NAME
    files - return a file or the maximum number of open files

SYNOPSIS
    files([fnum])

TYPES
    fnum	int

    return	files, int or null

DESCRIPTION
    This function, then given the argument fnum, will use it as an
    index into an internal table of open file and return a file value.
    If that entry in the table is not in use, then the null value is
    returned instead.  When no args are given, the maximum number of
    open files is returned.

    If you overwrite a variable containing a file value or don't save the
    result of an 'fopen', the opened file still remains open.  Such 'lost'
    files can be recovered by using the 'files' function.

    The first 3 file entries always refer to standard input, output
    and error respectively.  (see the example below)  These three
    files are already open by the calculator and cannot be closed.

    When calc starts up, it scans for open file descriptors above
    stderr (2) and below MAXFILES (20).  Any open descriptor found
    is assumed to be an open file opened in an unknown mode.  Calc
    will try to read and write to this file when directed.

    Consider the following commands:

	$ echo "A line of text in the file on descriptor 5" > datafile
	$ calc 5<datafile

    then one could do the following:

	> files(5)
		FILE 5 "descriptor[5]" (unknown_mode, pos 0)
	> fgetline(files(5))
		"A line of text in the file on descriptor 5"

EXAMPLE
    > fd = fopen("/etc/motd", "r")
    > fd
	    FILE 3 "/etc/motd" (reading, pos 0)
    > files(3)
	    FILE 3 "/etc/motd" (reading, pos 0)

    > if (isnull(files(4))) print "not open"
    not open

    > stdin = files(0)
    > stdout = files(1)
    > stderr = files(2)

    > print files()
    20

LIMITS
    none

LIBRARY
    none

SEE ALSO
    errno, fclose, feof, ferror, fflush, fgetc, fgetline, fgets, files, fopen,
    fprintf, fputc, fputs, fseek, fsize, ftell, isfile, printf, prompt