用Capi连接mysql数据库的开发实例

1. 下载mysql c connector 安装包； 有两种方法： 1 下载tar文件， 将其中的的 lib， include ， bin 都放在 /usr/local 相应的目录下； 2. 也可配置链接库的附加目录 ： sudo vi /etc/ld.so.conf 文件中加入你的连接器的lib目录； 3. 好像也可以用 sudo apt

1. 下载mysql c connector 安装包； 有两种方法：

1 下载tar文件， 将其中的的 lib， include ， bin 都放在 /usr/local 相应的目录下；

2. 也可配置链接库的附加目录 ： sudo vi /etc/ld.so.conf 文件中加入你的连接器的lib目录；

3. 好像也可以用 sudo apt-get install libmysqclient-dev

对于c++的好像是 sudo apt-get install libmysql++-dev

2.编辑 C 程序利用mysql c api ： 我的程序如下：#include<mysql.h> #include<stdio.h> #include<stdlib.h> #include<string.h> static void output_error(MYSQL * mysql); int main(int argc, char* argv[]) { MYSQL mysql; MYSQL_RES * result; MYSQL_ROW row; MYSQL_FIELD * fields; const char* host = "localhost"; const char* user = "root"; const char* password = "root"; const char* database = "test"; const int port = 3306; const char* socket = NULL; const int flag = 0; const char* sql ; int num_fields; unsigned long * lengths; int i; //initialize the database if(!mysql_init(&mysql) ) { output_error(&mysql); } printf("mysql initialized successfully ! /n"); //connect to the database; if(!mysql_real_connect(&mysql, host, user, password, database, port, socket, flag)) { output_error(&mysql); } printf("mysql connect successfully! /n"); printf("/n/n/nthe content of the table data in the database test/n"); printf("-----------------------------------------------------------/n"); //do the select query on the database; sql = "select * from data" ; //printf("%d : %d/n", sizeof(sql), strlen(sql)); // 4：18 sizeof(sql):the size of point --(4); strlen(sql): if( mysql_real_query(&mysql, sql, strlen(sql)) ){ output_error(&mysql); } //fetch the the result set of the query! result = mysql_store_result(&mysql); if(result) { fields = mysql_fetch_fields(result); // fetch the struct of result num_fields = mysql_num_fields(result); // fetch the number of result fields; //lengths = mysql_fetch_lengths(result); for(i=0; i<num_fields; i++) { printf("%s/t", fields[i].name ); } printf("/n"); while(row = mysql_fetch_row(result)) { for(i=0; i<num_fields; i++) { printf("%s /t", row[i]); } printf("/n"); } //release the result of set for release the memory mysql_free_result(result); } else { output_error(&mysql); } printf("/n/n-----------------------------------------------------------/n"); //close the connetion to the database mysql_close(&mysql); return 0; } static void output_error(MYSQL * mysql) { fprintf(stderr, "errorno: %d /n", mysql_errno(mysql) ); fprintf(stderr, "error info: %s/n", mysql_error(mysql) ); exit(1); }

3. 编译 链接，测试：

wzb@wzb-desktop:~/test$ gcc -o db_test db_test.c -lmysql wzb@wzb-desktop:~/test$ ./db_test mysql initialized successfully ! mysql connect successfully! the content of the table data in the database test ----------------------------------------------------------- id nodeId data flag time 1 0 0 0 2011-03-31 18:19:40 2 1 1 2 2011-03-31 18:29:05 ----------------------------------------------------------- wzb@wzb-desktop:~/test$

注意链接动态库的选项　：　－lmysql

4.对mysql　ｃ开发几个有用的命令：ldd, mysql_config, file　，ｎm

ldd:　输出对动态库的依赖，即依赖的动态库的信息；

mysql_conf ：可以获得对mysql的配置开发的信息：　mysql_config -- libs

看一下，这几个命令的输出情况：

wzb@wzb-desktop:~/test$ ldd db_test linux-gate.so.1 => (0x00f40000) libmysql.so.16 => /usr/local/lib/libmysql.so.16 (0x0020f000) libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0x006bf000) libpthread.so.0 => /lib/tls/i686/cmov/libpthread.so.0 (0x004e4000) libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0x00110000) /lib/ld-linux.so.2 (0x00af6000) wzb@wzb-desktop:~/test$ file db_test db_test: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped wzb@wzb-desktop:~/test$ nm db_test 08049de4 d _DYNAMIC 08049ec0 d _GLOBAL_OFFSET_TABLE_ 08048c88 R _IO_stdin_used w _Jv_RegisterClasses 08049dd4 d __CTOR_END__ 08049dd0 d __CTOR_LIST__ 08049ddc d __DTOR_END__ 08049dd8 d __DTOR_LIST__ 08048dcc r __FRAME_END__ 08049de0 d __JCR_END__ 08049de0 d __JCR_LIST__ 08049f24 A __bss_start 08049f18 D __data_start 08048c40 t __do_global_ctors_aux 08048830 t __do_global_dtors_aux 08049f1c D __dso_handle w __gmon_start__ 08048c3a T __i686.get_pc_thunk.bx 08049dd0 d __init_array_end 08049dd0 d __init_array_start 08048bd0 T __libc_csu_fini 08048be0 T __libc_csu_init U __libc_start_main@@GLIBC_2.0 U __stack_chk_fail@@GLIBC_2.4 08049f24 A _edata 08049f2c A _end 08048c68 T _fini 08048c84 R _fp_hw 08048684 T _init 08048800 T _start 08049f28 b completed.5790 08049f18 W data_start U exit@@GLIBC_2.0 U fprintf@@GLIBC_2.0 08048860 t frame_dummy 08048884 T main U mysql_close U mysql_errno U mysql_error U mysql_fetch_fields U mysql_fetch_row U mysql_free_result U mysql_init U mysql_num_fields U mysql_real_connect U mysql_real_query U mysql_store_result 08048b66 t output_error 08049f20 d p.5788 U printf@@GLIBC_2.0 U putchar@@GLIBC_2.0 U puts@@GLIBC_2.0 08049f24 B stderr@@GLIBC_2.0 wzb@wzb-desktop:~/test$

