Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
MINPARAMS=10
echo
echo "The name of this script is \"$0\"."
# Adds ./ for current directory
echo "The name of this script is \"`basename $0`\"."
# Strips out path name info (see 'basename')
echo
if [ −n "$1" ]
# Tested variable is quoted.
then
echo "Parameter #1 is $1" # Need quotes to escape #
fi
if [ −n "$2" ]
then
echo "Parameter #2 is $2"
fi
if [ −n "$3" ]
then
echo "Parameter #3 is $3"
fi
# ...
if [ −n "${10}" ] # Parameters > $9 must be enclosed in {brackets}.
then
echo "Parameter #10 is ${10}"
fi
echo "−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−"
echo "All the command−line parameters are: "$*""
if [ $# −lt "$MINPARAMS" ]
then
echo
echo "Give me at least $MINPARAMS command−line arguments!"
fi
echo
exit 0
The bracket notation for positional parameters leads to a fairly simply way of referencing the last
argument passed to a script on the command line. This also requires indirect referencing.
args=$#
# Number of args passed.
lastarg=${!args} # Note that lastarg=${!$#} doesn't work.
Some scripts can perform different operations, depending on which name they are invoked with. For
this to work, the script needs to check $0, the name it was invoked by. There must also exist symbolic
links to all the alternate names of the script.
If a script expects a command line parameter but is invoked without one, this may
cause a null variable assignment, generally an undesirable result. One way to prevent
Chapter 4. Introduction to Variables and Parameters 29