Bash for loop skip first element of array

Question

In bash, I have a string, I want to convert in array and use it in a for loop but skipping the first element. The code below does not works:

build_string="100 99 98"
build_list=("$build_string")

echo $build_list
for i in "${build_list[@]:1}"
   do  echo "i: " $i
done

The for loop does not print anything. Could you help me? Thanks.

What does `echo $build_list` print? – Daemon Painter Aug 21 '19 at 06:47 — Daemon Painter, Aug 21 '19 at 06:47
Better, what does `declare -p build_list` output – David C. Rankin Aug 21 '19 at 06:53 — David C. Rankin, Aug 21 '19 at 06:53
It works using build_list=($build_string) – unrue Aug 21 '19 at 08:47 — unrue, Aug 21 '19 at 08:47

score 6 · Answer 1 · answered Aug 21 '19 at 06:52

I believe you are not converting the array properly (or at all). Please see this snippet:

build_string="100 99 98"
#build_list=("$build_string")  <-- this is not converting into array, following line is.
IFS=' ' read -r -a build_list <<< "$build_string"

echo $build_list
for i in "${build_list[@]:1}"
   do  echo "i: " $i
done

sleep 2

now the output is:

100
i:  99
i:  98

Which sounds reasonable. The 100 is printed when you ask echo $build_string. Reference: split string into array in bash

As pointed out by prefire, the double quotes on the second line are preventing array conversion. This snippet also works:

build_string="100 99 98"
build_list=($build_string)

echo $build_list
for i in "${build_list[@]:1}"
   do  echo "i: " $i
done

sleep 2

Note: I've added a sleep 2 at the end, so I can see what is being printed.

score 3 · Answer 2 · answered Aug 21 '19 at 06:48

3

Replace the second line with this:

build_list=($build_string)

answered Aug 21 '19 at 06:48

prefire

66
2

score 1 · Answer 3 · edited Aug 21 '19 at 10:27

1

build_list=("$build_string")

build_list array only have one item, so ${build_list[@]:1 is empty.

edited Aug 21 '19 at 10:27

Shaheryar.Akram

722
10
19

answered Aug 21 '19 at 10:01

黄轩辕

11
2

Bash for loop skip first element of array

3 Answers3