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, feature-complete and tested against "the one true AWK" test suite.
Read more about how GoAWK works and performs here.
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
On Windows, " is the shell quoting character, so use " around the entire AWK program on the command line, and use ' around AWK strings -- this is a non-POSIX extension to make GoAWK easier to use on Windows:
C:\> goawk "BEGIN { print 'foo', 42 }"
foo 42
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.ExecProgram() to control execution, set variables, etc:
src := "{ print NR, tolower($0) }"
input := "A\naB\nAbC"
prog, err := parser.ParseProgram([]byte(src), nil)
if err != nil {
fmt.Println(err)
return
}
config := &interp.Config{
Stdin: bytes.NewReader([]byte(input)),
Vars: []string{"OFS", ":"},
}
_, err = interp.ExecProgram(prog, config)
if err != nil {
fmt.Println(err)
return
}
// Output:
// 1:a
// 2:ab
// 3:abc
Read the GoDoc documentation for more details.
Differences from AWK
The intention is for GoAWK to conform to awk's behavior and 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! You can even call custom Go functions from your AWK scripts.
- I/O-bound AWK scripts (which is most of them) are significantly faster than
awk, and on a par withgawkandmawk. - The parser supports
'single-quoted strings'in addition to"double-quoted strings", primarily to make Windows one-liners easier (the Windowscmd.exeshell uses"as the quote character).
Things AWK has over GoAWK:
- CPU-bound AWK scripts are slightly slower than
awk, and about twice as slow asgawkandmawk. - AWK is written by Brian Kernighan.
Stability
This project has a good suite of tests, and I've used it a bunch personally, but it's certainly not battle-tested or heavily used, so please use at your own risk. I intend not to change the Go API in a breaking way.
License
GoAWK is licensed under an open source MIT license.
The end
Have fun, and please contact me if you're using GoAWK or have any feedback!