GoAWK: an AWK interpreter written in Go

AWK is a fascinating text-processing language, and somehow after reading the delightfully-terse The AWK Programming Language I was inspired to write an interpreter for it in Go. So here it is, pretty much feature-complete and tested against "the one true AWK" test suite.

Basic usage

To use the command-line version, simply use go get to install it, and then run it using goawk (assuming $GOPATH/bin is in your PATH):

$ go get github.com/benhoyt/goawk
$ goawk 'BEGIN { print "foo", 42 }'
foo 42
$ echo 1 2 3 | goawk '{ print $1 + $3 }'
4

To use it in your Go programs, you can call interp.Exec() directly for simple needs:

input := bytes.NewReader([]byte("foo bar\n\nbaz buz"))
err := interp.Exec("$0 { print $1 }", " ", input, nil)
if err != nil {
    fmt.Println(err)
    return
}
// Output:
// foo
// baz

Or you can use the parser module and then interp.New() and Interp.Exec() to control execution, set variables, etc:

src := "{ print $1+$2 }"
input := "1,2\n3,4\n5,6"

prog, err := parser.ParseProgram([]byte(src))
if err != nil {
    fmt.Println(err)
    return
}
p := interp.New(nil, nil)
p.SetVar("FS", ",")
err = p.Exec(prog, bytes.NewReader([]byte(input)), nil)
if err != nil {
    fmt.Println(err)
    return
}
// Output:
// 3
// 7
// 11

Read the GoDoc documentation for more details.

Differences from AWK

The intention is for GoAWK to conform to the POSIX AWK spec, but this section describes some areas where it's different.

Additional features GoAWK has over AWK:

• It's embeddable in your Go programs. :-)
• I/O-bound AWK scripts (i.e., most of them) are significantly faster than awk, and on a par with gawk.
• The parser supports 'single-quoted strings' in addition to "double-quoted strings", primarily to make Windows one-liners easier (the Windows cmd.exe shell uses " as the quote character).

Things AWK has over GoAWK:

• CPU-bound AWK scripts are slightly slower than awk, and about twice as slow as gawk.
• GoAWK has a couple of known syntax quirks, but most real code shouldn't run into them (commented-out tests in interp/interp_test.go). I intend to fix these soon.

Stability

This is a beta, pre-1.0 version of GoAWK. It's working quite well and is fairly thoroughly tested, but I'm free to change the exported API if it makes sense. It shouldn't change too much, but there may be small changes in the signature of a few functions. I intend to publish a v1.0 with a stable API around October 2018.

The end

Have fun, and please contact me if you're using GoAWK or have any feedback!