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sedavidw
sedavidw

Reputation: 11691

Iterate over json array of dates in bash (has whitespace)

I have an array that is being stored in a bash variable that is a json array of dates (it's currently being produced by a separate script). It looks like the following

["2019-09-19 03:13:29", "2019-09-19 20:20:18", "2019-09-19 18:19:50", "2019-09-19 06:07:17", "2019-09-19 11:53:25"]

I want to iterate over these dates and preserve the white space in the dates so I can use them with the gdate command. I'm currently using jq but that is splitting up the date part from the time part. i.e.

dates=$(python date_producing_script.py | jq -c -r '.[]')
for date in ${dates[@]}; do
    echo $date
    #end goal is to do something here w/ gdate ex gdate -d $date ...
done

However this gives something like

2019-09-19
03:13:29
2019-09-19
20:20:18
2019-09-19
18:19:50
2019-09-19
06:07:17
2019-09-19
11:53:25

Where I'm looking for something like the following

2019-09-19 03:13:29
2019-09-19 20:20:18
2019-09-19 18:19:50
2019-09-19 06:07:17
2019-09-19 11:53:25

(one confusing thing for me here is that if I just do the python date_producing_script.py | jq -c -r '.[]' command in a terminal it looks the way I want it to)

However ideally I would want something like. Is there anyway to get this result from the input in shell script

Upvotes: 1

Views: 2870

Answers (3)

EchoMike444
EchoMike444

Reputation: 1692

One of your issue is when you populate dates array , and the other is when you want to use the array for loop .

My proposal is :

  • change jq to generate a long string of date with = as a separator
  • tell bash to use = as separator instead of <space><tab><line return>
  • you must use the syntax "$dates[@]" instead of $dates[@]

Your script will be like : 

OLDIFS=$IFS ;
IFS="=" ;
dates=( python date_producing_script.py | jq  -c -j -r '.[]|(.,"=")') );
IFS=$OLDIFS

for d in "${dates[@]}" ;
do 
    echo $d ;
done

Upvotes: 0

peak
peak

Reputation: 116770

Your jq is fine; the problem is in the way you're looping through the bash array, as can be seen from this bash typescript:

$ ary=("a b" "c d")
$ for x in ${ary[@]} ; do echo "$x" ; done
a
b
c
d
$ for x in "${ary[@]}" ; do echo "$x" ; done
a b
c d
$

IOW

"${dates[@]}"

Upvotes: 4

Nic3500
Nic3500

Reputation: 8611

Here is one solution:

#!/bin/bash
#
IFS=','
dates='["2019-09-19 03:13:29", "2019-09-19 20:20:18", "2019-09-19 18:19:50", "2019-09-19 06:07:17", "2019-09-19 11:53:25"]'

for date in ${dates[@]}
do
    # Cleanup $date
    thedate=$(echo $date | tr -d '\[\]"' | sed -e 's/^[[:space:]]*//')
    echo "-->$thedate<--"
done
  • IFS: sets the separator as ,
  • $dates is now separated on ,
  • $thedate is $date with [, ], " removed. The sed is to remove prefix spaces.
  • I put --> and <-- to show that $thedate does not include any spaces.

There are most probably solutions with awk too.

Upvotes: 0

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