本文共 1970 字，大约阅读时间需要 6 分钟。

安装库

sudo apt-get install opensslsudo apt-get install libssl-dev

编写程序

//gcc -g str_md5_demo.c -o str_md5_demo -lcrypto//#include 
   
    #include 
    
     #include 
     
       int main(int argc, char* argv[]){
       MD5_CTX ctx;    unsigned char md[16] = {
   0};    int i = 0;     //方法一:    MD5_Init(&ctx);    MD5_Update(&ctx, "hel", 3);    MD5_Update(&ctx, "lo", 2);    MD5_Final(md, &ctx);     for (i = 0; i < 16; i++)        printf("%02X", md[i]);    printf("\n");     //方法二:    const char data[] = "hello";    MD5(data, strlen(data), md);     for (i = 0; i < 16; i++)        printf("%02X", md[i]);    printf("\n");     return 0;}
     
    
   

//gcc -g file_md5_demo.c -o file_md5_demo -lcrypto// #include 
   
    #include 
    
     #include 
     
       int main(int argc, char* argv[]){
       MD5_CTX ctx;    unsigned char md[16] = {
   0};    char buffer[1024] = {
   0};    char filename[64] = {
   0};    int len = 0, i;    FILE* fp = NULL;     printf("请输入文件名, 用于计算MD5值\n");    scanf("%s", filename);     fp = fopen(filename, "rb");    if(NULL == fp){
           printf("can't open file\n");        return 1;    }     //方法一:    MD5_Init(&ctx);    while((len=fread(buffer, 1, sizeof(buffer), fp)) > 0){
           MD5_Update(&ctx, buffer, len);        memset(buffer, 0 ,sizeof(buffer));    }    MD5_Final(md, &ctx);     for(i=0; i<16; i++)        printf("%02X", md[i]);    printf("\n");     //方法二:    while((len=fread(buffer, 1, sizeof(buffer), fp)) > 0){
           MD5(buffer, len, md);        memset(buffer, 0 ,sizeof(buffer));    }     for(i=0; i<16; i++)        printf("%02X", md[i]);    printf("\n");     if(fp) fclose(fp);     return 0;}
     
    
   

编写Makefile

注意：在Ubuntu 14.04 64bit上一定要需要链接 -lcrypto

INCLUDES = -I. -I /usr/include/http-testSRCS = http-test.cOBJS = $(SRCS:.c=.o)CC = gccCFLAGS = -Wall -O -gLIBS = -lpthread -lcryptoEXE = http-test$(EXE):$(OBJS)	$(CC) $^ -o $@ $(LIBS)%.o: %.c	$(CC) $(CFLAGS) $(INCLUDES) -c $< -o $@clean:	rm -f $(EXE) $(OBJS)

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