[sic strtol(3)] Convert a string value to a long long

parse_long_long.c

#include <stdlib.h>
#include <limits.h>
#include <errno.h>

/**
 * [sic strtoll(3)] Convert a string value to a long long
 *
 * @str     the value string
 * @delim   delimiter character(an invalid one) for a success match
 *          note '\0' for a strict match
 *          other value indicate a substring conversion
 * @base    numeric base
 * @val     where to store parsed long value
 * @return  1 if parsed successfully  0 o.w.
 *
 * @see:    https://stackoverflow.com/a/14176593/10725426
 */
int parse_long_long(const char *str, char delim, int base, long long *val)
{
    int ok;
    char *p;
    long long t;

    errno = 0;
    t = strtoll(str, &p, base);

    ok = errno == 0 && *p == delim;
    if (ok) *val = t;

    return ok;
}

/**
 * [sic strtoll(3)] Convert a string value to a long
 * @see: parse_long_long()
 */
int parse_long(const char *str, char delim, int base, long *val)
{
    long long t;
    int ok;

    ok = parse_long_long(str, delim, base, &t) &&
            (t & ~((unsigned long long) ULONG_MAX)) == 0;
    if (ok) *val = t;

    return ok;
}

NOTE: You can rename parse_long_long to parse_llong