How to convert my array to a string in Bash?

Question

This is my Bash script that reads values from a temperature sensor and shows them in a line. I want to separate my array elements by a comma, like this example: [1,2,3,5], then to replace a line that exists in another file by this string.

temp.sh:

#!/bin/bash
for ((i=0 ; 12 - $i ; i++))
  do
  x=$(cat /sys/bus/w1/devices/28-0000075292ed/w1_slave | grep "t=" | awk -F "t=" '{print $2/1000}')
  field[$i]=$x
  echo "${field[$i]}"
done | column

Is column doing anything here? Does the echo output more than one value on a given line? What does the output of this command look like exactly? What about if you don't use column? — Etan Reisner
– Etan Reisner, Commented Mar 30, 2016 at 22:40
Why are you sampling the same device each time through the loop? — Etan Reisner
– Etan Reisner, Commented Mar 30, 2016 at 22:41
@EtanReisner I'm assuming to get temperatures multiple times and average the value or something similar. Although many of these sensors don't like being read over and over without sleeping inbetween. — Will
– Will, Commented Mar 30, 2016 at 22:45
Are you saying you want the values of field as a string? You can always do mystr="${field[@]}" for a space separated string of values. If you want to remove the spaces, then tr -d ' ' <<<$mystr. — David C. Rankin
– David C. Rankin, Commented Mar 30, 2016 at 23:00
@Etan Reisner column gives me the opportunity to have the array elements horizontally I am sampling the same device to see the change of temperature and show them in graph ( the file that I said I want to access is a html file that contains the graph) — user5996908
– user5996908, Commented Mar 31, 2016 at 11:02

Community · Accepted Answer · 2017-04-13 12:36:24Z

5

So one way we could do this is to emulate the join() functionality provided by many languages:

function join()
{
    local IFS="$1"
    shift
    echo "$*"
}

Then we can call:

READINGS="[$(join "," "${field[@]})"]"

Here's an example:

$ MY_ARRAY=("one" "two" "three")
$ join "," "${MY_ARRAY[@]}"
one,two,three

This works by changing Bash's Internal Field Separator. $* is the used for expanding all arguments using the $IFS as a separator.

We could also avoid the join function and just do it like this:

READINGS="[$(IFS=","; echo "${field[*]}")]"

edited Apr 13, 2017 at 12:36

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answered Mar 30, 2016 at 22:44

Will

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2 Comments

user5996908 Over a year ago

when I tried it , it shows the same result as without IFS : pi@raspberrypi:~ $ ./temp.sh 21.437 21.437 21.437 21.437 21.437 21.437 21.437 21.437 21.5 21.5 21.5 21.5

Will Over a year ago

If not, try posting your new code in an edit to the question and I'll take a look.

user5996908 · Accepted Answer · 2016-04-02 10:39:49Z

1

Thank you I have found a solution

#!/bin/bash
f="myArray_a = ["
for ((i=0 ; 12 - $i ; i++))
  do
  x=$(cat /sys/bus/w1/devices/28-0000075292ed/w1_slave | grep "t=" | awk - F "t=" '{print $2/1000}')
  if [ $i -eq 11 ]
  then
  x=$(printf %.3f] $x)
  f="$f $x"
  echo "$f"
  else
  x=$(printf %.3f, $x)
  f="$f $x"
  fi



done | column

answered Apr 2, 2016 at 10:39

user5996908

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