C by Example: GDBM

gdbm_example.c

// gdbm_example.c
// CFLAGS = -Wall -Wextra -Werror -O2 -std=c99 -pedantic -lGDBM

#include <stdio.h>
#include <string.h>
#include <gdbm.h>
#include <stdlib.h>

GDBM_FILE dbf;

void read(char * keyStr) {
	extern GDBM_FILE dbf;
	datum key = {keyStr, strlen(keyStr)};
	datum data = gdbm_fetch(dbf, key);
	fprintf(stdout, "%s\n", data.dptr);
	free(data.dptr);
}

void write(char * keyStr, char * valueStr) {
	extern GDBM_FILE dbf;
	datum key = {keyStr, strlen(keyStr)};
	datum data = {valueStr, strlen(valueStr)};
	gdbm_store(dbf, key, data, GDBM_REPLACE);
}

void delete(char * keyStr) {
	extern GDBM_FILE dbf;
	datum key = {keyStr, strlen(keyStr)};
	int err = gdbm_delete(dbf, key);
	if(err == -1) {
		fprintf(stderr, "%s not present", keyStr);
	}
}

int main (int argc, char *argv[])
{
	extern GDBM_FILE gdf;

	if(argc < 3) {
		printf("Usage: %s DB_FILE [read|write|delete] [KEY] [VALUE]\n\n", argv[0]);
		exit(1);
	}

	dbf = gdbm_open(argv[1], 0, GDBM_WRCREAT | GDBM_NOLOCK | GDBM_SYNC, 0664, 0);
	if(!dbf){
		fprintf(stderr, "Failed to create/read from %s", argv[1]);
		exit(2);
	}

	if(argc == 4 && strcmp(argv[2], "read") == 0) {
		read(argv[3]);
	}else if(argc == 5 && strcmp(argv[2],"write") == 0) {
		write(argv[3], argv[4]);
	}else if(argc == 4 && strcmp(argv[2], "delete") == 0) {
		delete(argv[3]);
	}else{
		printf("Usage: %s [read|write] [KEY] [VALUE]\n\n", argv[0]);
		exit(1);
	}

	gdbm_close(dbf);
	return 0;
}