string validation for int and long (strisint, strislong)

From: jake1138 (cooljake_at_gmail.com)
Date: 02/25/05 

Date: 24 Feb 2005 15:53:10 -0800

Maybe this is a newbie thing and everyone already knows how to do this,
but I figured I'd post these functions anyway in case someone finds
them useful. I used Jack Klein's example (see link below) and made
functions out of it.

http://home.att.net/~jackklein/c/code/strtol.html

Here are functions that will validate a string to see if it represents
an integer or long, respectively:

/*
 * checks to see if string is an integer
 *
 * returns 1 if true, 0 if false
 */
int strisint(const char *str, size_t size)
{
    char *endptr;
    long longint;

    errno = 0;
    longint = strtol(str, &endptr, 10);
    if (errno == ERANGE || longint < INT_MIN || longint > INT_MAX
        || endptr == str || *endptr != '\0') {
        return 0;
    } else {
        return 1;
    }
}

/*
 * checks to see if string is a long integer
 *
 * returns 1 if true, 0 if false
 */
int strislong(const char *str, size_t size)
{
    char *endptr;
    long longint;

    errno = 0;
    longint = strtol(str, &endptr, 10);
    if (errno == ERANGE || endptr == str || *endptr != '\0') {
        return 0;
    } else {
        return 1;
    }
}

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