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Variable name change in a loop

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# 1  
Old 07-13-2010
Variable name change in a loop
I need to do something like this:
Code:
for I in var1 var2 var3 ; do
  $I = "Something calculated inside the loop"
done

Obviously it doesn't work...but is it possible doing that in other ways?

Thanks in advance.
# 2  
Old 07-13-2010
Code:
for I in var1 var2 var3 ; do
  eval $I=\"Something calculated inside the loop\"
done

$ echo $var1
Something calculated inside the loop

# 3  
Old 07-13-2010
Code:
for i in A B C
 do
 j=i ## save it in other variable
 echo $i
 i=XXX
 echo $i
 i=j ## reset back
 done

Output:
A
XXX
B
XXX
C
XXX

# 4  
Old 07-13-2010
Your example, scottn, works fine.
But my real case is a little bit more complicated...here a portion of it:
Code:
for I in UL_LAT UR_LAT LR_LAT LL_LAT UL_LON UR_LON LR_LON LL_LON ; do
            # Convert every value from 71 4 17.92 in 71.071644443
            DEGREES=$( echo ${I} | awk '{ print $1 }' )
            MINUTES=$( echo ${I} | awk '{ print $2 }' )
            SECOND=$(  echo ${I} | awk '{ print $3 }' )
            eval $I=$( echo "scale=9; ${DEGREES}+${MINUTES}/60+${SECOND}/3600" | bc )
        done

Executing that I obtain:
Code:
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: T
(standard_in) 1: syntax error
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: R
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: T
(standard_in) 1: syntax error
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: R
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: T
(standard_in) 1: syntax error
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: T
(standard_in) 1: syntax error
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: O
(standard_in) 1: illegal character: N
(standard_in) 1: syntax error
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: R
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: O
(standard_in) 1: illegal character: N
(standard_in) 1: syntax error
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: R
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: O
(standard_in) 1: illegal character: N
(standard_in) 1: syntax error
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: _
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: O
(standard_in) 1: illegal character: N
(standard_in) 1: syntax error

Any ideas?
# 5  
Old 07-13-2010
You have a few problems, not least this:

Code:
            # Convert every value from 71 4 17.92 in 71.071644443
            DEGREES=$( echo ${I} | awk '{ print $1 }' )
            MINUTES=$( echo ${I} | awk '{ print $2 }' )
            SECOND=$(  echo ${I} | awk '{ print $3 }' )

What does that comment mean, and where do those values come from?

DEGREES, MINUTES and SECOND are not set, so the bc is getting something like
Code:
+/60+/3600

which is obviously junk to it.
# 6  
Old 07-13-2010
"$I" is just the filenames so this is actually being piped to bc:
Code:
UL_LAT+/60+/3600

which is why reading down the right side of the errors gives you the filenames, minus the A, which it can apparently calculate. Learn something new every day.

Try this. It may not be the best approach but see if it works then we can go from there:
Code:
for I in $(cat UL_LAT UR_LAT LR_LAT LL_LAT UL_LON UR_LON LR_LON LL_LON)

# 7  
Old 07-14-2010
@ scottn:
The code I reported is a small piece of a 400 lines bash script, dealing with geographic coordinates manipulation.

In the version not looped, I've something like
Code:
DEGREES=$( echo ${UL_LAT} | awk '{ print $1 }' )
MINUTES=$( echo ${UL_LAT} | awk '{ print $2 }' )
SECOND=$(  echo ${UL_LAT} | awk '{ print $3 }' )
UL_LAT=$( echo "scale=9; ${DEGREES}+${MINUTES}/60+${SECOND}/3600" | bc )
                                                                        
DEGREES=$( echo ${UR_LAT} | awk '{ print $1 }' )
MINUTES=$( echo ${UR_LAT} | awk '{ print $2 }' )
SECOND=$(  echo ${UR_LAT} | awk '{ print $3 }' )
UR_LAT=$( echo "scale=9; ${DEGREES}+${MINUTES}/60+${SECOND}/3600" | bc )

...

and everything works fine. I would like to use a loop to use less lines of code.

@fubaya:
You're right: ${I} is substituted with my variable name and not with the variable content (which is for example "71 4 17.92" as reported in the comment above).
I cannot use "cat" as you suggested because ${I} are variables and not files.
There is a way to fix this?

- - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I solved using "variable indirect references", explained here:
Code:
# Convert every value from 71 4 17.92 in 71.071644443
for I in UL_LAT UR_LAT LR_LAT LL_LAT UL_LON UR_LON LR_LON LL_LON ; do
	# Indirect variable reference (parenthesis mean array)
	eval J=( \$${I} )
	eval ${I}=$( echo "scale=9; ${J[0]}+${J[1]}/60+${J[2]}/3600" | bc )
done

This is the shortest piece of code I can obtain: 4 lines instead of 16.
Thanks for your suggestions!
Last edited by canduc17; 07-14-2010 at 09:15 AM.. Reason: SOLVED!
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