I need some help taking a selection from a command and adding part of the output to an array.
In general: to get qualified help with SHELL PROGRAMMING problems it usually helps to tell WHICH SHELL you are talking about. Sorry, but my crystal ball is in repair right now and mind reading is not part of the job description.
I suggest you read up on the select-command which many shells offer. It should do exactly what you have in mind. Have a look at the documentation of your shell and if it doesn't have it then report back - and tell us which shell that is.
Could you confirm your belief that "it does look like something that could solve this", e.g. by trial and error? That were a possible (if not the usual) approach when encountering something new.
Howsoever, here's a small example how you could proceed. Unfortunately, I had to go through a TMP file, as piping the sed result directly into readarray failed, although its man page says: "Read lines from the standard input into the indexed array variable array"
Try and comment back
Just in case it helps here is my bad attempt that doesn't work. I thought posting my bad attempt might confuse the situation as I'm trying to find a simpler solution thats easier to replicate for other searches.
Code:
#!/bin/bash
q=1
for z in `awless -l list routetables --columns ID,NAME,VPC --filter VPC=vpc-00xxxxxxxxxxxe52 |\
awk '
/\| vpc/ && NF == 4 { print $2 ":No_Label" }
/\| vpc/ && NF == 5 { print $2 ":" $4 }
'`
do
array3[$q]=`echo $z | awk -F: ' { print $2 } '`
array4[$q]=`echo $z | awk -F: ' { print $1 } '`
echo " $q. $z" ; q=$(($q + 1))
done
read selection2
if [[ $selection2 =~ ^[0-9][0-9]*$ ]] ; then
echo
else
echo "That selection was not valid"
exit
fi
if [ ${array3[$selection2]} ] ; then
arrayvar3="${array3[$selection2]}"
arrayvar4="${array4[$selection2]}"
echo "Thank you for your selection. I will use this for my script... $arrayvar3 $arrayvar4"
echo ""
echo "Processing....."
else
echo "That selection was not valid"
exit
fi
First off: thank you for posting your script. It is a lot easier (and perhaps much better for you) to explain to you what you did wrong than to just envision a solution which yu don't understand where it comes from. It will not confuse the situation but in fact help clarify it. We do not want to solve your problem - we want to enable you to solve it on yourself.
Quote:
Originally Posted by bignellrp
Just in case it helps here is my bad attempt that doesn't work. I thought posting my bad attempt might confuse the situation as I'm trying to find a simpler solution thats easier to replicate for other searches.
Code:
#!/bin/bash
q=1
for z in `awless -l list routetables --columns ID,NAME,VPC --filter VPC=vpc-00xxxxxxxxxxxe52 |\
awk '
/\| vpc/ && NF == 4 { print $2 ":No_Label" }
/\| vpc/ && NF == 5 { print $2 ":" $4 }
'`
do
array3[$q]=`echo $z | awk -F: ' { print $2 } '`
array4[$q]=`echo $z | awk -F: ' { print $1 } '`
echo " $q. $z" ; q=$(($q + 1))
done
read selection2
if [[ $selection2 =~ ^[0-9][0-9]*$ ]] ; then
echo
else
echo "That selection was not valid"
exit
fi
if [ ${array3[$selection2]} ] ; then
arrayvar3="${array3[$selection2]}"
arrayvar4="${array4[$selection2]}"
echo "Thank you for your selection. I will use this for my script... $arrayvar3 $arrayvar4"
echo ""
echo "Processing....."
else
echo "That selection was not valid"
exit
fi
Let us first sum up the goal: you want to create a selection menu from the output of a program. The output is roughly a table and each line will be a possible selection, yes?
Now, let us examine the description of the selection-keyword. Here it is (taken from my system, a Linux):
Code:
select name [ in word ] ; do list ; done
The list of words following in is expanded, generating a list of
items. The set of expanded words is printed on the standard
error, each preceded by a number. If the in word is omitted,
the positional parameters are printed (see PARAMETERS below).
The PS3 prompt is then displayed and a line read from the stan-
dard input. If the line consists of a number corresponding to
one of the displayed words, then the value of name is set to
that word. If the line is empty, the words and prompt are dis-
played again. If EOF is read, the command completes. Any other
value read causes name to be set to null. The line read is
saved in the variable REPLY. The list is executed after each
selection until a break command is executed. The exit status of
select is the exit status of the last command executed in list,
or zero if no commands were executed.
So we first have to create a list of words. You already did this by creating the array. Let us set aside your problem for a moment to get us acquainted with the select-keyword. Here it is:
Code:
#! /bin/bash
arr[1]="apples"
arr[2]="bears"
arr[3]="peaches"
arr[4]="oranges"
selection=""
select selection in ${arr[@]} ; do
echo "You selected $selection"
done
echo "here is the end of the program"
exit 0
Try that out on your own system. (Really! Try it! Don't just take my word for it.)
Now what did you find? First, the selection works smoothly. As long as you enter "1", "2", "3" or "4" everything works fine. What happens when you enter "0" or "17" or "blabla"? And how is the selection loop left? You probably figured out that you can use Ctrl-C to exit, but that is not a nice way to leave it. We would rather have something like "Press 1-4 for select a fruit or x to exit", yes?
Also there is this ridiculous prompt: Shouldn't there be something like, "Press..." as i said above, rather than "#?"? Let us start with this. There was this part of the documentation:
Quote:
The PS3 prompt is then displayed and a line read from the standard input.
