ksh parsing arguments in a string rather than from the cmdln
Hi. I have a piece of code that reads and parses command line options. I'd like to alter it slightly to read from a string (that's set elsewhere in the script) rather than directly from the command line (arg). Can somebody show me how to do this? Many thanks.
My code is as follows:
Code:
typeset flags_args=''
for arg; do
case $arg in
-version ) flags_args="${flags_args} -t" ;;
-host ) flags_args="${flags_args} -r" ;;
-debug ) flags_args="${flags_args} -d" ;;
* ) flags_args="${flags_args} $arg" ;;
esac
done
set -- ${flags_args}
while getopts :t:r:d args; do
case $args in
t) typeset VERSION="$OPTARG" ;;
r) typeset HOST="$OPTARG" ;;
d) typeset DEBUG="true"; typeset DEBUG="DEBUG" ;;
*) print "Invalid option specified." ;;
esac
done
shift $((OPTIND-1));
Instead of reading the arguments from command line I'd like the code to read from the following variable that's set inside the KSH script:
Hi. I have a piece of code that reads and parses command line options. I'd like to alter it slightly to read from a string (that's set elsewhere in the script) rather than directly from the command line (arg). Can somebody show me how to do this? Many thanks.
My code is as follows:
Code:
typeset flags_args=''
for arg; do
case $arg in
-version ) flags_args="${flags_args} -t" ;;
-host ) flags_args="${flags_args} -r" ;;
-debug ) flags_args="${flags_args} -d" ;;
* ) flags_args="${flags_args} $arg" ;;
esac
done
set -- ${flags_args}
while getopts :t:r:d args; do
case $args in
t) typeset VERSION="$OPTARG" ;;
r) typeset HOST="$OPTARG" ;;
d) typeset DEBUG="true"; typeset DEBUG="DEBUG" ;;
*) print "Invalid option specified." ;;
esac
done
shift $((OPTIND-1));
Instead of reading the arguments from command line I'd like the code to read from the following variable that's set inside the KSH script:
Code:
STR="-version 99 -host testhost "
or
Code:
STR="-version 99 -host testhost -debug"
Many versions of the Korn shell include a getopts that supports both long options and short options (although support for long options isn't always mentioned in the ksh man page). If you could introduce your long options with -- instead of a single -, you might want to try the following replacement for your code:
Code:
while getopts ':t:(version)r:(host)d(debug)' args; do
case $args in
t) typeset VERSION="$OPTARG" ;;
r) typeset HOST="$OPTARG" ;;
d) typeset DEBUG="DEBUG" ;;
*) print "Invalid option specified." ;;
esac
done
shift $((OPTIND-1));
printf 'DEBUG has been set to "%s"\n' "$DEBUG"
printf 'HOST has been set to "%s"\n' "$HOST"
printf 'VERSION has been set to "%s"\n' "$VERSION"
and see what happens when you invoke it with:
Code:
script_name --version 99 --host=testhost
and:
Code:
script_name -t 98.6 -rmyhost --debug
When I try the above two commands with ksh on macOS High Sierra (version 10.13.1), I get the output:
Code:
DEBUG has been set to ""
HOST has been set to "testhost"
VERSION has been set to "99"
and:
Code:
DEBUG has been set to "DEBUG"
HOST has been set to "myhost"
VERSION has been set to "98.6"
Thanks Don. But how do I read the parameters into that case statement from a variable set within the script rather than the command line?
You can also use a subfunction to parse the command line and feed it the string:
Code:
parse_cmd ()
{
while getopts :t:r:d args; do
case $args in
t) typeset VERSION="$OPTARG" ;;
r) typeset HOST="$OPTARG" ;;
d) typeset DEBUG="true"; typeset DEBUG="DEBUG" ;;
*) print "Invalid option specified." ;;
esac
done
shift $((OPTIND-1));
return 0
}
...
# main()
STR="<your arguments here in the same form as parameters from stdin>"
parse_cmd $STR # process opts and args from STR
parse_cmd $* # process opts and args from stdin
exit 0
Note that if you use a subfunction like above you need to get the parsed values out of the function somehow, because the variables in it are now local to the function.
You can also use a subfunction to parse the command line and feed it the string:
Code:
parse_cmd ()
{
while getopts :t:r:d args; do
case $args in
t) typeset VERSION="$OPTARG" ;;
r) typeset HOST="$OPTARG" ;;
d) typeset DEBUG="true"; typeset DEBUG="DEBUG" ;;
*) print "Invalid option specified." ;;
esac
done
shift $((OPTIND-1));
return 0
}
...
# main()
STR="<your arguments here in the same form as parameters from stdin>"
parse_cmd $STR # process opts and args from STR
parse_cmd $* # process opts and args from stdin
exit 0
Note that if you use a subfunction like above you need to get the parsed values out of the function somehow, because the variables in it are now local to the function.
I hope this helps.
bakunin
Hi bakunin,
Note that typeset is not in the standards and the way it behaves varies some between shells. In bash declaring a variable with local or with typeset makes the variable definition have a scope that is local to the function and values assigned to such variables are not visible when the function returns to its caller. But, a variable that is not declared with local nor with typeset has a global scope and if such a variable is assigned a value inside a function, the value assigned in the function will still be visible when the variable is expanded outside of the function.
In ksh, declaring a variable with typeset in a function does not give it a local scope; it has a global scope. The ksh command language does not have a local keyword or built-in function.
The values assigned to VERSION, HOST, and DEBUG in the function parse_cmd can be found after parse_cmd completes by just expanding those variables with $VERSION, $HOST, and $DEBUG.
Note that I removed the 1st assignment to DEBUG. I don't see any reason to assign it the value TRUE and then immediately assign another value (DEBUG) to it.
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11-15-2017
