declare -a index=(0 1 2 3 4);
declare -a animals=(dog cat horse penguin cow);
declare -a fruits=(orange apple grapes peach mango);
declare -a drinks=(juice milk coffee tea coke);
declare -a cities=(toronto paris london glasgow sydney);
declare -a countries=(canada france england scotland australia);
declare -a all=(animals fruits drinks cities countries);
for i in "${index[@]}" ; do
echo ${i};
animals="${animals["${i}"]}";
echo $animals;
fruits="${fruits["${i}"]}";
echo $fruits;
drinks="${drinks["${i}"]}";
echo $drinks;
cities="${cities["${i}"]}";
echo $cities;
countries="${countries["${i}"]}";
echo $countries;
done
And this is the output:
Code:
0
dog
orange
juice
toronto
canada
1
cat
apple
milk
paris
france
2
horse
grapes
coffee
london
england
3
penguin
peach
tea
glasgow
scotland
4
cow
mango
coke
sydney
australia
Because my actual script has more arrays to loop through and I'll be adding more as time goes on, I came up with an 'all' array that has the array names in it. Then I attempted to loop through each array as such:
Code:
for i in "${index[@]}" ; do
echo ${i};
for j in "${all[@]}" ; do
echo ${!j[${i}]};
done
done
But this time I'm only getting items at index 0, as per the output below:
Code:
0
dog
orange
juice
toronto
canada
1
2
3
4
abc@xyz$
I've been struggling with this one for a while now, and I'm not entirely sure what I'm trying to accomplish is possible with Bash. Any help is appreciated!
I don't know if you can do what you're trying to do with bash, but you can do it with a 1993 or later version of ksh by using a name reference variable. You can't do it quite the way you were trying to do it because you can't currently create arrays of nameref variables, but the following seems to produce results similar to what I think you were trying to do:
Code:
#!/bin/ksh
animals=(dog cat horse penguin cow)
fruits=(orange apple grapes peach mango)
drinks=(juice milk coffee tea coke)
cities=(toronto paris london glasgow sydney)
countries=(canada france england scotland australia)
sparse[1]=first
sparse[10]=tenth
sparse[33]='thirty-third'
sparse[100]=hundredth
typeset -A associative
associative["a b"]='A B'
associative["x y z"]='X Y Z'
associative["SomeOtherString"]='Anything you might want'
arrays=(animals fruits drinks cities countries sparse associative)
typeset -n arrayname
for arrayname in "${arrays[@]}"
do for subscript in "${!arrayname[@]}"
do printf '%s[%s]=%s\n' "${!arrayname}" "$subscript" "${arrayname[$subscript]}"
done
done
which produces the output:
Code:
animals[0]=dog
animals[1]=cat
animals[2]=horse
animals[3]=penguin
animals[4]=cow
fruits[0]=orange
fruits[1]=apple
fruits[2]=grapes
fruits[3]=peach
fruits[4]=mango
drinks[0]=juice
drinks[1]=milk
drinks[2]=coffee
drinks[3]=tea
drinks[4]=coke
cities[0]=toronto
cities[1]=paris
cities[2]=london
cities[3]=glasgow
cities[4]=sydney
countries[0]=canada
countries[1]=france
countries[2]=england
countries[3]=scotland
countries[4]=australia
sparse[1]=first
sparse[10]=tenth
sparse[33]=thirty-third
sparse[100]=hundredth
associative[SomeOtherString]=Anything you might want
associative[a b]=A B
associative[x y z]=X Y Z
These 2 Users Gave Thanks to Don Cragun For This Post:
Then I attempted to loop through each array as such:
Code:
for i in "${index[@]}" ; do
echo ${i};
for j in "${all[@]}" ; do
echo ${!j[${i}]};
done
done
But this time I'm only getting items at index 0, as per the output below:
The underlying problem is: arrays in bash (and ksh88 as well) are ONE-dimensional. Therefore, you can create a variable holding a one-dimensional array, but you can't put other array variables as elements into this array.
You could use the following workaround, but i strongly suggest you don't. Stretching the limits of what can be done is fun and helps learning the trade, but you shouldn't put circus tricks into production code. So, with this (rather big) grain of salt, here it goes:
Variables are evaluated always in the same step and all at the same time, which is why you cannot do things like this:
This would rely on "${selector}" to be evaluated first and only then the resulting "${xfoo}" to be evaluated again. But, as i said, this is not the case and therefore this will fail.
There is one remedy for that, though: the keyword eval. eval starts the evaluation process again and this way you get (among other things) a second evaluation phase for your variables:
The same way you can create sort-of two-dimensional arrays by using this mechanism:
Code:
arr1[1]="arr1.1"
arr1[2]="arr1.2"
arr1[3]="arr1.3"
arr1[4]="arr1.4"
arr2[1]="arr2.1"
arr2[2]="arr2.2"
arr2[3]="arr2.3"
arr2[4]="arr2.4"
arr3[1]="arr3.1"
arr3[2]="arr3.2"
arr3[3]="arr3.3"
arr3[4]="arr3.4"
for i in 1 2 3 ; do
for j in 1 2 3 4 ; do
eval echo \${arr${i}[$j]}
done
done
But again: avoid eval like the plague and if you have to use it this is usually indicative that you better search for an alternative. As a show-off of skill, though, it is pretty cool. No?
