VMS Help RTL Routines, STR$, STR$TRIM, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 destination-string

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor

    Destination string into which STR$TRIM copies the trimmed string.
    The destination-string argument is the address of a descriptor
    pointing to the destination string.

 source-string

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor

    Source string which STR$TRIM trims and then copies into the
    destination string. The source-string argument is the address
    of a descriptor pointing to the source string.

 resultant-length

    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       write only
    mechanism:    by reference

    Number of bytes that STR$TRIM writes into destination-string,
    not counting padding in the case of a fixed-length string. The
    resultant-length argument is the address of an unsigned word
    into which STR$TRIM writes the length of the output string.
    If the input string is truncated to the size specified in the
    destination-string  description, resultant-length is set to
    this size. Therefore, resultant-length can always be used by
    the calling program to access a valid substring of destination-
    string.