用C api 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-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：

[cpp] view plaincopyprint?

1. #include<mysql.h> 
2. #include<stdio.h> 
3. #include<stdlib.h> 
4. #include<string.h> 
5. static void output_error(MYSQL * mysql); 
6. int main(int argc,char* argv[]) { 
7.      MYSQL mysql; 
8.      MYSQL_RES * result; 
9.      MYSQL_ROW row; 
10.      MYSQL_FIELD * fields; 
11.     const char* host ="localhost"; 
12.     const char* user ="root"; 
13.     const char* password ="root"; 
14.     const char* database ="test"; 
15.     const int   port = 3306; 
16.     const char* socket = NULL; 
17.     const int flag = 0; 
18.     const char* sql ;    
19.     int num_fields; 
20.     unsigned long * lengths; 
21.     int i; 
22.     //initialize the database  
23.     if(!mysql_init(&mysql) ) { 
24.         output_error(&mysql); 
25.     } 
26.     printf("mysql initialized successfully ! /n"); 
27.     //connect to the database; 
28.     if(!mysql_real_connect(&mysql, host, user, password, database, port, socket, flag)) { 
29.         output_error(&mysql); 
30.     } 
31.     printf("mysql connect successfully! /n"); 
32.     printf("/n/n/nthe content of the table data in the database test/n"); 
33.     printf("-----------------------------------------------------------/n"); 
34.     //do the select query on the database; 
35.     sql = "select * from data" ; 
36.     //printf("%d : %d/n", sizeof(sql), strlen(sql)); // 4：18 sizeof(sql):the size of point --(4); strlen(sql): 
37.     if( mysql_real_query(&mysql, sql, strlen(sql)) ){ 
38.         output_error(&mysql); 
39.     } 
40.     //fetch the the result set of the query!        
41.     result = mysql_store_result(&mysql); 
42.     if(result) { 
43.         fields = mysql_fetch_fields(result);    // fetch the struct of result         
44.         num_fields = mysql_num_fields(result);  // fetch the number of result fields; 
45.          
46.         //lengths = mysql_fetch_lengths(result);    
47.         for(i=0; i<num_fields; i++) { 
48.             printf("%s/t", fields[i].name ); 
49.         } 
50.         printf("/n"); 
51.         while(row = mysql_fetch_row(result)) { 
52.             for(i=0; i<num_fields; i++) { 
53.                 printf("%s /t",  row[i]); 
54.              } 
55.              printf("/n"); 
56.         } 
57.         //release the result of set  for release the memory 
58.         mysql_free_result(result);   
59.          
60.     } 
61.     else { 
62.         output_error(&mysql); 
63.     } 
64.     printf("/n/n-----------------------------------------------------------/n"); 
65.     //close the connetion to the database 
66.     mysql_close(&mysql); 
67.     return 0; 
68. } 
69. static void output_error(MYSQL * mysql) { 
70.     fprintf(stderr, "errorno: %d /n", mysql_errno(mysql) ); 
71.     fprintf(stderr, "error info: %s/n", mysql_error(mysql) ); 
72.     exit(1); 
73. } 

#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 memorymysql_free_result(result);}else {output_error(&mysql);}printf("/n/n-----------------------------------------------------------/n");//close the connetion to the databasemysql_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：

[c-sharp] view plaincopyprint?

1. wzb@wzb-desktop:~/test$ gcc -o db_test db_test.c -lmysql  
2. wzb@wzb-desktop:~/test$ ./db_test 
3. mysql initialized successfully !  
4. mysql connect successfully!  
5. the content of the table data in the database test 
6. ----------------------------------------------------------- 
7. id  nodeId  data    flag    time     
8. 1   0   0   0   2011-03-31 18:19:40      
9. 2   1   1   2   2011-03-31 18:29:05      
10. ----------------------------------------------------------- 
11. wzb@wzb-desktop:~/test$  

wzb@wzb-desktop:~/test$ gcc -o db_test db_test.c -lmysql wzb@wzb-desktop:~/test$ ./db_testmysql initialized successfully ! mysql connect successfully! the content of the table data in the database test-----------------------------------------------------------idnodeIddataflagtime1 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：

[c-sharp] view plaincopyprint?

