main.go

Documentation: github.com/jmespath/go-jmespath/cmd/jpgo

     1  /*Basic command line interface for debug and testing purposes.
     2  
     3  Examples:
     4  
     5  Only print the AST for the expression:
     6  
     7      jp.go -ast "foo.bar.baz"
     8  
     9  Evaluate the JMESPath expression against JSON data from a file:
    10  
    11      jp.go -input /tmp/data.json "foo.bar.baz"
    12  
    13  This program can also be used as an executable to the jp-compliance
    14  runner (github.com/jmespath/jmespath.test).
    15  
    16  */
    17  package main
    18  
    19  import (
    20  	"flag"
    21  	"fmt"
    22  	"io/ioutil"
    23  	"os"
    24  )
    25  
    26  import (
    27  	"encoding/json"
    28  
    29  	"github.com/jmespath/go-jmespath"
    30  )
    31  
    32  func errMsg(msg string, a ...interface{}) int {
    33  	fmt.Fprintf(os.Stderr, msg, a...)
    34  	fmt.Fprintln(os.Stderr)
    35  	return 1
    36  }
    37  
    38  func run() int {
    39  
    40  	astOnly := flag.Bool("ast", false, "Print the AST for the input expression and exit.")
    41  	inputFile := flag.String("input", "", "Filename containing JSON data to search. If not provided, data is read from stdin.")
    42  
    43  	flag.Parse()
    44  	args := flag.Args()
    45  	if len(args) != 1 {
    46  		fmt.Fprintf(os.Stderr, "Usage:\n\n")
    47  		flag.PrintDefaults()
    48  		return errMsg("\nError: expected a single argument (the JMESPath expression).")
    49  	}
    50  
    51  	expression := args[0]
    52  	parser := jmespath.NewParser()
    53  	parsed, err := parser.Parse(expression)
    54  	if err != nil {
    55  		if syntaxError, ok := err.(jmespath.SyntaxError); ok {
    56  			return errMsg("%s\n%s\n", syntaxError, syntaxError.HighlightLocation())
    57  		}
    58  		return errMsg("%s", err)
    59  	}
    60  	if *astOnly {
    61  		fmt.Println("")
    62  		fmt.Printf("%s\n", parsed)
    63  		return 0
    64  	}
    65  
    66  	var inputData []byte
    67  	if *inputFile != "" {
    68  		inputData, err = ioutil.ReadFile(*inputFile)
    69  		if err != nil {
    70  			return errMsg("Error loading file %s: %s", *inputFile, err)
    71  		}
    72  	} else {
    73  		// If an input data file is not provided then we read the
    74  		// data from stdin.
    75  		inputData, err = ioutil.ReadAll(os.Stdin)
    76  		if err != nil {
    77  			return errMsg("Error reading from stdin: %s", err)
    78  		}
    79  	}
    80  	var data interface{}
    81  	if err := json.Unmarshal(inputData, &data); err != nil {
    82  		return errMsg("Invalid input JSON: %s", err)
    83  	}
    84  	result, err := jmespath.Search(expression, data)
    85  	if err != nil {
    86  		return errMsg("Error executing expression: %s", err)
    87  	}
    88  	toJSON, err := json.MarshalIndent(result, "", "  ")
    89  	if err != nil {
    90  		return errMsg("Error serializing result to JSON: %s", err)
    91  	}
    92  	fmt.Println(string(toJSON))
    93  	return 0
    94  }
    95  
    96  func main() {
    97  	os.Exit(run())
    98  }
    99
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