i have a variable MYHOST that has my host name.depending on the host i have an array like A_<hostname>.Everytime i need to append the hostname to A_ to get the array.but in the shell script i am nt able to access the members of that array.
code of what i hav done:
export temp=A_$MYHOST
for d in $((temp))
do
...
...
...
done
now i get an arithmetic syntax error in the statement :"for d in $((temp))"
thanks in advance
for d in $temp
do
# your code here
done
Try that
If variable temp contains the name of your array, I think you want to expand it like this:
for d in "${!temp[@]}"
Each element of the array named by temp will be quoted.
The code as written by the OP creates a "normal" environment variable, so simply writing $temp allows the for loop to work with each word.
im not able to refer still getting the same error...
@....
for d in "${!temp[@]}"
still gets only a value 0 only and not the array values....
A_<hostname>=(1 2 3)
temp has A_<hostname> as its value....i now want to get the values from A_<hostname> array....
can you tell us the output of below comands.
echo $MYHOST
echo $A_MYHOST
$MYHOST
tragedy
$A_MYHOST
no value is displayed
niteesh that just means your MYHOST variable contains only 1 value namely "tragedy".
so your loop will only take 1 value as it contains only 1 value. if your variable has more than 1 value then your for loop will do more iterations.
for d in $temp #this temp has only 1value , the loop will run only one time
do
your code
done
actually see the situation is this....i agree that myhost has only one value but see the value of temp is
A_<the value in the myhost>
ie A_tragedy
A_tragedy is a predefined array now i need to access members of it
i am not sure, that i am actually getting what you are saying. you mean to say A_tragedy is a pre defined array.
can you show me the input of what exactly your array A_tragedy contains??
As in what are the input members and what is the exact thing you are looking for as an output.
export A_tragedy="1 2 3"
$MYHOST has tragedy
temp has value A_tragedy
now i want to access the members of array A_tragedy using the variable temp and print the array.
thanks in advance
echo $MYHOST >> TEMP
for word in ${TEMP}
do
##your code
done
try this and see if its working because as you are saying it should work
temp is a variable...i append content of $MYHOST to "A_" to get the name of the array,which i store in temp
so,
temp has A_tragedy....ie temp ="A_" appending to $MYHOST
$MYHOST=tragedy
You will have to use "eval", because variable expansion is done in one step in the shell and you need a two-time expansion: you need to expand "A_$MYHOST" to "A_HOSTNAME" and then "$A_HOSTNAME[<nr>]" to the value. See this post for a detailed explanation.
The following example code should tell you what you need:
typeset hostname="myserver"
typeset -i a_myserver[1]=1
typeset -i a_myserver[2]=2
typeset -i a_myserver[3]=3
typeset -i a_myserver[4]=4
typeset -i a_myserver[5]=5
# Display one value, showing the difference between "\\" and "\":
eval echo \\$a_\$hostname[1] is \${a_$hostname[1]}
# Cycle through all elements of the array: and store to a different array NewArr[]:
typeset iCnt=1
while [ $iCnt -le $(eval echo \${#$hostname[*]}) ] ; do
typeset NewArr[$iCnt]=$(eval echo \${$hostname[$iCnt]})
(( iCnt += 1 ))
done
I hope this helps.
bakunin
its working...thank you soo much....do u mind just explaining me what is happening with the command \${#$hostname[*]})
This tells you the number of elements in an array. I use it to end the loop at the appropriate array index. For example:
typeset array[1]="x"
typeset array[2]="y"
typeset array[3]="z"
echo ${#array[*]} # gives "3" as "array[]" contains 3 elements
typeset array[4]="u"
echo ${#array[*]} # gives now "4"
# like in the sample code above we introduce a further level of indirection:
typeset arr_name="array"
eval echo \${#$arr_name[*]} # will also yield "4"
You might see "${#array[@]}" instead of "${#array[*]}". Both these expressions will evaluate to the same value - the number of elements stored in the array.
I hope this helps.
bakunin