this post was submitted on 15 May 2024
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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
/devbut stdin and then complain that it's a terminal and refuse.Quoth POSIX on the
fflag:That is GNU is compliant, here, the default is system-dependent.
f -is required to be stdin, though, so you canbunzip2 foo.tar.bz2 | tar xf -or such in a portable manner, don't have to rely on tar having azoption (which is nonstandard) or it auto-detecting compression (even more nonstandard). What is not standard either istar -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 asdd, you can interpret how tar does things in the same way asgit 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,
lsdoes, e.g.rmdoesn't on account of only taking file names as arguments.ddis 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.