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main.go
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main.go
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package main
import (
"bytes"
log "github.com/Sirupsen/logrus"
"os"
)
/*
A command-line driver for evaluating DPath expressions.
*/
func main() {
var parseTreeBuf bytes.Buffer
var r bool
if len(os.Args) < 2 {
log.Fatal("Must provide a DPath expression.")
}
// Parse the DPath expression.
tree, err := ParseString(os.Args[1])
if err != nil {
log.WithFields(log.Fields{
"error": err,
}).Fatal("Syntax error.")
}
// Log the parse tree.
parseTreeBuf.WriteString("Parse Tree:\n")
tree.Print(&parseTreeBuf, 0)
log.WithFields(log.Fields{
"tree": parseTreeBuf.String(),
}).Debug("Created parse tree.")
// Evaluate the expression and print the results.
ctx := DefaultContext()
seq, err := tree.Evaluate(ctx)
if err != nil {
log.WithFields(log.Fields{
"error": err,
}).Fatal("Error while evaluating expression.")
}
for r, err = seq.Next(ctx); r && err == nil; r, err = seq.Next(ctx) {
err = seq.Value().Print(os.Stdout)
}
if err != nil {
log.WithFields(log.Fields{
"error": err,
}).Fatal("Error while iterating.")
}
}
func init() {
// Log as JSON instead of the default ASCII formatter.
log.SetFormatter(&log.TextFormatter{})
// Output to stderr instead of stdout, could also be a file.
log.SetOutput(os.Stderr)
// Only log the warning severity or above.
log.SetLevel(log.ErrorLevel)
}