我需要将文本的十六进制保存为字符串：

_____________________
Input: apple

Output: 6170706c65
_____________________

char * text = "apple";
char * hextext = convertToHex(text); // -> ?! I don't know how

printf("Hextext is %s\n", hextext); // -> Hextext is 6170706c65

和

char * hextext = 6170706c65;
char * text = convertToText(hextext);

printf("Text is %s\n", text);

使用Printf，使用%hx很容易，但我需要变量上的值！
有人能帮帮忙吗？！谢谢。
我的最终代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void convertToHex(char* input, char** output)
{
    char* ptr;
    int i;

    // Allocate memory for hex string
    *output = malloc(2 * strlen(input) + 1);

    // Initialize pointer to start of the output buffer
    ptr = *output;

    // Read each char in input. Use sprintf to append the 2 char hex value.
    // Finally advance the pointer 2 places in the output buffer.
    for(i=0; i<strlen(input); i++) 
    {
        sprintf(ptr, "%x", input[i]);
        ptr++; ptr++;
    }
}

void convertHexToString(char* input, char** output)
{
    char* ptr;
    int c;

    // Allocate memory for hex string
    *output = malloc(2 * (strlen(input)/2)%2==0 ? (strlen(input)/2) + 1 : (strlen(input)/2));

    // Initialize pointer to start of the output buffer
    ptr = *output;

    // Read two char in input. Use sprintf to append the char value.
    // Finally advance the input place in the output buffer.
    for (;input[0] && input[1] && sscanf(input, "%2x", &c); input += 2) 
    {
        sprintf(ptr, "%c", c);
        ptr++;
    }
}

int main(void)
{
    char* text = "apple";
    char* hexkey;
    char* strtext;

    convertToHex(text, &hexkey);

    printf("Input: %s\n", text);
    printf("Output: %s\n", hexkey);

    convertHexToString(hexkey, &strtext);

    printf("\nInput2: %s\n", hexkey);
    printf("Output2: %s\n", strtext);

    free(hexkey);
    free(strtext);

    return 0;
}

特别感谢Erik Nedwidek的帮助！