1. wzb@wzb-desktop:~/test$ ldd db_test 
2.     linux-gate.so.1 =>  (0x00f40000) 
3.     libmysql.so.16 => /usr/local/lib/libmysql.so.16 (0x0020f000) 
4.     libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0x006bf000) 
5.     libpthread.so.0 => /lib/tls/i686/cmov/libpthread.so.0 (0x004e4000) 
6.     libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0x00110000) 
7.     /lib/ld-linux.so.2 (0x00af6000) 
8. wzb@wzb-desktop:~/test$ file db_test 
9. 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 
10. wzb@wzb-desktop:~/test$ nm db_test 
11. 08049de4 d _DYNAMIC 
12. 08049ec0 d _GLOBAL_OFFSET_TABLE_ 
13. 08048c88 R _IO_stdin_used 
14.          w _Jv_RegisterClasses 
15. 08049dd4 d __CTOR_END__ 
16. 08049dd0 d __CTOR_LIST__ 
17. 08049ddc d __DTOR_END__ 
18. 08049dd8 d __DTOR_LIST__ 
19. 08048dcc r __FRAME_END__ 
20. 08049de0 d __JCR_END__ 
21. 08049de0 d __JCR_LIST__ 
22. 08049f24 A __bss_start 
23. 08049f18 D __data_start 
24. 08048c40 t __do_global_ctors_aux 
25. 08048830 t __do_global_dtors_aux 
26. 08049f1c D __dso_handle 
27.          w __gmon_start__ 
28. 08048c3a T __i686.get_pc_thunk.bx 
29. 08049dd0 d __init_array_end 
30. 08049dd0 d __init_array_start 
31. 08048bd0 T __libc_csu_fini 
32. 08048be0 T __libc_csu_init 
33.          U __libc_start_main@@GLIBC_2.0 
34.          U __stack_chk_fail@@GLIBC_2.4 
35. 08049f24 A _edata 
36. 08049f2c A _end 
37. 08048c68 T _fini 
38. 08048c84 R _fp_hw 
39. 08048684 T _init 
40. 08048800 T _start 
41. 08049f28 b completed.5790 
42. 08049f18 W data_start 
43.          U exit@@GLIBC_2.0 
44.          U fprintf@@GLIBC_2.0 
45. 08048860 t frame_dummy 
46. 08048884 T main 
47.          U mysql_close 
48.          U mysql_errno 
49.          U mysql_error 
50.          U mysql_fetch_fields 
51.          U mysql_fetch_row 
52.          U mysql_free_result 
53.          U mysql_init 
54.          U mysql_num_fields 
55.          U mysql_real_connect 
56.          U mysql_real_query 
57.          U mysql_store_result 
58. 08048b66 t output_error 
59. 08049f20 d p.5788 
60.          U printf@@GLIBC_2.0 
61.          U putchar@@GLIBC_2.0 
62.          U puts@@GLIBC_2.0 
63. 08049f24 B stderr@@GLIBC_2.0 
64. wzb@wzb-desktop:~/test$  

