7. redir

DOS, in its many flavors and versions, lacks a decent I/O redirection mechanism. Sure, it's got < and > and >>, but what about error messages? Lots of people ask, "How do you send those error messages to a file?" Well, you use a program like redir.

redir is basically a program that manipulates the standard file descriptors by copying them, closing and opening them, etc. Once it has the file descriptors where it wants them, it runs your program, which inherits the changed descriptors. Thus, redir has nearly complete control over the input and output of your program.

It also allows you to view the exit code of the program, and the elapsed time of the program, by supplying the appropriate options on the command line.

Note that redir is built with command-line expansion and response files disabled, so as to allow the application to control that themselves. This means that you can't use those features to provide redir's options or the command name, but if you use them for the command's options, the command will do the expansion if it wants to.

The exit code of redir is 1 if it exits on its own accord, else it returns the same error code as the program it runs.

Usage: redir [-i file] [-o file] [-oa file] [-e file] [-ea file] [-eo] [-oe] [-x] [-t] command [args . . .]

-i file

Redirect standard input from file

-o file

Redirect standard output to file

-oa file

Append standard output to file

-e file

Redirect standard error to file

-ea file

Append standard error to file

-eo

Redirect standard error to standard output

-oe

Redirect standard output to standard error

-x

Print the exit code of the command after it exits. If the exit code is 0..255, it is printed as is. If it is not, the low byte (0..255) is printed in decimal and the whole value is also printed in hex.

-t

Print elapsed time, either in seconds (for short runs) or hours:minutes:seconds.

Options are processed in the order they are encountered. Thus, "-o foo -eo" means "redirect output to foo, then redirect errors there also", whereas "-eo -o foo" means "send errors to where output was going, then move output to foo".

Examples:

To redirect errors to a file:

redir -e errors.lst command ...

To redirect output to a file, and errors through a pipe:

redir -eo -o prog.out command ... | pipe