Re: head and tail

[Eric Blake]

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According to Chuck Simmons on 7/13/2007 9:31 PM:
> Since head and tail have similar functionality, they should respond to
> similar command line arguments in similar ways except that one command does
> the head of the file and one does the tail.

Sorry, but POSIX does not specify these two programs symmetrically.  POSIX
only specifies head to support positive numbers (so as a GNU extension, we
make the negative number count from the opposite direction).  On the other
hand, POSIX specifies tail's behavior for no sign, negative sign (both
from the end), and positive sign (from the beginning).

http://www.opengroup.org/onlinepubs/009695399/utilities/head.html
http://www.opengroup.org/onlinepubs/009695399/utilities/tail.html

So, what you want is:

first portion of file: head -n 1
last portion of file: tail -n 1
all but first portion of file: head -n -1
all but last portion of file: tail -n +1

Yes, it is unfortunate, but that is because POSIX merely standardized
existing practice, and 30 years of scripting would break if we were to
change it now.

> address@hidden:~$ tail --version
> tail (GNU coreutils) 5.93

This is an old version.  You may want to consider upgrading; the latest
stable version is 6.9.

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

Eric Blake             address@hidden
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