json_extract.c

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#include <options/options.h>
#include "../csm/csm_all.h"
 
int main(int argc, const char * argv[]) {
        sm_set_program_name(argv[0]);
        
        int nth;
        const char*input_filename;
        const char*output_filename;
        
        struct option* ops = options_allocate(3);
        options_int(ops, "nth", &nth, 0, "Index of object to extract.");
        options_string(ops, "in", &input_filename, "stdin", "input file (JSON)");
        options_string(ops, "out", &output_filename, "stdout", "output file (JSON)");
        
        if(!options_parse_args(ops, argc, argv)) {
                fprintf(stderr, "%s : extracts n-th JSON object from stream."
                        "\n\nOptions:\n", argv[0]);
                options_print_help(ops, stderr);
                return -1;
        }
        
        FILE * input_stream = open_file_for_reading(input_filename);
        FILE *output_stream = open_file_for_writing(output_filename);
        
        if(!input_stream || !output_stream) return -1;
        
        int i; for(i=0;i<nth;i++) {
                if(!json_stream_skip(input_stream)) {
                        sm_error("Could not skip %d-th object\n", i);
                        return -2;
                }
        }
        
        JO jo = json_read_stream(input_stream);
        if(!jo) {
                fprintf(stderr, "Could not read %d-th object (after skipping %d)\n", 
                        nth, i);
                return -2;
        }
        
        fputs(json_object_to_json_string(jo), output_stream);
        fputs("\n", output_stream);
        return 0;
}