Those of us who are used to command-line utilities, are used to passing arguments (aka parameters) to them: we don’t just run “ls“, we run “ls -ltSr“. So, how do we write a shell script which can take arguments?
There are two methods, and I will just deal with the simple approach, today. I’ll leave getopts for another day, when I have a little more time. The simple answer, is that, if we get called as “uppercase hello”, and we need to reply with “HeLlO”, then the script would look like this:
#!/bin/sh # uppercase ... convert alternate words to uppercase # note: there are many ways to do this (see previous posts) echo $1 | tr '[a-z]' '[A-Z]' echo $2 echo $3 | tr '[a-z]' '[A-Z]' echo $4 echo $5 | tr '[a-z]' '[A-Z]' echo $6
If we say uppercase a b c d e f,then it will reply with AbCdEf. Still, not much fun.
We can rewrite it like this, using the shift command, which discards the $1 and promotes $2:
#!/bin/sh echo $1 | tr '[a-z]' '[A-Z]' shift echo $1 shift echo $1 | tr '[a-z]' '[A-Z]' shift echo $1 shift echo $1 | tr '[a-z]' '[A-Z]' shift echo $1 shift
That way, we’re always dealing with $1. Otherwise, it’s just the same.
We can then put upper() into a function:
#!/bin/sh
upper()
{
echo $1 | tr '[a-z]' '[A-Z]'
}
for i in $*
do
upper $1
shift
echo $1
shift
done
This way, “$1″ is always the current argument. So “toupper.sh a b c d e f” will output “AbCdEf“.
