Re: tail weirdness

[Eric Blake]

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According to Igor Rivin on 2/6/2007 6:32 AM:
> On my Fedora core 6 system, this fails:
> 
> address@hidden tmp]$ tail +2 dog
> tail: cannot open `+2' for reading: No such file or directory

This is becoming a FAQ; would anyone care to add it to
http://www.gnu.org/software/coreutils/faq/coreutils-faq.html?

> address@hidden tmp]$ tail --version
> tail (GNU coreutils) 5.97

Consider upgrading - the lateset stable version is 6.7.  It will not
change the behavior of tail in your case, but has other improvements.

The short answer is that POSIX is the driving factor here, and that Fedora
core 6 has chosen POSIX 1003.1-2001 as their default.  Depending on which
version of POSIX you are compliant with, tail is specified to treat +3
differently.  This is documented in the NEWS for 5.90:

  A few usages still have behavior that depends on which POSIX standard is
  being conformed to, and portable applications should beware these
  problematic usages.  These include:

    Problematic       Standard-conforming replacement, depending on
       usage            whether you prefer the behavior of:
                      POSIX 1003.2-1992    POSIX 1003.1-2001
    sort +4           sort -k 5            sort ./+4
    tail +4           tail -n +4           tail ./+4
    tail - f          tail f               [see (*) below]
    tail -c 4         tail -c 10 ./4       tail -c4

Also, see 'info coreutils standards' - your choice of _POSIX2_VERSION in
the environment chooses which version of POSIX you want tail to comply to.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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