So, we have to set the PS3 prompt (shell has 4 different prompts for certain situations. We usually see PS1, which it displays when waiting for the use to enter a command, but here PS3 is used) and we do that right before the start of the selection:
Code:
#! /bin/bash
arr[1]="apples"
arr[2]="bears"
arr[3]="peaches"
arr[4]="oranges"
selection=""
PS3="Enter 1-4 to select a fruit or x to exit => "
select selection in ${arr[@]} ; do
echo "You selected $selection"
done
echo "here is the end of the program"
exit 0
Better, yes? But we should have a reaction of some sort when the user pressed a non-existing item, like "5" or "0" or "blabla". So we have to put some logic into the loop to react to that. Since we might need several cases we do not use if, but a case..esac:
Code:
#! /bin/bash
arr[1]="apples"
arr[2]="bears"
arr[3]="peaches"
arr[4]="oranges"
selection=""
PS3="Enter 1-4 to select a fruit or x to exit => "
select selection in ${arr[@]} ; do
case "$selection" in
"")
echo "You selected a non-existing item"
;;
*)
echo "You selected $selection"
;;
esac
done
echo "here is the end of the program"
exit 0
Why did this work? because the documentation said:
Quote:
If the line consists of a number corresponding to one of the displayed words, then the value of name is set to that word. [...] Any other value read causes name to be set to null.
That means, enter 1-4 and the value of "$selection" is set to the first-fourth element of our array. Enter any other value and the value of selection is set to "" (the null string). This is what we checked in the first case-branch, any other value means some "legal" value was entered.
We still did not implement a means of leaving the loop so we tackle this as next: we can simply add a special item to the array which selection causes the loop to be left:
Code:
#! /bin/bash
arr[1]="apples"
arr[2]="bears"
arr[3]="peaches"
arr[4]="oranges"
arr[5]="EXIT"
selection=""
PS3="Enter 1-4 to select a fruit or 5 to exit => "
select selection in ${arr[@]} ; do
case "$selection" in
"")
echo "You selected a non-existing item"
;;
"EXIT")
echo "You are leaving the loop."
break
;;
*)
echo "You selected $selection"
;;
esac
done
echo "here is the end of the program"
exit 0
Notice that now, for a change, the line i put in next to the last line "here is the end of the program" was executed for the first time. We really and correctly left the program. It is also time now to make the whole thing a bit more "dynamic": right now, if we add another item, we would have to change not only the array and the number of the "EXIT" item, but also the PS3-prompt. We will make these to adjust automatically:
The number of elements in an array is in a variable expansion: "${#<arrayname>[@]}". So, to automatically add the "EXIT" item as the last item of the array we do:
Notice that "((${#arr[@]}+1))" will always evaluate to the number of array elements plus 1. So now, it evaluates to "5", but if i remove the line with the oranges it would evaluate to "4" and if i would add a line it would evaluate to "6". We do something similar to the PS3 prompt:
Code:
PS3="Enter 1-$((${#arr[@]}-1)) to select a fruit or ${#arr[@]} to exit => "
Notice that since the EXIT-selection will have a varying index but always the same value (the string "EXIT") we do not need to change the loop itself. So here is our script, were you can remove or add items to the initial array without changing anything else:
Code:
#! /bin/bash
arr[1]="apples"
arr[2]="bears"
arr[3]="peaches"
arr[4]="oranges"
arr[((${#arr[@]}+1))]="EXIT"
selection=""
PS3="Enter 1-$((${#arr[@]}-1)) to select a fruit or ${#arr[@]} to exit => "
select selection in ${arr[@]} ; do
case "$selection" in
"")
echo "You selected a non-existing item"
;;
"EXIT")
echo "You are leaving the loop"
break
;;
*)
echo "You selected $selection"
;;
esac
done
echo "here is the end of the program"
exit 0
I will stop here now, because you are sure anxious to try your newfound toy and play around with it. I also suggest that when you write scripts you do the indenting like i do and not like you did. Experience shows that it is easier to discern the program flow and the structure that way.
Have fun and if you still have questions don't hesitate to ask.
I hope this helps.
bakunin
These 3 Users Gave Thanks to bakunin For This Post:
Wow. Thanks so much bakunin. You are certainly right that it is better to "teach a man to fish". I struggled with this for hours before i posted as it was hard finding something on google that was relevant enough to my problem to learn from. So now not only am i one step closer to resolving my problem i have learned a lot more.
I'll have a play and let you know how i get on.
------ Post updated at 05:24 PM ------
Having much more fun now i know how the array works, but I'm struggling to get the row to display as a whole selection. The array is splitting all the individual items into options.
options=( $(awless -l list routetables --columns ID,NAME,VPC --filter VPC=vpc-0025xxxxxxxe52 | grep rtb | sed 's/|//g') )
selection=""
options[((${#options[@]}+1))]="EXIT"
selection=""
PS3="Enter 1-$((${#options[@]}-1)) to select an item or ${#options[@]} to exit => "
#PS3="Select an item or 5 to exit => "
select selection in ${options[@]} ; do
case "$selection" in
"")
echo "You selected a non-existing item"
;;
"EXIT")
echo "You are leaving the loop."
break
;;
*)
echo "You selected $selection"
;;
esac
done
echo "here is the end of the program"
exit 0
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10-05-2018
