If you really cannot use a proper JSON parser such as jq[1]
, try an awk-based solution:
Bash 4.x:
readarray -t values < <(awk -F\" 'NF>=3 {print $4}' myfile.json)
Bash 3.x:
IFS=$'\n' read -d '' -ra values < <(awk -F\" 'NF>=3 {print $4}' myfile.json)
This stores all property values in Bash array ${values[@]}, which you can inspect with
declare -p values.
These solutions have limitations:
- each property must be on its own line,
- all values must be double-quoted,
- embedded escaped double quotes are not supported.
All these limitations reinforce the recommendation to use a proper JSON parser.
Note: The following alternative solutions use the Bash 4.x+ readarray -t values command, but they also work with the Bash 3.x alternative, IFS=$'\n' read -d '' -ra values.
grep + cut combination: A single grep command won’t do (unless you use GNU grep – see below), but adding cut helps:
readarray -t values < <(grep '"' myfile.json | cut -d '"' -f4)
GNU grep: Using -P to support PCREs, which support \K to drop everything matched so far (a more flexible alternative to a look-behind assertion) as well as look-ahead assertions ((?=...)):
readarray -t values < <(grep -Po ':\s*"\K.+(?="\s*,?\s*$)' myfile.json)
Finally, here’s a pure Bash (3.x+) solution:
What makes this a viable alternative in terms of performance is that no external utilities are called in each loop iteration; however, for larger input files, a solution based on external utilities will be much faster.
#!/usr/bin/env bash
declare -a values # declare the array
# Read each line and use regex parsing (with Bash's `=~` operator)
# to extract the value.
while read -r line; do
# Extract the value from between the double quotes
# and add it to the array.
[[ $line =~ :[[:blank:]]+\"(.*)\" ]] && values+=( "${BASH_REMATCH[1]}" )
done < myfile.json
declare -p values # print the array
[1] Here’s what a robust jq-based solution would look like (Bash 4.x):
readarray -t values < <(jq -r '.[]' myfile.json)