Tilted Forum Project Discussion Community - Shell scripting help (bash)

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" :rolleyes: