**CIGAL Reference Manual, Chapter 1 (Topics): redirect**
===== Redirect -- Redirecting Printed Output =====
CIGAL generates text output in several different output "channels" each of which can be controlled independently.  Any one of the channels can be assigned to the special devices, TERMINAL or PRINTER, or to a disk file. Sending output to TERMINAL means it gets printed on the standard computer screen, whereas sending to PRINTER causes the output to be sent over the parallel printer port.  CIGAL's standard channels are:

    Channel     Default Device      Description
    =======     ==============      ===========
    OUTPUT      TERMINAL            All normal output
    ERROR       TERMINAL            Error messages
    JOURNAL     inactive            A record of every interactive command
                                     (see \L[JOURNAL][2])
    LOG         inactive            A copy of all OUTPUT messages sent to the
                                    terminal; LOG cannot go to the terminal
    DEBUG       TERMINAL            Debugging messages (see \L[DEBUG][4])

You use the OPEN and CLOSE commands to assign a channel to a different
device or to a disk file.  After assigning a channel with OPEN it remains
assigned until it is reassigned or closed (see [[jvs:cigal:manual:chapter2:open|OPEN(2)]] and [[biac:jvs:cigal:manual:chapter2:close|CLOSE(2)]]).

CIGAL also recognizes the UNIX (and DOS) convention for redirecting the
output of any individual command simply by adding '> target' to the end of
the command line.  The syntax is:

          command_line >  filename        ; write output to FILENAME
    or:   command_line >> filename        ; append output to FILENAME
    or:   command_line >  printer         ; send output to printer
    or:   command_line >  terminal        ; send output to screen
    or:   command_line >  stringvarb      ; send output to string variable

where COMMAND_LINE is any CIGAL command, EXCEPT an arithmetic expression.
Note: If the command line begins with a function, variable, or number, then
CIGAL thinks it is an arithmetic expression and will interpret the > or >> as
arithmetic operators.  To get around this, you should use the TYPE command
(see [[jvs:cigal:manual:chapter1:syntax|SYNTAX(1)]] and [[biac:jvs:cigal:manual:chapter2:type|TYPE(2)]]).

Note: the > or >> is treated as a separate argument by the parser and
therefore MUST have blank spaces before and after it (see [[jvs:cigal:manual:chapter1:syntax|SYNTAX(1)]]).

For example,
      open journal 'logfile'            ; these first 2 lines send a copy of
      open log 'logfile'                ; everything you type, and all
                                        ; messages printed on the screen
                                        ; to LOGFILE.
      type random(30)                   ; print 30 numbers on the screen
      type random(30) > ran.dat         ; create disk file named RAN.DAT
                                        ; and print the 30 numbers there
      type vga0(0:11,0:20) >> ran.dat   ; add values in VGA0 to RAN.DAT
      open output 'junk'                ; now assign OUTPUT to file JUNK
      type 'Area=' 3.14*R*R             ; this goes to file JUNK
      type 'Area=' 3.14*R*R > terminal  ; this is printed on the screen
      list 'ran.dat' > printer          ; print file RAN.DAT on printer
      type vdata                        ; print VDATA values in file JUNK
      vecs                              ; print VECS values in file JUNK
      close output                      ; close the file assigned to OUTPUT

When you close a file or channel using the CLOSE command, the associated channel returns to its default output device.  However, when you redirect output using > or >>, after the command has finished the standard output channel, the function returns to whatever it was assigned to previously (see the last TYPE example above).

If you use > or >> to redirect the output of a macro program, then all
standard output produced by that macro will be redirected.  Thus,
                mymacro > mac.dat
is approximately equivalent to
                open output mac.dat
                mymacro
                close mac.dat

See [[jvs:cigal:manual:chapter1:files|FILES(1)]] for more information on CIGAL's usage of disk files.


**See Also:**\\
[[jvs:cigal|CIGAL Home]], 
[[jvs:cigal:manual|CIGAL Manual]], 
[[jvs:cigal:manual:chapter1|Topics List]], 
[[jvs:cigal:manual:help|Manual Help]]