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Shell Programming and Scripting

Variable variables

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# 1  
Old 04-05-2013
Variable variables
Hello,

Can you please help here?
Code:
DAY=$1

MONTH_MONDAY_YEAR = 1 2 3 4



	for i in ${MONTH_${DAY}_YEAR}
	do
		echo ${i}
	done


./test.sh MONDAY
./test.sh: line 3: MONTH_MONDAY_YEAR: command not found
./test.sh: line 10: ${MONTH_${DAY}_YEAR}: bad substitution
# 2  
Old 04-05-2013
Hi, there are some errors
1) assegments without spaces
Code:
MONTH_MONDAY_YEAR=1 2 3 4

2) this sintax is not possible
Code:
${MONTH_${DAY}_YEAR}

But the question is: what is the expected result?
# 3  
Old 04-05-2013
Like to know is there an alternative for
Code:
${MONTH_${DAY}_YEAR}

if it is not possible.

Ideally I like to use the value of MONTH_MONDAY_YEAR in the for loop

Code:
for i in ${MONTH_${DAY}_YEAR}

# 4  
Old 04-05-2013
Check this out

LINK
# 5  
Old 04-05-2013
Thanks to PikK45: then I suggest this code
Code:
DAY=$1
MONTH_MONDAY_YEAR="1 2 3 4"
eval echo \$MONTH_${DAY}_YEAR |tr -s ' ' '\n'| while read i
do
echo ${i}
done

# 6  
Old 04-05-2013
A modern shell will let you dereference a string with ${!...}

You must assign the string first, you can't embed the string inside the {}

Code:
STR="${MONTH}_${DAY}_${YEAR}"

echo "${!STR}"

This User Gave Thanks to Corona688 For This Post:
vino_hymi
# 7  
Old 04-05-2013
@Corona688 it's fantastic:
Code:
DAY=$1
MONTH_MONDAY_YEAR="1 2 3 4"
STR="MONTH_${DAY}_YEAR"
for i in ${!STR}
do
echo ${i}
done

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