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Top Forums Shell Programming and Scripting Use of double square brackets in ksh Post 302333012 by Scott on Friday 10th of July 2009 02:37:21 PM
Old 07-10-2009
To throw my 2 cents in!

I don't like [[ ]] partly for this reason:

Code:
if [[ $X -eq 1 ]]; then
  echo X is 1
else
  echo X is not 1
fi

If X is not 1 or X is not set the else part is executed (there's no error).

If X is not set and you use [ ], then...
Code:
if [ $X -eq 1 ]; then
  echo X is 1
else
  echo X is not 1
fi
./Test[1]: [: argument expected

I now know that X is not set. If I expect X to be set, then I should expect an error when it's not.

If it's OK for X not to be set, then I'd prefer to use:

Code:
if [ "$X" -eq 1 ]; then
  echo X is 1
else
  echo X is not 1
fi

At least then I'm aware of the fact, rather than blindly using [[ ]] which to me suggests that you really have no idea of the state of your variables.

Just my preference!

PS: I'm aware that didn't answer your question, but I think that was answered already...

Last edited by Scott; 07-10-2009 at 03:48 PM..
 

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SSH-KEYSIGN(8)						    BSD System Manager's Manual 					    SSH-KEYSIGN(8)

NAME
ssh-keysign -- ssh helper program for host-based authentication SYNOPSIS
ssh-keysign DESCRIPTION
ssh-keysign is used by ssh(1) to access the local host keys and generate the digital signature required during host-based authentication with SSH protocol version 2. ssh-keysign is disabled by default and can only be enabled in the global client configuration file /etc/ssh/ssh_config by setting EnableSSHKeysign to ``yes''. ssh-keysign is not intended to be invoked by the user, but from ssh(1). See ssh(1) and sshd(8) for more information about host-based authen- tication. FILES
/etc/ssh/ssh_config Controls whether ssh-keysign is enabled. /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys used to generate the digital signature. They should be owned by root, read- able only by root, and not accessible to others. Since they are readable only by root, ssh-keysign must be set-uid root if host- based authentication is used. /etc/ssh/ssh_host_dsa_key-cert.pub /etc/ssh/ssh_host_ecdsa_key-cert.pub /etc/ssh/ssh_host_ed25519_key-cert.pub /etc/ssh/ssh_host_rsa_key-cert.pub If these files exist they are assumed to contain public certificate information corresponding with the private keys above. SEE ALSO
ssh(1), ssh-keygen(1), ssh_config(5), sshd(8) HISTORY
ssh-keysign first appeared in OpenBSD 3.2. AUTHORS
Markus Friedl <markus@openbsd.org> BSD
December 7, 2013 BSD
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