strncat

   NAME
    strncat  - concactenate a string to an existing string up to a
           maximum number of characters

   SYNOPSIS
    char *d = strncat(d, s, n);
    char *d;
    const char *s;
    int n;

   FUNCTION
    scans the destination buffer for the nul terminator and then
    appends the source string to the destination buffer (removing
    the nul terminator and placing one at the end after the
    concactenation).  However, only up to n characters is concactenated
    including the nul.  If the source string is exactly n characters
    long no nul will be appended.  If the source string is longer
    than n characters then only the first n characters of the source
    string will be appended (and no nul will be).

    A pointer to the beginning of the destination buffer is returned.

   EXAMPLE
    #include <stdio.h>
    #include <string.h>
    #include <assert.h>

    main()
    {
        char d[32];
        char *s1 = "fu";
        char *s2 = "bar";
        char *p;

        d[2] = 23;
        d[5] = 24;
        d[6] = 25;
        strcpy(d, s1);          /*  overwrites d[2] with a nul  */
        assert(d[2] == 0);

        p = strncat(d, s2, 3);  /*  does NOT overwrite d[5] with a nul */
        assert(d[5] == 24);
        assert(p == d);

        strcpy(d, s1);
        p = strncat(d, s2, 20); /*  does        */
        assert(p == d);
        assert(d[5] == 0);
        assert(d[6] == 25);     /*  stops at the nul, so d[6] was not modified */

        puts(d);                /*  fubar   */

        return(0);
    }

   INPUTS
    char *d;    pointer to destination buffer which already contains
            a string (which could be just a 0).

    char *s;    pointer to the nul terminated source string

    int n;      maximum number of characters to concactenate

   RESULTS
    char *d;    same as the first argument, a pointer to destination buffer.

   SEE ALSO
    strncpy, strcpy, strcat