bash awk split string into array

Question

I am using awk to split a string into array using a specific delimiter. Now, I want to perform some operation on each element of the array.

I am able to extract a single element like this:

#! /bin/bash

b=12:34:56
a=`echo $b | awk '{split($0,numbers,":"); print numbers[1]}'`
echo $a

I want to do something like this:

#! /bin/bash

b=12:34:56
`echo $b | awk '{split($0,numbers,":");}'`
for(i=0;i<length(numbers);i++)
{
   // perform some operation using numbers[i]
}

how would I do something like this in bash scripting?

as said below you really don't need awk here but if you want to use "back in the shell" a result produced by awk you'll have to output it from within awk ; for example numbers=$(echo...|awk '{split(...);print numbers}'); for n in $numbers; do ... done (which is simpler than using indices but you can also do numbers=($(...)); for((i=0; i<${#numbers};++i)); do echo ${numbers[i]} ; done. HTH — Max
– Max, Commented Jul 17, 2020 at 17:33

Graham Perks · Accepted Answer · 2016-04-06 02:32:48Z

20

None of these answers used awk (weird). With awk you can do something like:

echo 12:34:56 | awk '{split($0,numbers,":")} END {for(n in numbers){ print numbers[n] }}'

replacing print numbers[n] with whatever it is you want to do.

edited Apr 6, 2016 at 2:32

Graham Perks

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answered Nov 20, 2015 at 15:01

user153275

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3 Comments

chepner Over a year ago

They don't use awk because there's no reason to start an external program to do something bash can already do.

user153275 Over a year ago

But if the question is "how to do this in awk" and none of the answers involve awk, the question isn't really answered. The result is that Google searches return a useless result for anyone trying to figure out how to do exactly this in awk (which may be useful because they're doing other things in awk already and just want to add this one thing).

Nick Over a year ago

I indeed came to this question looking for exactly and specifically how to do it in awk. So this answer was the only answer for me.

Mat · Accepted Answer · 2013-10-26 12:50:02Z

17

You don't really need awk for that, bash can do some string processing all by itself.

Try:

b=12:34:56
for element in ${b//:/ } ; do
  echo $element
done

If you need a counter, it's pretty trivial to add that.

See How do I do string manipulations in bash? for more info on what you can do directly in bash.

answered Oct 26, 2013 at 12:50

Mat

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Comments

ensc · Accepted Answer · 2013-10-26 13:02:21Z

6

b=12:34:56
IFS=:
set -- $b
for i; do echo $i; done

This does not contain bashisms but works with every sh.

answered Oct 26, 2013 at 13:02

ensc

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2 Comments

chepner Over a year ago

Be aware that this overwrites the positional arguments in $@, so you'll need to save them as necessary before running the set command.

ensc Over a year ago

of course; usually, I put complex tasks in functions which have their own $@ context (saving "$@" is too ugly and nearly impossible without bashisms).

chepner · Accepted Answer · 2013-10-26 13:46:04Z

2

The bash read command can split a string into an array by itself:

IFS=: read -a numbers <<< "$b"

To see that it worked:

echo "Hours: ${numbers[0]}"
echo "Minutes: ${numbers[1]}"
echo "Seconds: ${numbers[2]}"

for val in "${numbers[@]}"; do
   seconds=$(( seconds * 60 + $val ))
done

answered Oct 26, 2013 at 13:46

chepner

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Comments

markeissler · Accepted Answer · 2014-11-03 22:53:36Z

1

Another neat way, not using awk, but build-in 'declare':

b=12:34:56

# USE IFS for splitting (and elements can have spaces in them)
IFS=":"
declare -a elements=( $b )
#show contents
for (( i=0 ; i < ${#elements[@]}; i++ )); do
    echo "$i= ${elements[$i]}"
done

edited Nov 3, 2014 at 22:53

markeissler

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answered Dec 1, 2013 at 10:21

vkersten

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1 Comment

chepner Over a year ago

This doesn't work in all cases; leaving b unquoted leaves it subject to pathname expansion as well as word-splitting.

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