Hi,
I have the following problem:
I would like a script to decide on a commandline that should be executed.
This descision is based on the arguments passed to the script.
The possibilities for the commandline-to-be-executed are fixed, and declared at the beginning of the script.
script flow:
- declaration of possible command calls (CALL_A and CALL_B , see below)
- case statement on the argument $1 that either sets (CALL=CALL_A or CALL=CALL_B)
- exectute CALL
This works fine in most cases, except when CALL_A or CALL_B use an output re-director.
If I declare CALL_A="ls -al >test.txt"
then ls is executed with "-al" and ">test.txt" as parameters, causing an error because ls can't find the file ">test.txt".
I realize this might sound fuzzy, so I wrote 2 scripts as an example:
Script 1:
(echo's all arguments that were passed to it. this allows you to see how the commandline was interpreted.)
Code:
#!/bin/bash
#prints the first 4 arguments that are passed to it. $0 is the name of the script!
#
if [ -n $0 ]
then
echo "arg 0: $0"
fi
if [ -n $1 ] then
echo "arg 1: $1"
fi
if [ -n $2 ] then
echo "arg 2: $2"
fi
if [ -n $3 ] then
echo "arg 3: $3"
fi
if [ -n $4 ] then
echo "arg 4: $4"
fi
Script 2:
(This script is giving me troubles, it runs the above script with normal or redirected output commandlines. The second type
should echo into a file and not on screen.)
Code:
## testing script
#command to run:
CALL_A="./arg_check 1st 2nd 3rd 4th"
CALL_B="./arg_check 1st >result.txt"
#select command based on argument, or present helpful message:
if [ -n "$1" ] #test wether $1 has been initialized
then
case "$1" in
"a" ) CALL=$CALL_A ;;
"b" ) CALL=$CALL_B ;;
* ) echo "Duh, enter a or b"
exit 1 ;;
esac
else
echo "Enter a or b as an argument please"
exit 1;
fi
#call the chosen command:
$CALL
If you copy/save these scripts as "arg_check" and "testscript" respectively, you can run "./testscript a" or "./testscript b" to see the results. (remember to chmod +x them both)
You'll notice that the CALL_B commandline if executed directly on the prompt behaves as expected: the output of "arg_check a" is redirected to "result.txt"
I'd REALLY like to know what in the second script I should change to get the expected result: i.e.
./testscript a results in output to screen
./testscript b results in output to file
Note: It's not really an option to remove the declarations and "$CALL" statement, and move the commandlines directly into the case statement (which would work irf you used "backticks": `) as the script this is meant for uses several sources and checks to build and conditionally execute the commands.
2nd note: I'm quite new to shell scripting so if you have any tips, please post them! Also if this code is laughable: any constructive comments are really appreciated!
EDIT: edited because the "submit" button is a lot more attractive than the one for "preview"