You can't do it quite the way you were trying to do it because you can't currently create arrays of nameref variables
Quote:
The underlying problem is: arrays in bash (and ksh88 as well) are ONE-dimensional. Therefore, you can create a variable holding a one-dimensional array, but you can't put other array variables as elements into this array.
I had a feeling I'd get that kind of answer but was still hoping for a syntax fix
Quote:
This would rely on "${selector}" to be evaluated first and only then the resulting "${xfoo}" to be evaluated again. But, as i said, this is not the case and therefore this will fail.
Yes that's exactly what I wanted, evaluate "${selector}" first then "${xfoo}" :S
Because my script is pretty much done and I've never written ksh before, I guess I'll just stick to adding array names manually as I go. At least this implementation works in bash.
Thanks!
---------- Post updated at 12:11 PM ---------- Previous update was at 12:09 PM ----------
Quote:
As a show-off of skill, though, it is pretty cool. No?
Don't despair - typeset -n is understood by bash as well:
Code:
typeset -n j
for i in "${index[@]}" ; do echo ${i}; for j in "${all[@]}" ; do echo ${!j}, ${j[$i]}; done; done
0
animals, dog
fruits, orange
drinks, juice
cities, toronto
countries, canada
1
animals, cat
fruits, apple
drinks, milk
cities, paris
countries, france
2
animals, horse
fruits, grapes
drinks, coffee
cities, london
countries, england
3
animals, penguin
fruits, peach
drinks, tea
cities, glasgow
countries, scotland
4
animals, cow
fruits, mango
drinks, coke
cities, sydney
countries, australia
And, with eval, it would look like
Code:
for i in "${index[@]}" ; do echo ${i}; for j in "${all[@]}" ; do eval echo \$j, \${$j[\$i]}; done; done
0
animals, dog
fruits, orange
drinks, juice
cities, toronto
countries, canada
1
animals, cat
fruits, apple
drinks, milk
cities, paris
countries, france
2
animals, horse
fruits, grapes
drinks, coffee
cities, london
countries, england
3
animals, penguin
fruits, peach
drinks, tea
cities, glasgow
countries, scotland
4
animals, cow
fruits, mango
drinks, coke
cities, sydney
countries, australia
Yes that's what I want, with the correct grouping and all.
I am getting the expected output with 'eval' but not so with typeset:
Code:
abc@xyz$ ./loop.sh
./loop.sh: line 17: typeset: -n: invalid option
typeset: usage: typeset [-afFirtx] [-p] name[=value] ...
0
dog, animals
orange, fruits
juice, drinks
toronto, cities
canada, countries
1
dog,
orange,
juice,
toronto,
canada,
2
dog,
orange,
juice,
toronto,
canada,
3
dog,
orange,
juice,
toronto,
canada,
4
dog,
orange,
juice,
toronto,
canada,
abc@xyz$ bash --version
GNU bash, version 4.4.12(1)-release (x86_64-apple-darwin16.3.0)
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
I'm using side-loaded bash 4 on OS X courtesy of Homebrew, if it matters.
Also, I'm confused as to why the order is flipped.
Hi RudiC,
Thanks for letting me know bash now recognizes typeset -n. (It doesn't in the bash I have on macOS Sierra 10.12.6 which includes GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin16). And, apparently it doesn't with the bash on whatever OS Kingzy is using.)
Hi Kingzy,
It is always a good idea to tell us what operating system you're using (in addition to the shell). If we know what OS and shells you have available, we're less likely to offer suggestions that won't work in your environment. Assuming that you have access to a 1993 or later version of the Korn shell, the following should work...
I had hoped that with the example code I had provided, you would have been able to reconfigure the loops in my example to get whatever output was desired. For the output format requested in post #4, the following should suffice:
Code:
#!/bin/ksh
index=(0 1 2 3 4)
all=(animals fruits drinks cities countries)
animals=(dog cat horse penguin cow)
fruits=(orange apple grapes peach mango)
drinks=(juice milk coffee tea coke)
cities=(toronto paris london glasgow sydney)
countries=(canada france england scotland australia)
typeset -n arrayname
separator=
for subscript in "${!index[@]}"
do printf "$separator"
separator='\n'
for arrayname in "${all[@]}"
do printf '%s[%s]=%s\n' "${!arrayname}" "$subscript" "${arrayname[$subscript]}"
done
done
which just switches the inner and outer loops in the code I suggested before, changes the names of the arrays used as looping values, and adds code to add an empty line between groups. The above produces the output requested in post #4.
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