Re: bash syntax question

[Alfredo Finelli <0x4146@gmail.com>]

On Friday 06 June 2008 12:59, Malte Forkel wrote:
> I recently came across the following example for switching time
> zones:
>
> $ date
> Fr 6. Jun 12:49:30 CEST 2008
> $ TZ=UTC date
> Fr 6. Jun 10:49:35 UTC 2008
>
> Could someone please explain to me the general shell syntax involved
> here? I did not know that I could put an assignment and a command on
> one line. My dull approach would have been [...]

The 'date' command runs in a child process for which the bash shell has 
to determine the environment.  Parameter assignments are inherited in 
that environment (i.e. the 'date' command sees them) in two cases:  
either when the variable is not only declared but also exported or when 
the assignment is provided on the command line right before the command 
itself.  From the man page:

  The environment for any simple command or function  may
  be  augmented temporarily  by  prefixing  it with parameter
  assignments, as described above in PARAMETERS.  These assignment
  statements affect only the environment seen by that command.

For more information you may want to read the "Command execution 
environment" section in the Bash man page.

Best regards.

Alfredo