In the various operating systems, the window running ivi can be resized using the mouse buttons. Instead you must use the CDirectory command. This changes the working directory in the subshell, but it reverts to the former value when the shell is closed, and thus has no effect. UN ls >tmp - write the current directory to file tmp, whence it can be FEtched to the corefile.īut not UN cd fred (change the current directory to fred). (This, incidentally, is how the command DIrectory is implemented.) For most users, the distinction will be irrelevant. The shell re-entered by is still in the working directory from which ivi was called. If, for example, the file directory has been changed within ivi, the UN shell will be in the new directory. re-enters the shell from which ivi was called UN enters a subshell of ivi, which inherits some of ivi's environment. Superficially, this appears to be same as UN with no parameter, but there is a subtle difference. The shell command:Įarlier we described the Suspend key, which suspends ivi, putting it into the "background" and re-entering a UNIX shell. If is omitted, an interactive shell is spawned, and the user can enter commands at the keyboard. The system then prompts for a to get you back to ivi. The screen is cleared, the command is carried out, and its output (if any) is written to the screen. If the parameter is present, this is the command to be executed within the shell.
Parameter: The two commands are the same. Purpose: Spawn a shell and execute a UNIX (or DOS) command within it Note that, unlike the ivi operation keys, these keys are set up at entry to ivi, and cannot be changed or disabled by the user. In some instances, the Abort key may leave the display in an incorrect state or the text cursor in the wrong place. Current computers, however, are fast enough that this problem rarely seems to arise. (An aborted SOrt, for instance, retains all the lines of the original, but these are only partially sorted an aborted FEtch correctly fetches part of the file.) A user who doesn't want to wait for a long operation to be completed can therefore terminate it using the Abort key. These operations have been written to terminate quickly but gracefully if the abort flag becomes set. In days gone by, certain activities, such as FEtching or SOrting a very large file, could take many minutes to complete. (c) is another feature which may have outlived its usefulness. Clearing the function-stack causes the offending function or procedure to terminate. (b) caters for the possibility that an ivi function or procedure has entered an endless loop. (a) corrects this by discarding queued operations. In the Miscellanea webpage, we have noted the annoying phenomenon of excessive type-ahead, where many repeated operations may be queued if the time taken complete an operation far exceeds the repetition time of the keys.
The Abort key allows ivi to recover from several damaging activities. Restores ivi back to the foreground, and regenerates the display. In a windowing system, the user can simply open another window instead. This allows a user to suspend the editor to carry out some other activity. It puts ivi into the background, and returns the user to the shell from which ivi was called. The Suspend key is a hangover from earlier times. If ivi is under keyboard control, the keys apply directly to ivi.
#IVI SYSTEM DRIVER#
If ivi is running under the control of a "driver program", these keys affect the driver program, suspending or killing it, and returning control to the keyboard. is the Suspend key (or perhaps, depending on your keyboard) is the Abort key. Two keys generate signals which trigger special actions within ivi. Ivi System Stuff ivi System Stuff Suspending, Aborting, Shelling Out and Resizing
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