conditional expressions (incompatible with ksh)

conditional expressions (incompatible with ksh)

[lists]

Hello,

So I have a ksh script which tests to see if a file exists like so:

     if [ -a file ]; then

This works correctly in both ksh and bash. However, in zsh (both the normal
mode, and the ksh compatible mode), the -a operator is only interpreted
as boolean AND, never as "file exists" in the appropriate context.

According to my "Unix in a Nutshell" book, -a is used for both operators,
and the shell needs to determine the correct use from context.

I realize that I could use [[ ]] instead of [ ] to work around this problem,
but the script needs to remain compatible with other shells, so this isn't
really a good option.

Any idea what the correct behavior should be?

mdr
-- 
Matthew D. Rench

Re: conditional expressions (incompatible with ksh)

[Will Yardley]

lists@pelennor.net wrote:
 
> So I have a ksh script which tests to see if a file exists like so:
> 
>      if [ -a file ]; then
 
> This works correctly in both ksh and bash. However, in zsh (both the
> normal mode, and the ksh compatible mode), the -a operator is only
> interpreted as boolean AND, never as "file exists" in the appropriate
> context.

perhaps someone can give a more detailed answer, but the '-a' operator
isn't mentioned in my bash scripting book, and i've never seen this
operator used (although i'll admit it works in bash and not in zsh).
how about using instead....

-e file exists
-f file exists and is a regular file (ie not a directory)
-s file exists and is not empty

i'd guess -f or -e is probably what you want and should work in bash,
ksh and zsh.

w

-- 
GPG Public Key:
http://infinitejazz.net/will/pgp/

Re: conditional expressions (incompatible with ksh)

[Clint Adams]

> Any idea what the correct behavior should be?

The POSIX-correct behavior should be to produce
unspecified results, since -a as a unary primary
is a bashism/kshism and not POSIX-compliant.

Use -e instead.

please take me off of this mailing list.

[Matthew Peter Lyon]

please take me off of this mailing list.