Initializing help system before first use

fselect

Purpose
Select the active input, output or error stream.
Synopsis
procedure fselect(stream:integer)
Argument
stream 
The stream number
Example
The following saves the file ID of the default output before switching output to the file mylog.txt. Subsequently, the file ID of the current output stream is saved and the default output is again selected. 
def_out:= getfid(F_OUTPUT)
fopen("mylog.txt", F_OUTPUT)
  ...
my_out:= getfid(F_OUTPUT)
fselect(def_out)
Further information
1. This procedure selects the given stream as the active input, output or error stream. The concerned stream is designated by the opening status of the given stream (that is, if the given stream has been opened for reading, it will be assigned to the default input stream). The stream number can be obtained with the function getfid.
2. The default input, output and error streams have respectively numbers 0, 1 and 2.
3. An IO error will be raised if the requested file ID does not exist.
Related topics
fclose, fopen, getfid, fwrite, fwriteln.

Parent Topic Predefined functions and procedures

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