wzb@wzb-desktop:~/test$ ldd db_testlinux-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_testdb_test: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not strippedwzb@wzb-desktop:~/test$ nm db_test08049de4 d _DYNAMIC08049ec0 d _GLOBAL_OFFSET_TABLE_08048c88 R _IO_stdin_used w _Jv_RegisterClasses08049dd4 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_start08049f18 D __data_start08048c40 t __do_global_ctors_aux08048830 t __do_global_dtors_aux08049f1c D __dso_handle w __gmon_start__08048c3a T __i686.get_pc_thunk.bx08049dd0 d __init_array_end08049dd0 d __init_array_start08048bd0 T __libc_csu_fini08048be0 T __libc_csu_init U __libc_start_main@@GLIBC_2.0 U __stack_chk_fail@@GLIBC_2.408049f24 A _edata08049f2c A _end08048c68 T _fini08048c84 R _fp_hw08048684 T _init08048800 T _start08049f28 b completed.579008049f18 W data_start U exit@@GLIBC_2.0 U fprintf@@GLIBC_2.008048860 t frame_dummy08048884 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_result08048b66 t output_error08049f20 d p.5788 U printf@@GLIBC_2.0 U putchar@@GLIBC_2.0 U puts@@GLIBC_2.008049f24 B stderr@@GLIBC_2.0wzb@wzb-desktop:~/test$

[c-sharp] view plaincopyprint?

1. wzb@wzb-desktop:~/test$ mysql_config 
2. Copyright 2009 Sun Microsystems, Inc. 
3. This software comes with ABSOLUTELY NO WARRANTY. This is free software, 
4. and you are welcome to modify and redistribute it under the GPL license 
5. Get compiler flags for using the MySQL client library. 
6. Usage: mysql_config [OPTIONS] 
7.   --cflags            [-I/usr/local/include] 
8.   -?, --help          Display this help and exit. 
9.   --include           [-I/usr/local/include] 
10.   --libs              [-L/usr/local/lib -lmysql -lpthread] 
11.   --libs_r            [-L/usr/local/lib -lmysql -lpthread] 
12.   --version           [6.0.2] 
13. wzb@wzb-desktop:~/test$ mysql_config --libs 
14. -L/usr/local/lib -lmysql -lpthread 
15. wzb@wzb-desktop:~/test$ mysql_config --libs_r 
16. -L/usr/local/lib -lmysql -lpthread 
17. wzb@wzb-desktop:~/test$ mysql_config --include 
18. -I/usr/local/include 
19. wzb@wzb-desktop:~/test$  

wzb@wzb-desktop:~/test$ mysql_configCopyright 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 licenseGet 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 -lpthreadwzb@wzb-desktop:~/test$ mysql_config --libs_r-L/usr/local/lib -lmysql -lpthreadwzb@wzb-desktop:~/test$ mysql_config --include-I/usr/local/includewzb@wzb-desktop:~/test$

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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):

[cpp] view plaincopyprint?

1. * Simple C program that connects to MySQL Database server*/ 
2. #include <mysql.h> 
3. #include <stdio.h> 
4. main() { 
5.    MYSQL *conn; 
6.    MYSQL_RES *res; 
7.    MYSQL_ROW row; 
8.    char *server = "localhost"; 
9.    char *user = "root"; 
10.    char *password = "PASSWORD";/* set me first */ 
11.    char *database = "mysql"; 
12.    conn = mysql_init(NULL); 
13.    /* Connect to database */ 
14.    if (!mysql_real_connect(conn, server, 
15.          user, password, database, 0, NULL, 0)) { 
16.       fprintf(stderr, "%s/n", mysql_error(conn)); 
17.       exit(1); 
18.    } 
19.    /* send SQL query */ 
20.    if (mysql_query(conn, "show tables")) { 
21.       fprintf(stderr, "%s/n", mysql_error(conn)); 
22.       exit(1); 
23.    } 
24.    res = mysql_use_result(conn); 
25.    /* output table name */ 
26.    printf("MySQL Tables in mysql database:/n"); 
27.    while ((row = mysql_fetch_row(res)) != NULL) 
28.       printf("%s /n", row[0]); 
29.    /* close connection */ 
30.    mysql_free_result(res); 
31.    mysql_close(conn); 
32. } 

* 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_privdbfunchelp_categoryhelp_keywordhelp_relationhelp_topichosttables_privtime_zonetime_zone_leap_secondtime_zone_nametime_zone_transitiontime_zone_transition_typeuser 

References:

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