wzb@wzb-desktop:~/test$ mysql_config Copyright 2009 Sun Microsystems, Inc. This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL license Get compiler flags for using the MySQL client library. Usage: mysql_config [OPTIONS] --cflags [-I/usr/local/include] -?, --help Display this help and exit. --include [-I/usr/local/include] --libs [-L/usr/local/lib -lmysql -lpthread] --libs_r [-L/usr/local/lib -lmysql -lpthread] --version [6.0.2] wzb@wzb-desktop:~/test$ mysql_config --libs -L/usr/local/lib -lmysql -lpthread wzb@wzb-desktop:~/test$ mysql_config --libs_r -L/usr/local/lib -lmysql -lpthread wzb@wzb-desktop:~/test$ mysql_config --include -I/usr/local/include wzb@wzb-desktop:~/test$

下文的链接：http://www.cyberciti.biz/tips/linux-unix-connect-mysql-c-api-program.html

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Howto: Connect MySQL server using C program API under Linux or UNIX

by Vivek Gite on May 31, 2007 · 56 comments

From my mailbag:

How do I write a C program to connect MySQL database server?

MySQL database does support C program API just like PHP or perl.

The C API code is distributed with MySQL. It is included in the mysqlclient library and allows C programs to access a database.

Many of the clients in the MySQL source distribution are written in C. If you are looking for examples that demonstrate how to use the C API, take a look at these clients. You can find these in the clients directory in the MySQL source distribution.

Requirements

Make sure you have development environment installed such as gcc, mysql development package etc. Following is the list summarize the list of packages to compile program:

• mysql: MySQL client programs and shared library
• mysqlclient: Backlevel MySQL shared libraries (old libs)
• mysql-devel: Files for development of MySQL applications (a must have)
• mysql-server: Mysql server itself
• gcc, make and other development libs: GNU C compiler

Sample C Program

Following instructions should work on any Linux distro or UNIX computer. Here is the small program that connects to mysql server and list tables from mysql database.(download link):

* Simple C program that connects to MySQL Database server*/ #include <mysql.h> #include <stdio.h> main() { MYSQL *conn; MYSQL_RES *res; MYSQL_ROW row; char *server = "localhost"; char *user = "root"; char *password = "PASSWORD"; /* set me first */ char *database = "mysql"; conn = mysql_init(NULL); /* Connect to database */ if (!mysql_real_connect(conn, server, user, password, database, 0, NULL, 0)) { fprintf(stderr, "%s/n", mysql_error(conn)); exit(1); } /* send SQL query */ if (mysql_query(conn, "show tables")) { fprintf(stderr, "%s/n", mysql_error(conn)); exit(1); } res = mysql_use_result(conn); /* output table name */ printf("MySQL Tables in mysql database:/n"); while ((row = mysql_fetch_row(res)) != NULL) printf("%s /n", row[0]); /* close connection */ mysql_free_result(res); mysql_close(conn); }

How do I compile and link program against MySQL libs?

MySQL comes with a special script called mysql_config. It provides you with useful information for compiling your MySQL client and connecting it to MySQL database server. You need to use following two options.
Pass --libs option - Libraries and options required to link with the MySQL client library.

$ mysql_config --libs
Output:

-L/usr/lib64/mysql -lmysqlclient -lz -lcrypt -lnsl -lm -L/usr/lib64 -lssl -lcrypto

Pass --cflags option - Compiler flags to find include files and critical compiler flags and defines used when compiling the libmysqlclient library.
$ mysql_config --cflags
Output:

-I/usr/include/mysql -g -pipe -m64 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing

You need to pass above option to GNU C compiler i.e. gcc. So to compile above program, enter:
$ gcc -o output-file $(mysql_config --cflags)mysql-c-api.c $(mysql_config --libs)
Now execute program:
$ ./output-file
Output:

MySQL Tables in mysql database:


columns_priv


db


func


help_category


help_keyword


help_relation


help_topic


host


tables_priv


time_zone


time_zone_leap_second


time_zone_name


time_zone_transition


time_zone_transition_type


user 

References:

• MySQL C API - A must read - official MySQL C API documentation

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