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

[Giorgos Keramidas]

On Thu, 14 Oct 2010 10:36:59 +0200, Matthias Apitz <guru at unixarea.de> wrote:
> 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:
>
> $ GZIP=/usr/bin/gzip export GZIP
> $ $GZIP -dc source.tar.gz | wc -l
> gzip: /usr/bin/gzip: not in gzip format
>   645770
>
> o
>
> $ GZIP=bla export GZIP
> $ gzip -dc source.tar.gz | wc -l
> gzip: can't stat: bla: No such file or directory
>   645770
>
> Why is this? It's not mentioned in the man page.

Look at the info documentation of gzip:

.---[ info gzip 'Environment' ]-----------------------------------------
| 5 Environment
| *************
|
| The environment variable `GZIP' can hold a set of default options for
| `gzip'.  These options are interpreted first and can be overwritten by
| explicit command line parameters.  For example:
|
|      for sh:    GZIP="-8v --name"; export GZIP
|      for csh:   setenv GZIP "-8v --name"
|      for MSDOS: set GZIP=-8v --name
|
|    On VMS, the name of the environment variable is `GZIP_OPT', to avoid
| a conflict with the symbol set for invocation of the program.
|
`-----------------------------------------------------------------------