feat: update postgres

postgres.c

@@ -10,12 +10,14 @@
 
 static PGconn *conn;
 
-int pg_connect(char *args) {
-  if (args == NULL) {
+int pg_connect(char **args) {
+  if (args[2] == NULL) {
     fprintf(stderr, "pg connect: need dbname\n");
     return 1;
   }
-  conn = PQsetdbLogin("localhost", "5432", NULL, NULL, args, "postgres", NULL);
+  /* Make a connection to the database */
+  conn = PQsetdbLogin("localhost", "5432", NULL, NULL, args[2], "postgres", NULL);
+  /* Check to see that the backend connection was successfully made */
   if (PQstatus(conn) == CONNECTION_BAD) {
     fprintf(stderr, "pg connect: Connection to database failed: %s",
             PQerrorMessage(conn));
@@ -28,14 +30,17 @@ int pg_list() {
     fprintf(stderr, "pg list: not connected to database\n");
     return 1;
   }
+  /* Declare a PGresult pointer */
   PGresult *res =
       PQexec(conn, "SELECT table_name FROM information_schema.tables WHERE "
                    "table_schema = 'public'");
+  /* Check to see that the result is successful */
   if (PQresultStatus(res) != PGRES_TUPLES_OK) {
     fprintf(stderr, "pg list: No data retrieved\n");
     PQclear(res);
     return 1;
   }
+  /* print out the rows */
   int rows = PQntuples(res);
   for (int i = 0; i < rows; i++) {
     if (i != 0)
@@ -46,34 +51,36 @@ int pg_list() {
   return 0;
 }
 
-int pg_show(char *args) {
+int pg_show(char **args) {
   if (conn == NULL) {
     fprintf(stderr, "pg show: not connected to database\n");
     return 1;
   }
-  if (args == NULL) {
-    fprintf(stderr, "pg show: need table name\n");
+  if (args[2] == NULL) {
+    fprintf(stderr, \
+    "pg show: need table name\n\
+    eg: pg show table_name\n");
     return 1;
   }
-  char *query = malloc(100);
-  sprintf(query, "SELECT * FROM %s", args);
+
+  char query[LINE_BUF_SIZE];
+  sprintf(query, "SELECT * FROM %s", args[2]);
   PGresult *res = PQexec(conn, query);
   if (PQresultStatus(res) != PGRES_TUPLES_OK) {
     fprintf(stderr, "pg show: No data retrieved\n");
     PQclear(res);
     return 1;
   }
+  /*neatly print the entire table*/
   int rows = PQntuples(res);
   int cols = PQnfields(res);
 
-  //print header
   for (int i = 0; i < cols; i++) {
     if (i != 0)
       printf(", ");
     printf("%s ", PQfname(res, i));
   }
   printf("\n");
-  //print whole table
   for (int i = 0; i < rows; i++) {
     for (int j = 0; j < cols; j++) {
       if (j != 0)
@@ -82,10 +89,49 @@ int pg_show(char *args) {
     }
     printf("\n");
   }
+  return 0;
+}
 
+int pg_insert(char **args) {
 
+  return 0;
+}
+
+int pg_run(char **args) {
+  if (conn == NULL) {
+    fprintf(stderr, "pg run: not connected to database\n");
+    return 1;
+  }
+  if (args[2] == NULL) {
+    fprintf(stderr, \
+    "pg run: need command\n\
+    eg: pg run \"SELECT * FROM table_name\"\n");
+    return 1;
+  }
+  PGresult *res = PQexec(conn, args[2]);
+  if (PQresultStatus(res) != PGRES_TUPLES_OK) {
+    fprintf(stderr, "pg run: No data retrieved\n");
+    PQclear(res);
+    return 1;
+  }
+  /*neatly print the result*/
+  int rows = PQntuples(res);
+  int cols = PQnfields(res);
+
+  for (int i = 0; i < cols; i++) {
+    if (i != 0)
+      printf(", ");
+    printf("%s ", PQfname(res, i));
+  }
   printf("\n");
-  free(query);
+  for (int i = 0; i < rows; i++) {
+    for (int j = 0; j < cols; j++) {
+      if (j != 0)
+        printf(", ");
+      printf("%s ", PQgetvalue(res, i, j));
+    }
+    printf("\n");
+  }
   return 0;
 }
 
@@ -94,21 +140,43 @@ int dish_pg(char **args) {
     fprintf(stderr, "pg: need arguments\n\
     possible arguments:\n\
     connect: connect to database\n\
+    disconnect: disconnect from database\n\
     list: list all tables\n\
-    show: show all contents of a table\n");
+    show: show all contents of a table\n\
+    insert: insert into a table\n\
+    delete: delete from a table\n\
+    run: run a custom command\n");
     return 1;
   }
   if (strcmp(args[1], "connect") == 0) {
-    pg_connect(args[2]);
-  }
-  if (strcmp(args[1], "list") == 0) {
-    pg_list();
-  }
-  if (strcmp(args[1], "show") == 0) {
-    pg_show(args[2]);
+    return pg_connect(args);
   }
 
+  else if (strcmp(args[1], "disconnect") == 0) {
+    if (conn != NULL) {
+      PQfinish(conn);
       return 0;
     }
+    fprintf(stderr, "pg disconnect: not connected to database\n");
+    return 1;
+
+  } else if (strcmp(args[1], "list") == 0) {
+    return pg_list();
+
+  } else if (strcmp(args[1], "show") == 0) {
+    return pg_show(args);
+
+  } else if (strcmp(args[1], "insert") == 0) {
+    return pg_insert(args);
+    
+  } else if(strcmp(args[1],"run")==0)
+  {
+    return pg_run(args);
+  }
+   else
+    fprintf(stderr, "pg: invalid argument\n");
+
+  return 1;
+}
 
 #endif