rmally read from the command-line arguments, when no such arguments are given. This is shown in the fo... n't exist or is null, print the error message. If no error message is given, print parameter null or n... rmally read from the command-line arguments, when no such arguments are given. This is shown in the fo... . One of the problems is that the man page offers no examples.
Here I'm going to show how to use some
]
# If a string has not been initialized, it has no defined value.
# This state is called "null" (not... rue
[ 1 -eq 2 ] && [ -n "`echo true 1>&2`" ] # (no output)
# ^^^^^^^ False condition. So far, everyt... te?
[[ 1 -eq 2 && -n "`echo true 1>&2`" ]] # (no output)
# No, that's not it.
# Apparently && and || "short-circuit" while -a and -o do not.
</code>
