How do I split a string against a character in BASH?

Question

I would like to be able to split an authorization code by the - character so that I can operate on each segment individually. I do not want to use external binaries (awk, grep) - this is to be as minimalistic as possible. What are some ways I can achieve this?

Here is an example auth code:

82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb

Normally you would use cut. Why the limitation on external binaries though? — Grant, Aug 22 '12 at 17:35
This is on an embedded Linux device with limited access to them. — Jay Hellwig, Aug 22 '12 at 17:38

Daniel Li · Accepted Answer · 2012-09-17T19:17:40.393

15

Try using the Internal Field Separator (IFS):

AUTH_CODE='82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb'

OIFS=$IFS                   # store old IFS in buffer
IFS='-'                     # set IFS to '-'

for i in ${AUTH_CODE[@]}    # traverse through elements
do
  echo $i
done

IFS=$OIFS                   # reset IFS to default (whitespace)

Output:

82a8
bd7d
986d
9dc9
41f5
fc02
2c20
3175
097a
c1eb

By setting the Internal Field Separator, you split AUTH_CODE on the - character, allowing you to traverse through the newly-created elements in a foreach loop.

edited Sep 17 '12 at 19:17

answered Aug 22 '12 at 17:35

Daniel Li

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If you haven't altered IFS from its default, you can ignore the saving the value of IFS into OIFS parts and just `unset IFS` when you're done. – violet Sep 12 '12 at 02:26
Could you explain the syntax `${AUTH_CODE[@]}`? Is the `[@]` what causes bash to split the string? – Sam Goldberg Dec 16 '14 at 21:35
I tested this on Linux, it seems like was only required to set the IFS, and after that, the string is already split. ie: ` OIFS=$IFS;IFS='-';for s in $AUTH;do echo $s;done;IFS=$OIFS` The `[@]` did not seem to be needed at all? – Sam Goldberg Dec 16 '14 at 21:45

Tometzky · Answer 2 · 2012-09-17T08:24:23.147

5

You can use IFS but this is simpler:

echo "82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb"- \
  | while read -d - i; do echo "$i"; done

Please take notice of added - after string to split — read will ignore the last token otherwise.

edited Sep 17 '12 at 08:24

answered Aug 22 '12 at 17:47

Tometzky

2,649
4
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32

1

this doesn't add the readability I want though, considering the operations on each element is rather intensive – Jay Hellwig Aug 22 '12 at 17:50
2

I don't understand. What's not readable? You don't need to do this in one line — you can have as many lines as you want between `do` and `done`. – Tometzky Aug 22 '12 at 17:54

score 4 · Answer 3 · edited Aug 29 '12 at 14:11

4

Another way with pattern matching and array:

AUTH_CODE='82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb'
array=( ${AUTH_CODE//-/ } )
for j in ${array[@]} ; do echo $j ; done

edited Aug 29 '12 at 14:11

adaptr

16,479
21
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answered Aug 23 '12 at 13:50

ott--

1,081
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score 2 · Answer 4 · answered Aug 29 '12 at 14:57

2

Just use parameters expansion:

AUTH_CODE='82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb'
echo "${AUTH_CODE//-/$'\n'}"

Output:

82a8
bd7d
986d
9dc9
41f5
fc02
2c20
3175
097a
c1eb

answered Aug 29 '12 at 14:57

Thor

465
5
14

score 0 · Answer 5 · answered Aug 23 '12 at 14:02

0

for i in {1..10}; do echo '82a8-bd7d-986d-9dc9-41f5-fc02-2c20-3175-097a-c1eb'|cut -d"-" -f$i;done

answered Aug 23 '12 at 14:02

Tom

146
1

You might have missed the part about "no external binaries". – nickgrim Sep 17 '12 at 08:48

How do I split a string against a character in BASH?

5 Answers5