How to read properties valuues in for loop..?

rohithsharma · 03-31-2012, 10:24 PM

Hi guys,

Can someone help me for clearing below doubt please.Thanks in advance

"test.property" file contains
TEST_VALUES=A,B,C,D

"test.sh" test script file contain

source test.property
for value in $TEST_VALUES
do
echo Value:$value
done

Here , I want output as
Value:A
Value:B
Value:C

But I am getting output as
Value:A,B,C

suicidaleggroll · 03-31-2012, 10:38 PM

Can test.property be changed? The "for var in $array" syntax separates entries by spaces. Since your entries are separated by commas, you have three choices:

1) Modify test.property to look like TEST_VALUES="A B C D"
2) Modify your shell to separate by commas instead of (or in addition to) spaces
3) Use a different method of parsing the entries in TEST_VALUES

catkin · 04-01-2012, 12:17 AM

The behaviour is expected. There is no reason why for value in $TEST_VALUES bash should split the value of TEST_VALUES at each comma. If it did then any variable that happens to have commas in its value would be split!

This works, using shell parameter expansion to split $TEST_VALUES at the commas as desired. It will break if the strings between commas include spaces. That could be fixed by creating an array out of $TEST_VALUES but would be more complex.

Code:

#!/bin/bash

source test.property

for value in ${TEST_VALUES//,/ }
do
    echo Value:$value
done

Note: I have presumed that you did not want to drop the "D" value as stated in the OP.

David the H. · 04-01-2012, 11:05 AM

Please use [code][/code] tags around your code and data, to preserve formatting and to improve readability. Please do not use quote tags, colors, or other fancy formatting.

Yes, the problem here is due to word splitting. Since there are no spaces in the string, there's no splitting.

Two more options for you to consider.

1) Change the IFS value to a comma, so that it splits on them.

Code:

TEST_VALUES=A,B,C,D
IFS=','

for value in $TEST_VALUES ; do
	echo "Value:$value"
done

2) Use an array instead.

Code:

TEST_VALUES=( A B C D )


for value in "${TEST_VALUES[@]}" ; do
	echo "Value:$value"
done

I personally recommend #2, if possible. Arrays are designed for storing lists of values. If necessary, you can use IFS or catkin's technique above to split a scalar variable into an array.

Code:

TEST_VALUES=A,B,C,D

TEST_VALUES=( ${TEST_VALUES//,/ } )

#IFS=','			#alternately, using IFS
#TEST_VALUES=( $TEST_VALUES )

for value in "${TEST_VALUES[@]}" ; do
	echo "Value:$value"
done

See here for more string manipulation techniques:

http://mywiki.wooledge.org/BashFAQ/100]string manipulation

Finally:

QUOTE ALL OF YOUR VARIABLE SUBSTITUTIONS. You should never leave the quotes off a parameter expansion unless you explicitly want the resulting string to be word-split by the shell (globbing patterns are also expanded). This is a vitally important concept in scripting, so train yourself to do it correctly now. You can learn about the exceptions later.

http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes

( The above examples actually demonstrate one of the exceptions, but you should definitely quote the "echo" output variable. )

Clean, consistent formatting makes code readable and more easily debuggable. Indent all your sub-commands, and separate logical sections with whitespace. Add comments anywhere the code isn't completely obvious (and remember, what seems obvious to you now will not be a year or so down the line).

Many people also think that it's more readable to place the "do/then" keywords on the same line as the "for/while/until/if" keywords, as it more clearly separates the outside block from the inside block.

Code:

for var in fee fai foo fum ; do

	if [[ "$var" == "foo" ]]; then
		echo "Found 'foo'."
	fi

done

Environment variables are generally all upper-case. So while not absolutely necessary, it's good practice to keep your own user variables in lower-case or mixed-case, to help differentiate them.

rohithsharma · 04-10-2012, 01:27 AM

@suicidaleggroll,@catkin,@David the H

Thaks for your valuable knoledge sharing regarding shell string manipulation.

Thanks & Regards
Rohith Sharma K S