BASH - Convert array to list

Question

i need convert an array to list and wrtiting in a file, but the result is without space or delimiter, eg:

 declare -a INSTANCEID=`ec2-run-instances --instance-count 2 --key xxx --instance-type t2.micro [...] ${AMIID} | ./getInstanceId.pl -`

if i make an echo of INSTANCEID i have i-75bxxxfai-72bxxxfd. How can separate the two values (i-75bxxxfa and i-72bxxxfd) and writing in a file, one per lines?

I have tried with:

printf "%s\n"  "${INSTANCEID[@]}" > file.txt

but i have always the same output

The command launch two distinct instance, then i think is an array — stecog
– stecog, Commented Sep 21, 2016 at 9:39
@hellboy: I think you may want to re-check that, if they are distinct values, printf "%s\n" "${INSTANCEID[@]}" would have already printed them on separate lines. — Inian
– Inian, Commented Sep 21, 2016 at 9:41
echo 'i-75bxxxfai-72bxxxfd' |awk -v FS="-" -v OFS="\n" '{split($2,a,"i");print "$1" FS a[1], "$1" FS $3}' — P....
– P...., Commented Sep 21, 2016 at 9:51
Thanks but is no correct, every instance start with i- and can finish with i. I need to use also a for because the instance they can be more than 2 — stecog
– stecog, Commented Sep 21, 2016 at 9:58
Now, seems a string instead array, then i need separate the id's in a list, the id's starts with i- and can finish with i, can be more than two and can be long more characters — stecog
– stecog, Commented Sep 21, 2016 at 10:08

Inian · Accepted Answer · 2016-09-21 12:59:42Z

1

As per the comments over in the question description, OP wants to strip a string carrying instances.

A portable bash logic for this would be something like below. The below statements can be just run in command line.

$ INSTANCEID=i-75bxxxfai-72bxxxfd
$ IFS="-" read -ra instances <<<"$INSTANCEID"

$ for (( i=1; i<=$(( ${#instances[*]} -1 )); i++ )); \
    do printf "%s\n" "${instances[0]}-${instances[$i]//i} "; done

This will print the individual instances as

i-75bxxxfa
i-72bxxxfd

The idea here is

Split the input string from $INSTANCEID variable with de-limiter as - and read them into an array(read command with -a for array-read operation). The array contains entries as i, 75bxxxfai, 72bxxxfd
Now looping over the array instances over the total count "${#instances[*]}" - 1 and forming the string as "${instances[$0]}-${instances[$i]//i}" which is the string i followed by de-limiter - and the subsequent elements of the array with i removed ("${instances[$i]//i}")

You can see it working for any number of strings with multiple instance id's as:-

With 3 instances

$ INSTANCEID=i-75bxxxfai-72bxxxfdi-72bxxxfdi
$ IFS="-" read -ra instances <<<"$INSTANCEID"

$ for (( i=1; i<=$(( ${#instances[*]} -1 )); i++ )); \
    do printf "%s\n" "${instances[0]}-${instances[$i]//i} "; done

i-75bxxxfa
i-72bxxxfd
i-72bxxxfd

With 4 instances

$ INSTANCEID=i-75bxxxfai-72bxxxfdi-72bxxxfdii-7894xxuk
$ IFS="-" read -ra instances <<<"$INSTANCEID"

$ for (( i=1; i<=$(( ${#instances[*]} -1 )); i++ )); \
    do printf "%s\n" "${instances[0]}-${instances[$i]//i} "; done

i-75bxxxfa
i-72bxxxfd
i-72bxxxfd
i-7894xxuk

Read more about bash- Shell Parameter Expansion

edited Sep 21, 2016 at 12:59

answered Sep 21, 2016 at 11:23

Inian

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4 Comments

stecog Over a year ago

I have an error "Syntax error, expected token in line do printf "%s\n" "${instances[$0]}-${instances[$i]//i} "; done

Inian Over a year ago

@hellb0y77: Run it in a single line. for (( i=1; i<=("${#instances[*]}" - 1); i++ )); do printf "%s\n" "${instances[$0]}-${instances[$i]//i} "; done without any breaks, I added a line break for more readability

Inian Over a year ago

Working fine on my shell, GNU bash 4.1.2; Which version are you on ?

gniourf_gniourf Over a year ago

A more idiomatic loop: for inst in "${instances[@]:1}"; do printf '%s-%s\n' "${instances[0]}" "${inst//i}"; done.

peladux · Accepted Answer · 2024-12-20 23:20:32Z

0

set -- ${INSTANCEID[*]}

echo $@

answered Dec 20, 2024 at 23:20

peladux

1

1 Comment

Mario Mateaș Dec 25, 2024 at 4:28

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