gzip tries to unpack/pack 1st the filename of $GZIP

[Devin Teske]

On Thu, 2010-10-14 at 16:48 +0200, Matthias Apitz wrote:
> El día Thursday, October 14, 2010 a las 10:39:13AM -0400, Lowell Gilbert escribió:
> 
> > Matthias Apitz <guru at unixarea.de> writes:
> > 
> > > Hello,
> > >
> > > I was facing a problem in some Makefile/shell-scripting and finally I
> > > could nail it down:
> > >
> > > when you set the environment variable GZIP to something, for example to
> > > let it point to gzip itself, it tries 1st to unpack this file:
> > >
> 	...
> 
> This was my fault. I overlooked it in the man page. SOrry;
> 
> > You need to fix the syntax on your 'export' lines.
> > Adding a semicolon before the "export" keyword (or
> > moving it to the next line) is the smallest change 
> > to do this.
> 
> Why?
> 
> $ FIX=foo export FIX
> $ env | fgrep FIX
> FIX=foo
> 
> 	matthias
> 

I'm with matthias on this one...

Here's the technical explanation:

When performing assignment in bourne/again shell, if the right-hand side
of the assignment (=) does not begin with either a single-quote or
double-quote, spaces will terminate the assignment and begin a new
command.

For example:

abc=123 echo hello, world
       ^
       |
end of assignment (start of new command; imagine implied semi-colon)

This produces two distinct commands:

1. abc=123
2. echo hello world


Contrast that with either:

abc="123 echo hello world"

or

abc=123\ echo\ hello,\ world

Both of which succeed in assigning `123 echo hello, world' to variable
`abc'.


Pop Quiz: What does the following do:

abc=123\ xyz echo hello

Answer:

1. assigns `123 xyz' to variable `abc'
2. executes: echo hello

Second Pop Quiz:

abc="123 xyz" echo hello

Answer:

1. assigns `123 xyz' to variable `abc'
2. executes: echo hello


This obviously doesn't work in tennex/c shell:

# echo $0 $SHELL
-csh /bin/csh
# abc=123
abc=123: Command not found.
# ls -li `which csh tcsh`
1411 -r-xr-xr-x  2 root  wheel  651964 Jan 23  2007 /bin/csh
1411 -r-xr-xr-x  2 root  wheel  651964 Jan 23  2007 /bin/tcsh

-- 
Cheers,
Devin Teske

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