%%s 3/3/96
%%d D 1.2 29-Jul-82 07:50:21 j 2 1
%%c Modified tail.w`tail.r`defns to double the size of the line buffer
%%c (from 3000 to 6000) to handle a larger number of lines.
%%s 0/0/0
%%d D 1.1 25-Mar-82 12:15:23 v1.1 1 0
%%c Version 1.1 is the Spring 1982 Distribution of the LBL/Hughes release
%%c of the Software Tools Virtual Operating System software and documentation.
%%T
%%I 1
%%D 2
#-h- tail.r          2051  asc  25-mar-82 08:55:42  v1.1 (sw-tools v1.1)
#-h- defns            160  asc  25-mar-82 08:55:18  v1.1 (sw-tools v1.1)
%%E 2
%%I 2
#-h- tail.r          2044  asc  29-jul-82 07:22:55  j (sventek j)
#-h- defns            160  asc  29-jul-82 07:18:25  j (sventek j)
%%E 2
 #   include standard symbol definitions
 #        include ratdef
 
%%D 2
define(MAXBUF,3000)     # line buffer size
%%E 2
%%I 2
define(MAXBUF,6000)     # line buffer size
%%E 2
define(DEFAULT,23)      # default if no argument
#-h- main             971  asc  25-mar-82 08:55:19  v1.1 (sw-tools v1.1)
# tail - print tail portion of a file
 DRIVER(tail)
   character arg(MAXLINE)
   integer n, i, fd
   integer ctoi, getarg, open

   call query("usage:  tail [-n] [file] ...")
   n = DEFAULT
   fd = ERR
   for (i=1; getarg(i, arg, MAXLINE) != EOF; i=i+1)
        {
        if (arg(1) == '-' & arg(2) != EOS)
                {
                j = 2
                n = ctoi(arg, j)
                if (n <= 0)
                        call error ("invalid size.")
                }
        else if (arg(1) == '-' & arg(2) == EOS)
                {
                fd = STDIN
                call ptail (n, fd)
                }
        else
                {
                fd = open(arg, READ)
                if (fd == ERR)
                        call cant(arg)
                call ptail (n, fd)
                call close(fd)
                }
        }
 
   if (fd == ERR)               #no files specified, read STDIN
        call ptail (n, STDIN)
   DRETURN
   end
#-h- ptail            701  asc  25-mar-82 08:55:21  v1.1 (sw-tools v1.1)
 ## ptail - print last 'n' lines of file 'fd'
 subroutine ptail (nlins, fd)
 integer n, fd, nlins
 character buf(MAXBUF)
 character getch
 integer head, tail, i
 
   head = 1
   tail = 1
   n = nlins
   while (getch(buf(tail), fd) != EOF) {
      tail = mod(tail, MAXBUF) + 1
      if (tail == head)
         head = mod(head, MAXBUF) + 1
      }
   for (i = tail; i != head; ) {
      i = i - 1
      if (i == 0)
         i = MAXBUF
      if (buf(i) == '@n') {
         n = n - 1
         if (n < 0) {
            i = mod(i, MAXBUF) + 1
            break
            }
         }
      }
   for (head = i; head != tail; head = mod(head, MAXBUF) + 1)
      call putch(buf(head), STDOUT)
 
 return
 end
#-h- tail.fmt         641  asc  25-mar-82 08:55:44  v1.1 (sw-tools v1.1)
.so ~bin/manhdr
.hd Tail (1) 26-Aug-79
print last lines of a file
.sy
tail [-n] [file] ...
.ds
Tail prints the last "n" lines of the indicated file.
If 'n' is omitted, the last 23 lines are printed.
 
If "file" is omitted or is "-", tail reads the standard input.
.sa
split
.au
David Hanson and friends (U. of Arizona)
.bu
An internal buffer of MAXBUF characters is kept.
If the value of "n" would require buffering more characters than
the buffer can hold, tail prints the last MAXBUF characters of the file.
In this case, the first line of output may not be an entire line.
MAXBUF is a definition in the source code which may be adjusted.
%%E 1