poorjson.sh

A minimal POSIX compatible JSON parser and query tool written in pure 60 lines of POSIX Shell code. The goal is to be POSIX compatible, lightweight, and fast. Only requires sed.

Usage:

# Just pipe JSON to it, and use parameters to query:
# (Note strings are quoted with "")
echo '{"key": ["ele1", "ele2", "ele3", "ele4"]}' | ./poorjson.sh '"key"' 2
# Prints:
"ele3"

# If output is array or object, it's printed a token per line
echo '{"top-key": {"key1": [ "value1", "value2"],  "key2": "value2"} }' | ./poorjson.sh '"top-key"' '"key1"'
# Prints:
[
"value1"
,
"value2"
]

# Use \* to match anything, multilevel matching is supported:
echo '{"key0": {"key1": ["ele1-1", "ele1-2"], "key2": ["ele2-1", "ele2-2"]}}' | ./poorjson.sh '"key0"' \* 1
# Prints:
"ele1-1"
"ele2-1"

# poorjson.sh prints the whole JSON one token per line if no param is given:
echo '{"key0": [{"key1": "val1"}]}' | ./poorjson.sh
# Prints:
{
"key0"
:
[
{
"key1"
:
"val1"
}
]
}

# poorjson.sh prints basic error message for invalid JSON
# To simply check if a JSON string is valid:
echo '{"key": "val"}' | ./poorjson.sh - && echo "valid" || echo "invalid"
# Prints:
valid

echo '{"key":: "val"}' | ./poorjson.sh - && echo "valid" || echo "invalid"
# Prints:
Unexpected token: ":"
invalid

echo '' | ./poorjson.sh - && echo "valid" || echo "invalid"
# Prints:
Unexpected EOF after: ""
invalid

Known issues

• If the same key appears multiple times in an object, poorjson.sh will simply parse them repeatedly.
• Due to the function call depths limit in Shell, JSON with thousands of levels of embedment can't be processed by poorjson.sh. But except that, it should be good enough for most common usage.

Test and comparison

Test result with JSONTestSuite: