feat: add prepared_statement

prepared_statement/main.c

@@ -0,0 +1,93 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+
+void do_exit(PGconn *conn) {
+  PQfinish(conn);
+  exit(1);
+}
+
+int main(int argc, char *argv[]) {
+  /*declaration*/
+  const char *conninfo;
+  const int LEN = 10;
+  const char *paramValues[1];
+
+  printf("main() Started...\n");
+  if (argc != 3) {
+    fprintf(stderr, "Usage: ./main <row id> <connection info>\n");
+    exit(1);
+  }
+
+  printf("main() argv[1]: %s\n", argv[1]);
+  int rowId;
+
+  /*store command line argument in int variable*/
+  /*validate user input*/
+  /*omit SQL injection*/
+  /*stream:argv*/
+  int ret = sscanf(argv[1], "%d", &rowId);
+
+  /*valid user input:1 successfully filled item*/
+  if (ret != 1) {
+    fprintf(stderr, "The argument must be an integer\n");
+    exit(1);
+  }
+
+  if (rowId < 0) {
+    fprintf(stderr, "Error passing a negative rowId\n");
+    exit(1);
+  }
+
+  printf("main() LEN: %d\n", LEN);
+  char str[LEN];
+  printf("main() str.length: %ld\n", sizeof(str));
+  snprintf(str, LEN, "%d", rowId);
+  printf("main() str: %s\n", str);
+  paramValues[0] = str;  
+    
+  /*read command line*/
+  printf("main() argv[2]: %s\n", argv[2]);
+  conninfo = argv[2];
+
+  /*connect to database*/
+  PGconn *conn = PQconnectdb(conninfo);
+  if (PQstatus(conn) == CONNECTION_BAD) {
+    fprintf(stderr, "Connection to database failed: %s\n",
+            PQerrorMessage(conn));
+    PQfinish(conn);
+    exit(1);
+  }else if(PQstatus(conn)==CONNECTION_OK){
+    printf("main() connected to database\n");
+  }else{
+    printf("main() connection status NOT known\n");
+  }
+
+  char *stm = "SELECT * FROM cars_cleanup WHERE Id=$1";
+
+  /*create prepared statement*/
+  /*conn:connection*/
+  /*stm:statement*/
+  /*1:number of passed parameters*/
+  /*NULL: server figures out parameter type*/
+  /*paramValues:pointer of an array of strings containing parameters*/
+  /*NULL:relevant for binary parameters*/
+  /*NULL:relevant for binary parameters*/
+  /*0:obtain result in text format*/
+  PGresult *res = PQexecParams(conn, stm, 1, NULL, paramValues, 
+        NULL, NULL, 0);
+
+  if (PQresultStatus(res) != PGRES_TUPLES_OK) {
+    printf("No data retrieved\n");
+    PQclear(res);
+    do_exit(conn);
+  }
+
+  printf("%s %s %s\n", PQgetvalue(res, 0, 0),
+	 PQgetvalue(res, 0, 1), PQgetvalue(res, 0, 2));
+  PQclear(res);
+
+  PQfinish(conn);
+  return 0;
+}
+    

prepared_statement/makefile

@@ -0,0 +1,24 @@
+# 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: main.o
+	$(CC) main.c -I/usr/include/postgresql -L/usr/lib/x86_64-linux-gnu -lpq -std=c99 -Wall -o $(EXE)
+#
+main.o:
+	$(CC) -c main.c -I/usr/include/postgresql
+# Clean Up Objects, Exectuables, Dumps out of source directory
+clean:
+	$(RM) *.o $(EXE) *~

prepared_statement/readme.md

@@ -0,0 +1,23 @@
+* build
+
+```
+make
+```
+
+* run
+
+```
+./main 'postgresql://begerad:secret@localhost:5432/sib00_vbn_gtfs'
+```
+
+* or run
+
+```
+./main 'postgresql://begerad:secret@localhost:5432/vbn_data'
+```
+
+* or run
+
+```
+./main "host=localhost port=5432 user=begerad password=<secret> dbname=vbn_data"
+```