This is a collection of Windows batch scripts to implement a queue (FIFO) of commands, where each command is designed to be run in sequence.
It uses a single file system directory as the backing store for the command queue.
The commands that can be put in the queue are themselves Windows batch scripts
with the .cmd extension. The queue processor simply runs one command after
another, in their date order.
Once a command has been executed successfully, it is renamed by appending
.bak to its name. For example, foobar.cmd will become foobar.cmd.bak.
Any output from the command will be saved to a log file bearing the same name
as the command but with .log appended. For example, the log for foo.cmd
will be named foo.cmd.log.
The queue processor scripts is called cmdqp.cmd. Most sub-commands of the
queue processor take --qdir <DIR> option where <DIR> specifies the queue
directory. If omitted, the queue directory is assumed to be cmdqp.q that is
a sub-directory of where cmdqp.cmd resides.
If a single command fails, the queue processor stops all further processing
and exits. A file named lasterror.log is placed in the queue directory that
can be used for troubleshooting the last failed command.
The command lines shown in this document assume Windows Command Prompt is
your shell and begin with call followed by the batch file name.
For simplcity and brevity, the extension is omitted as the shell does not
require it (inferring it from the PATHEXT environment variable). The call
portion can also be omitted if you do not care about the exit code to
distinguish between a successful and a failed execution.
To queue a command safely, use qcmd.cmd as follows:
call qcmd <QDIR> <CMDPATH>
where <QDIR> is queue directory and <CMDPATH> is the batch script to
queue. <CMDPATH> will be atomatically copied to <QDIR>.
The file names of commands (batch files) in the queue must be unique. It is
the responsibility of the caller of qcmd.cmd to ensure that the file name
part in <CMDPATH> is unique among others in QDIR. Appending a randomly
generated GUID to the file name is one way to guarantee uniqueness. If not,
the queue processor will exit with a failure.
Running:
call cmdqp help
shows a summary of sub-commands along with their descriptions:
Runs command scripts in sequence on a FIFO basis.
Usage:
cmdqp help displays this help
cmdqp run run queued tasks once
cmdqp daemon run queued tasks forever
cmdqp list list the command files of the queue
cmdqp logs list the logs
cmdqp pause pause before next task (until unpaused)
cmdqp unpause unpause
cmdqp halt finish current task (if any) then stop
To run all the commands in the queue and exit, run:
call cmdqp run
To run all the commands in the queue, including any future commands that may be queued, use the daemon mode:
call cmdqp daemon
It will run the queue processor in a new and detached shell. To run in the
same session, use the run command with the --forever flag:
call cmdqp run --forever
To list all command currently queued for execution, run:
call cmdqp list
To see the list of log files of executed commands, run:
call cmdqp logs
To halt the queue processor after it has finished running the current command in the queue (if it is the case), run:
call cmdqp halt
This command is useful to gracefully stop the queue processor if, for example, it was started in the daemon mode.
To temporarily pause the execution of commands in the queue without halting the queue processor, run:
call cmdqp pause
The pause remain in effect until you run:
call cmdqp unpause