bash scripting

ninjafairy · 05-17-2011, 12:39 PM

im writing a bash script to dip my toe into programming but i need syntax help

pseudocode
x point
echo "do you accept (Y/N)"
if y continue
if n exit
else go to x point [or] (else ignore)

what bash commands would i use to make this happen

MensaWater · 05-17-2011, 12:48 PM

You might want to check out one of the numerous on line tutorials such as this one first:
http://linuxconfig.org/Bash_scripting_Tutorial

PTrenholme · 05-17-2011, 01:19 PM

First, your question should have been posted in the "Programming" forum, not here.
Second, bash, as a scripting language, executes a sequence of commands which, in principal, you could run from a command prompt.

So, the answer to your question is another question: What command(s) would you issue from a terminal (command-prompt window) to "move to a point?"

Note that, in your question, you have not told us what you want "moved" to the "point," nor have you told us what you want to do when it "gets" to the point.

Now I know that the above is not helpful, for which I apologize, so here's a guess: You're looking for a window manipulation method, and the "points" of which you speak are coordinates inside the window. If that's what you're look to accomplish from a command line, you need to be looking at a windowing system. For example, you could install the tool control language (tcl) and wish, and then use those commands to create and manipulate windows.

ninjafairy · 05-17-2011, 01:27 PM

ok ill repost in programming

this thread can be deleted

corp769 · 05-17-2011, 01:32 PM

Quote:

Originally Posted by ninjafairy

ok ill repost in programming

this thread can be deleted

This thread will not be deleted, it will only be moved to the appropriate forum. I will report it to be moved for you.

Cheers,

Josh

Nylex · 05-17-2011, 01:33 PM

Quote:

Originally Posted by ninjafairy

ok ill repost in programming

this thread can be deleted

Please don't do that; I've reported your thread to be moved to Programming. In future, if you've posted in the wrong place, just use the "Report" button to ask the moderators to move the thread for you.

ninjafairy · 05-17-2011, 01:36 PM

oh i did not know that will do from now on
thanks

corp769 · 05-17-2011, 01:41 PM

As far as your original post though, here is an excerpt from one of my scripts:

Code:

read -p "       place wlan0 into monitor mode? (yn) " answer
while true
do
  case $answer in
   [yY]* ) echo -e "\033[34m      ---placing wlan0 into monitor mode..."
           airmon-ng start wlan0
           break;;

   [nN]* ) break;;

   * )
  esac
done

I used that to ask a general yes or no question, and if Y or y is inputted, it executes airmon-ng. The tutorial that MensaWater posted is a good one to read and to understand and learn how to do bash scripting.

Cheers,

Josh

MTK358 · 05-17-2011, 07:42 PM

Quote:

Originally Posted by ninjafairy

im writing a bash script to dip my toe into programming but i need syntax help

pseudocode
x point
echo "do you accept (Y/N)"
if y continue
if n exit
else go to x point [or] (else ignore)

what bash commands would i use to make this happen

You don't use goto's in bash scripting.

Code:

if command
then
    this is run if "command" was successful
elif command
    this is run if the first command failed but this one succeeded
else
    this is run if none of the commands succeeded
fi

while command
do
    this is run over and over while "command" is successful. "command" is run before every iteration.
done

for myvar in list
do
    this code is run for every item of the list, where $myvar contains the current item
done

The "test" command (or it's alias, "[") is often used for if and while conditions. See "man test" for more info.

Ramurd · 05-18-2011, 08:59 AM

another approach is functions; Putting the stuff together would be

Code:

ask_question()
{
    valid="no"
    while [[ "$valid" != "no" ]]
    do
        echo -n "Can you give a valid answer? [y/n]: "
        read answer
        case $answer in
           [yY]*) valid="yes"; break;
           [nN]*) valid="yes"; break;
           *) valid="no"; break;
        esac
    done
}

while true
do
    ask_question
done

There are a few things to keep in mind:
- most likely the answer given in $answer is not carried over to the main part of your script; This is because in some cases bash spawns a sub-shell. I generally use Korn shell (ksh) to overcome that problem.
- a function must exist prior to calling it; so your functions are at the top of your script, the "body" at the bottom.

MTK358 · 05-18-2011, 09:51 AM

@Ramurd

Your script has two issues.

First, it should be "while [[ "$valid" = "no" ]]" instead of "while [[ "$valid" != "no" ]]".

Second, it appears that you take "Y" followed by any characters as a "yes". That means that if the users says "yffngfdgsnr", it will be taken as a "yes".

catkin · 05-18-2011, 10:00 AM

@Ramurd: the case statement in the while loop in the function breaks in every case so the loop never repeats ... but the while loop in the body repeats infinitely ...