jawk

awk for JSON.

Install

Run make install as root to install jawk to /usr/local/bin.

or

Copy the jawk file to somewhere in your PATH.

Examples

$ echo '{"age":10}' | jawk '{print _["age"]}'
10

$ echo '{"person":{"name":"Jason"}}' | jawk '{print _["person","name"]}'
Jason

$ echo '[4,2,0]' | jawk '{while (++i <= _["length"]) print _[i]}'
4
2
0

$ echo '[{"x":6},{"x":7}]' | jawk '{while (++i <= _["length"]) print _[i,"x"]}'
6
7

$ printf '{"x":6}\n{"x":7}\n' | jawk '{print _["x"]}'
6
7

$ echo '{"name":{"first":"Jason"},"age":25}' | jawk '{
	keys(o); for (k in o) print k, _[o[k],JSON]
}'
name {"first":"Jason"}
age 25

$ echo '{"name":"Jason"}' | jawk '{print _["name",JSON]}'
"Jason"

# Try it with real data!
curl -Ls https://api.github.com/repos/onetrueawk/awk |
jawk '{print "id:", _["id"], "owner.id:", _["owner","id"]}'

curl -Ls https://api.github.com/repos/onetrueawk/awk/commits |
jawk '{
	while (++i <= _["length"]) {
		sha = _[i,"sha"]
		message = _[i,"commit","message"]
		l = index(message, "\n")
		print sha, substr(message, 1, l ? l - 1 : 50)
	}
}'

curl -Ls https://api.github.com/repos/onetrueawk/awk/commits |
jawk '{while (++i <= _["length"]) printf("{\"sha\":%s}\n",_[i,"sha",JSON])}'

Details

jawk makes available each JSON object using the _ variable. jawk programs are awk programs, and all awk features and functions are available. Nested fields can be accessed using standard awk indexing (eg. _["foo","bar"]). Some conversions are done: the value true is converted to 1, false is converted to 0 and null is converted to "". Arrays are 1-indexed.

Properties

_[p]

Return the value of the object at path p if it's a primitive, or p if it's an object or array. If the root object is a primitive, _[0] returns its value.

_[[p,]"length"]

Return the length of the array at path p, or the root array if p is omitted.

_[[p,]JSON]

Return the JSON form of the object at path p, or the root object if p is omitted.

_[[p,]TYPE]

Return the type of the object at path p, or the root object if p is omitted. The result will be one of boolean, null, array, object, string or number.

Functions

keys(a[, o])

Populate the array a with the keys of the object at path o such that a[k] = p where k is the key and p is its full path. The path can then be passed to _ to retrieve its value. If o isn't provided, a is populated with the keys and paths of the root object. Returns the number of keys.

Development

Make changes to src/jawk.sh and run make to produce jawk. Run make -B test to test changes.