borne shell x=y, $x=7 echo $y, not set

[mcrobiej]

Ok this must be a quick one to answer

borne shell script:

x=y
$x=7

error
y=7

, how do i use the content of a variable as a name for a new variable?

also how do i return parameters from a function

i.e.

_read()
{
prompt=$1
temp=""

valid=0
while [ "$temp" = "" ]
do
echo "$1 : \c"
read temp
done
}

### main

option=_read "please enter your choice"

#?

 

[bjverzal]

x=7
y=$x
echo $x
7
echo $y
7

======================
Read() {
echo $1
read fooo
}
Read "This is a test"
echo $fooo



Bill.

 

[mcrobiej]

Bill, not quite,

you have turned it around to make it work !!

let me add more info

variablename=mode

now I want to set the variable mode to manual, but this does not work.

$variablename=manual

. You also have done the function returning using a global variable, I already have it working this way but it is messy.

_read()
{
prompt=$1
temp=""

valid=0
while [ "$temp" = "" ]
do
echo "$1 : \c"
read temp
done
}

####

_read "> Function (start/stop/exit)"
operation=$temp
_read "> Mode(Manual/automatic)"
mode=$temp


#####

there must be a nicer way? I want to pass a variable back,

 

[bjverzal]

You'll be hard pressed to do the first stop of this. As for the second step, the only way to do it is to set a global variable to the value of a private variable. That is by definition what a private variable is.

Bill.

 

[RobJordan]

I have only been able to do this by using an array.

Here's an example.

You could echo your dynamic names and redirect
them into the TMP_LIST file.
You could then read them from the array
and set values for them.


#!/usr/bin/ksh
TMP_LIST=/tmp/TMP_LIST.$$ # Create_Array reads from this file to create array

Create_Array () # requires one argument for ARRAY_NAME and reads from TMP_LIST
{
ARRAY_NAME=$1
ITEM_NUMBER=1 # start item number at 1
cat ${TMP_LIST}.${ARRAY_NAME}|while read ARRAY_ITEM
do
echo "...\c"
eval "${ARRAY_NAME}[${ITEM_NUMBER}]=\"${ARRAY_ITEM}\"" # read from $TMP_LIST and add ite
m to array
ITEM_NUMBER=`expr $ITEM_NUMBER + 1` # increment item number by one
done
> $TMP_LIST.$ARRAY_NAME # clear TMP_LIST
# > ARRAY_ITEM
}

Display_Array () # list contents of the array on screen - this can be used in conjunction with | or >>
{
ARRAY_NAME=$1
DISPLAY_COUNTER=1
ARRAY_STRING="\${#$ARRAY_NAME[*]}"
eval "ARRAY_ITEM_COUNT=$ARRAY_STRING"

until [ $DISPLAY_COUNTER -eq $ARRAY_ITEM_COUNT ] # print array
do
ARRAY_STRING="\${$ARRAY_NAME[$DISPLAY_COUNTER]}"
eval "ARRAY_ITEM=$ARRAY_STRING"
echo $ARRAY_ITEM
DISPLAY_COUNTER=`expr $DISPLAY_COUNTER + 1`
done
}

Example:
ps -ef >> $TMP_LIST

Create_Array ps

Display_Array ps

for your progam just substitute the ps -ef
with whatever method you are using to
create the dynamic variable names.

Robert

Robert G. Jordan

Robert@JORDAN2000.com
Unix Admin, United Airlines

 

[ElgisRamon]

I think you want a reference to a variable onto another variable... try
[tt]
${$var}
[tt]
With the name inside $var variable.
I hope it works...
Unix was made by and for smart people.

 

[RobJordan]

EglisRamon, if you can get this to work,
that would be great.I've always been
stumped with this issue.

Robert

Here's script I wrote for a test
and the ouput is listed below.

#!/usr/bin/sh
# virtual_var script
# attempt to create a virtual variable

VARIABLE_NAME=MODE

# ${$var}

${$VARIABLE_NAME}=manual # this command doesn't seem to work

echo "Variable Name: $VARIABLE_NAME"
# output I'm hoping for: Variable Name: MODE

echo "$VARIABLE_NAME = ${$VARIABLE_NAME}"
# output I'm hoping for: MODE = manual

----OUTPUT--------------------
# ./virtual_var
./virtual_var[7]: ${$VARIABLE_NAME}=manual: The specified substitution is not valid for this command. Robert G. Jordan

Robert@JORDAN2000.com
Unix Admin, United Airlines

 

[Guest_imported]

hi,
part of the job could be done using 'eval'
in Bourne Shell:
x=y
eval $x=7
So far it will work; when you type 'echo $y', you will get '7'. But i do not know how to replace 'echo $y' by something containing '$x'.
Someone else has an idea?
regards