive instead of the system-dependent default.
  
  That is GNU is compliant, here, the default is system-dependent. f - is required to be stdin, though, so you can bunzip2 foo.tar.bz2 | tar xf - or such in a portable manner, don't have to rely on tar having a z option (which is nonstandard) or it auto-detecting compression (even more nonstandard). What is not standard either is tar -x: Tar doesn't take leading hyphens. Tar is one of those programs so old its command line syntax got standardised before command line syntax standards were established. OTOH it's not nearly as bad as dd, you can interpret how tar does things in the same way as git pull: It's a subcommand, not a flag.
  
  "one of those programs so old its...syntax got standardized before command line syntax standards were established." --This is wild to learn, but also confusing. How does tar not take leading hyphens, but I've only ever used it as such without error of any kind? Not even bragging I've been doing that for 10+ years too lol
  
  Hmm. Actually you prompted me to dig a bit deeper: tar goes all the back to Version 7 UNIX, 1979, but the command line syntax is shared with tap, included in Version 1, man page dated to 1971-11-03. Development of C started 1972. Might've been written in B, you'd have to unearth a source archive I bet it's around somewhere. But anyway if you look through the other Version 1 commands a lot of them don't take hyphen commands, ls does, e.g. rm doesn't on account of only taking file names as arguments.
  
  dd is actually younger, Version 5, 1974, the syntax apparantly comes from IBM's JCL.
  
  Admittedly, that's all before my time.
  
  Both BSD and GNU tar take hyphens, I don't really have any experience with anything else but a short stint with Solaris in the early 2000s (very emphatically before Sun got gobbled up by Oracle) and I don't remember hyphens tripping me up. Much unlike killall. And I'm apparently not alone in that.
  
  I definitely still killed us all, but at the same time how are you supposed to know any of the filenames if none are given from the comic? I guess my real answer is to 'tar -xvf' then hit tab with hopes of decent file completion functionality lol
  
  tar -czf $(ls | head -n1) if we dont trust globs
  
  or run find in /bin or something
- ya blew it kid

You've viewed 156 comments.