Need Help with getopts

paragkalra · 03-26-2011, 01:03 PM

Hi,

I am trying to use getopts on bash. Operating System is Mac 10.6.7

The aim is to test if an argument is provided with an option then it should take that or else if should take the default value defined in the script.

Currently if I provide the options with arguments it works but if I don't provide an argument, it takes next option as the argument for first option.

Here is the script:

$cat npc

Quote:

#!/bin/bash
user=parag
rh=redhat

while getopts "r:u:" os
do
case "$os" in
r) if [ $OPTARG ]; then oss=$OPTARG; else oss=$rh; fi ;;
u) if [ $OPTARG ]; then usr=$OPTARG; else usr=$user ; fi ;;
esac
done

echo $oss
echo $usr

Quote:

$ ./npc -r redhat -u pk
redhat
pk

Quote:

$./npc -r -u
-u

In last example can we make it print "redhat" and "parag"

carltm · 03-26-2011, 08:32 PM

Consider your logic. If someone uses "-r something", there
will always be an $OPTARG. So the test with the $OPTARG
value will always be true. If someone doesn't use the -r
option, that test will never run.

So you'd want to set your default values before reading
any input. Then if someone selects an option, assign the
new value to the variable.

Does this make sense?

unSpawn · 03-26-2011, 08:42 PM

...or maybe just parse args, throw an error and exit when OPTARG starts with a dash?:

Code:

[ "${OPTARG:0:1}" = "-" ] && { echo "A chair is still a chair
Even when there's no one sitting there
But a chair is not a house
And a house is not a home
(exiting)." >/dev/stderr; exit 127; }

dwhitney67 · 03-26-2011, 08:57 PM

Quote:

Originally Posted by unSpawn

...or maybe just parse args, throw an error and exit when OPTARG starts with a dash?:

Code:

[ "${OPTARG:0:1}" = "-" ] && { echo "A chair is still a chair
Even when there's no one sitting there
But a chair is not a house
And a house is not a home
(exiting)." >/dev/stderr; exit 127; }

No! Use carltm's advice. The point of getopt is that it will decide if there is an error on input. Otherwise, what is the point of using getopt if one must "parse" the input themselves?

unSpawn · 03-26-2011, 09:17 PM

Quote:

Originally Posted by dwhitney67

No! Use carltm's advice.

Ah, a connoisseur...

Code:

~]$ sh script.sh -r -u 
-u

..and with check

Code:

+check_opts() { [ "${OPTARG:0:1}" = "-" ] && { echo "Invalid arg, exiting." >/dev/stderr; exit 127; }; }
 while getopts "r:u:" os
 do
 case "$os" in
-r) if [ $OPTARG ]; then oss=$OPTARG; else oss=$rh; fi ;;
-u) if [ $OPTARG ]; then usr=$OPTARG; else usr=$user ; fi ;;
+r) if [ $OPTARG ]; then check_opts; oss=$OPTARG; else oss=$rh; fi ;;
+u) if [ $OPTARG ]; then check_opts; usr=$OPTARG; else usr=$user ; fi ;;

this becomes:

Code:

~]$ sh script.sh -r -u 
Invalid arg, exiting.