feat: add prepared_statement

main
dancesWithCycles 2023-01-05 15:30:31 +01:00
parent 731a8ab59d
commit fbc1b118ca
3 changed files with 140 additions and 0 deletions

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#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;
}

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# 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) *~

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* 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"
```