feat: add example1

example1/main.c

@@ -0,0 +1,123 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+
+static void
+exit_nicely(PGconn *conn)
+{
+    PQfinish(conn);
+    exit(1);
+}
+
+int
+main(int argc, char **argv)
+{
+    const char *conninfo;
+    PGconn     *conn;
+    PGresult   *res;
+    int         nFields;
+    int         i,
+                j;
+
+    printf("main() Started...\n");
+    /*
+     * If the user supplies a parameter on the command line, use it as the
+     * conninfo string; otherwise default to setting dbname=postgres and using
+     * environment variables or defaults for all other connection parameters.
+     */
+    if (argc > 1){
+      printf("main() argv[1]: %s\n", argv[1]);
+      conninfo = argv[1];
+    }else{
+      conninfo = "dbname = postgres";
+    }
+
+    /* Make a connection to the database */
+    conn = PQconnectdb(conninfo);
+
+    if(conn==NULL){
+      printf("main() connection object NOT available\n");
+    }else{
+      printf("main() connection object available\n");
+    }
+
+    /* Check to see that the backend connection was successfully made */
+    if (PQstatus(conn) != CONNECTION_OK)
+      {
+        fprintf(stderr, "Connection to database failed: %s",
+                PQerrorMessage(conn));
+        exit_nicely(conn);
+    }
+
+    /*
+     * Our test case here involves using a cursor, for which we must be inside
+     * a transaction block.  We could do the whole thing with a single
+     * PQexec() of "select * from pg_database", but that's too trivial to make
+     * a good example.
+     */
+
+    /* Start a transaction block */
+    res = PQexec(conn, "BEGIN");
+    if (PQresultStatus(res) != PGRES_COMMAND_OK)
+    {
+        fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
+        PQclear(res);
+        exit_nicely(conn);
+    }
+
+    /*
+     * Should PQclear PGresult whenever it is no longer needed to avoid memory
+     * leaks
+     */
+    PQclear(res);
+
+    /*
+     * Fetch rows from pg_database, the system catalog of databases
+     */
+    res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
+    if (PQresultStatus(res) != PGRES_COMMAND_OK)
+    {
+        fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
+        PQclear(res);
+        exit_nicely(conn);
+    }
+    PQclear(res);
+
+    res = PQexec(conn, "FETCH ALL in myportal");
+    if (PQresultStatus(res) != PGRES_TUPLES_OK)
+    {
+        fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
+        PQclear(res);
+        exit_nicely(conn);
+    }
+
+    /* first, print out the attribute names */
+    nFields = PQnfields(res);
+    for (i = 0; i < nFields; i++)
+        printf("%-15s", PQfname(res, i));
+    printf("\n\n");
+
+    /* next, print out the rows */
+    for (i = 0; i < PQntuples(res); i++)
+    {
+        for (j = 0; j < nFields; j++)
+            printf("%-15s", PQgetvalue(res, i, j));
+        printf("\n");
+    }
+
+    PQclear(res);
+
+    /* close the portal ... we don't bother to check for errors ... */
+    res = PQexec(conn, "CLOSE myportal");
+    PQclear(res);
+
+    /* end the transaction */
+    res = PQexec(conn, "END");
+    PQclear(res);
+
+    /* close the connection to the database and cleanup */
+    PQfinish(conn);
+
+    printf("main() Done.\n");
+    return 0;
+}

example1/makefile

@@ -0,0 +1,21 @@
+# Docu
+#
+#$@ is the name of the file to be made
+#$? is the names of the changed dependents
+#$< the name of the related file that caused the action
+#$* the prefix shared by target and dependent files
+#
+# Others
+RM      = /bin/rm -f
+#
+# Source, Executable, Includes, Library Defines
+EXE    = main
+#
+# Compiler, Linker Defines
+CC      = /usr/bin/gcc
+#
+all:
+	$(CC) main.c -I/usr/include/postgresql -L/usr/lib/x86_64-linux-gnu -lpq -std=c99 -Wall -o $(EXE)
+# Clean Up Objects, Exectuables, Dumps out of source directory
+clean:
+	$(RM) *.o $(EXE) *~

example1/readme.md

@@ -0,0 +1,17 @@
+* build
+
+```
+make
+```
+
+* run
+
+```
+./main 'postgresql://begerad:secret@localhost:5432/sib00_vbn_gtfs'
+```
+
+* or run
+
+```
+./main 'postgresql://begerad:secret@localhost:5432/vbn_data'
+```