Prerequisite
For all of the below, it's assumed that your content is in a shell variable named s:
s='CONTAINER|CPU%|MEMUSAGE/LIMIT|MEM%|NETI/O|BLOCKI/O|PIDS
nginx_container|0.02%|25.09MiB/15.26GiB|0.16%|0B/0B|22.09MB/4.096kB|0'
What (modern jq)
# thanks to @JeffMercado and @chepner for refinements, see comments
jq -Rn '
( input | split("|") ) as $keys |
( inputs | split("|") ) as $vals |
[[$keys, $vals] | transpose[] | {key:.[0],value:.[1]}] | from_entries
' <<<"$s"
How (modern jq)
This requires very new (probably 1.5?) jq to work, and is a dense chunk of code. To break it down:
- Using
-n prevents jq from reading stdin on its own, leaving the entirety of the input stream available to be read by input and inputs -- the former to read a single line, and the latter to read all remaining lines. (-R, for raw input, causes textual lines rather than JSON objects to be read).
- With
[$keys, $vals] | transpose[], we're generating [key, value] pairs (in Python terms, zipping the two lists).
- With
{key:.[0],value:.[1]}, we're making each [key, value] pair into an object of the form {"key": key, "value": value}
- With
from_entries, we're combining those pairs into objects containing those keys and values.
What (shell-assisted)
This will work with a significantly older jq than the above, and is an easily adopted approach for scenarios where a native-jq solution can be harder to wrangle:
{
IFS='|' read -r -a keys # read first line into an array of strings
## read each subsequent line into an array named "values"
while IFS='|' read -r -a values; do
# setup: positional arguments to pass in literal variables, query with code
jq_args=( )
jq_query='.'
# copy values into the arguments, reference them from the generated code
for idx in "${!values[@]}"; do
[[ ${keys[$idx]} ]] || continue # skip values with no corresponding key
jq_args+=( --arg "key$idx" "${keys[$idx]}" )
jq_args+=( --arg "value$idx" "${values[$idx]}" )
jq_query+=" | .[\$key${idx}]=\$value${idx}"
done
# run the generated command
jq "${jq_args[@]}" "$jq_query" <<<'{}'
done
} <<<"$s"
How (shell-assisted)
The invoked jq command from the above is similar to:
jq --arg key0 'CONTAINER' \
--arg value0 'nginx_container' \
--arg key1 'CPU%' \
--arg value1 '0.0.2%' \
--arg key2 'MEMUSAGE/LIMIT' \
--arg value2 '25.09MiB/15.26GiB' \
'. | .[$key0]=$value0 | .[$key1]=$value1 | .[$key2]=$value2' \
<<<'{}'
...passing each key and value out-of-band (such that it's treated as a literal string rather than parsed as JSON), then referring to them individually.
Result
Either of the above will emit:
{
"CONTAINER": "nginx_container",
"CPU%": "0.02%",
"MEMUSAGE/LIMIT": "25.09MiB/15.26GiB",
"MEM%": "0.16%",
"NETI/O": "0B/0B",
"BLOCKI/O": "22.09MB/4.096kB",
"PIDS": "0"
}
Why
In short: Because it's guaranteed to generate valid JSON as output.
Consider the following as an example that would break more naive approaches:
s='key ending in a backslash\
value "with quotes"'
Sure, these are unexpected scenarios, but jq knows how to deal with them:
{
"key ending in a backslash\\": "value \"with quotes\""
}
...whereas an implementation that didn't understand JSON strings could easily end up emitting:
{
"key ending in a backslash\": "value "with quotes""
}
