Command-line tool for converting PLIST to JSON?

If you are on a Mac you can use the plutil tool on the command line (this comes with the developer tools I believe):

plutil -convert json Data.plist

as mentioned in the comments, this will overwrite the existing data. To output to a new file

plutil -convert json -o Data.json Data.plist

The following gets the job done—

// convertPlistToJSON.m
#import <Foundation/Foundation.h>
#import "JSONKit.h"

int main(int argc, char *argv[]) {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

  if(argc != 3) { fprintf(stderr, "usage: %s FILE_PLIST FILE_JSON\n", argv[0]); exit(5); }

  NSString *plistFileNameString = [NSString stringWithUTF8String:argv[1]];
  NSString *jsonFileNameString  = [NSString stringWithUTF8String:argv[2]];

  NSError *error = NULL;

  NSData *plistFileData = [NSData dataWithContentsOfFile:plistFileNameString options:0UL error:&error];
  if(plistFileData == NULL) {
    NSLog(@"Unable to read plist file.  Error: %@, info: %@", error, [error userInfo]);
    exit(1);
  }

  id plist = [NSPropertyListSerialization propertyListWithData:plistFileData options:NSPropertyListImmutable format:NULL error:&error];
  if(plist == NULL) {
    NSLog(@"Unable to deserialize property list.  Error: %@, info: %@", error, [error userInfo]);
    exit(1);
  }

  NSData *jsonData = [plist JSONDataWithOptions:JKSerializeOptionPretty error:&error];
  if(jsonData == NULL) {
    NSLog(@"Unable to serialize plist to JSON.  Error: %@, info: %@", error, [error userInfo]);
    exit(1);
  }

  if([jsonData writeToFile:jsonFileNameString options:NSDataWritingAtomic error:&error] == NO) {
    NSLog(@"Unable to write JSON to file.  Error: %@, info: %@", error, [error userInfo]);
    exit(1);
  }

  [pool release]; pool = NULL;
  return(0);
}

It does some reasonable error checking, but it's not bullet proof. Use at your own risk.

You'll need JSONKit to build the tool. Place JSONKit.m and JSONKit.h in the same directory as convertPlistToJSON.m, and then compile with:

shell% gcc -o convertPlistToJSON convertPlistToJSON.m JSONKit.m -framework Foundation

Usage:

shell% convertPlistTOJSON
usage: convertPlistToJSON FILE_PLIST FILE_JSON

shell% convertPlistTOJSON input.plist output.json

Reads in input.plist, and writes the pretty printed JSON to output.json.