C String splitting examples

strsep.c

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

void split_in_two(const char* input)
{
    // we first make a copy of the input. We don't have to,
    // but strsep operates by overwriting the delimiter in the
    // input string, and I want to keep it clean.
    // you can remove that step if you're okay with trashing
    // the original.
    char* source = malloc(strlen(input) + 1);
    if (!source)
        abort();
    strcpy(source, input);

    char left[50], right[50];

    // we start at the start
    char* cursor = source;

    // get the first one.
    // note, strsep replaces the delimiter '|' in the string with a '\0',
    // so strcpy will stop at the right spot.
    strcpy(left, strsep(&cursor, "|"));

    // at this point, cursor will point to the start to the second part,
    // or NULL if there's nothing left
    if (!cursor)
        return;
    
    strcpy(right, strsep(&cursor, "|"));

    printf(
        "Left: %s\n"
        "Right: %s\n",
        left, right
    );

    free(source);
}

int main(void)
{
    split_in_two("Hello|World");
}

strtok_r.c

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

// Microsoft's version of strtok_r is called strtok_s
#ifdef _MSC_VER
#   define strtok_r strtok_s
#endif

void split_in_two(const char* input)
{
    // we first make a copy of the input. We don't have to,
    // but strtok_r operates by overwriting the delimiter in the
    // input string, and I want to keep it clean.
    // you can remove that step if you're okay with trashing
    // the original.
    char* source = malloc(strlen(input) + 1);
    if (!source)
        abort();
    strcpy(source, input);

    char left[50], right[50];
    rsize_t length;
    char* cursor;

    // get the first one.
    // note, strtok_r replaces the delimiter '|' in the string with a '\0',
    // so strcpy will stop at the right spot.
    strcpy(left, strtok_r(source, "|", &cursor));

    // at this point, cursor will point to the start to the second part,
    // or NULL if there's nothing left
    if (!cursor)
        return;

    // note, we call it with NULL when we're still processing the same string
    // giving it a non-null input resets it
    strcpy(right, strtok_r(NULL, "|", &cursor));

    printf(
        "Left: %s\n"
        "Right: %s\n",
        left, right
    );

    free(source);
}

int main(void)
{
    split_in_two("Hello|World");
}