Re: /etc/shells management

[Nicolas François <nicolas.francois@centraliens.net>]

On Mon, Sep 08, 2003 at 03:48:37AM -0500, Branden Robinson wrote:
> I do continue to think that:
> 
> if [ -n "$var" ]
> 
> is more readable than
> 
> if [ "${var+set}" = "set" ]

both are not equivalent:
  the first one test if var is empty or unset
  the second one test if var is unset

with bash:
  $ a="1"  ; [ -n "$a" ] && echo "a is not empty"
  a is not empty
  $ a=""    ; [ -n "$a" ] && echo "a is not empty"
  $ unset a ; [ -n "$a" ] && echo "a is not empty"
 and:
  $ unset a ; [ "${a+set}" = "set" ] && echo "a is set"
  $ a=""    ; [ "${a+set}" = "set" ] && echo "a is set"
  a is set
  $ a="1"   ; [ "${a+set}" = "set" ] && echo "a is set"
  a is set

IMO, [ -n "$var" ] is equivalent to [ "${var:+set} = "set" ].

The first form seems to be more readable and less error prone :)

PS: what is the simplest way to test if a variable is set?
-- 
Nekral