How can I pass arguments to a batch file?

Question

I need to pass an ID and a password to a batch file at the time of running rather than hardcoding them into the file.

Here\'s what the command line looks like:

Answer 1

Inspired by an answer elsewhere by @Jon, I have crafted a more general algorithm for extracting named parameters, optional values, and switches.

Let us say that we want to implement a utility foobar. It requires an initial command. It has an optional parameter --foo which takes an optional value (which cannot be another parameter, of course); if the value is missing it defaults to default. It also has an optional parameter --bar which takes a required value. Lastly it can take a flag --baz with no value allowed. Oh, and these parameters can come in any order.

In other words, it looks like this:

foobar  [--foo []] [--bar ] [--baz]

Here is a solution:

@ECHO OFF
SETLOCAL
REM FooBar parameter demo
REM By Garret Wilson

SET CMD=%~1

IF "%CMD%" == "" (
  GOTO usage
)
SET FOO=
SET DEFAULT_FOO=default
SET BAR=
SET BAZ=

SHIFT
:args
SET PARAM=%~1
SET ARG=%~2
IF "%PARAM%" == "--foo" (
  SHIFT
  IF NOT "%ARG%" == "" (
    IF NOT "%ARG:~0,2%" == "--" (
      SET FOO=%ARG%
      SHIFT
    ) ELSE (
      SET FOO=%DEFAULT_FOO%
    )
  ) ELSE (
    SET FOO=%DEFAULT_FOO%
  )
) ELSE IF "%PARAM%" == "--bar" (
  SHIFT
  IF NOT "%ARG%" == "" (
    SET BAR=%ARG%
    SHIFT
  ) ELSE (
    ECHO Missing bar value. 1>&2
    ECHO:
    GOTO usage
  )
) ELSE IF "%PARAM%" == "--baz" (
  SHIFT
  SET BAZ=true
) ELSE IF "%PARAM%" == "" (
  GOTO endargs
) ELSE (
  ECHO Unrecognized option %1. 1>&2
  ECHO:
  GOTO usage
)
GOTO args
:endargs

ECHO Command: %CMD%
IF NOT "%FOO%" == "" (
  ECHO Foo: %FOO%
)
IF NOT "%BAR%" == "" (
  ECHO Bar: %BAR%
)
IF "%BAZ%" == "true" (
  ECHO Baz
)

REM TODO do something with FOO, BAR, and/or BAZ
GOTO :eof

:usage
ECHO FooBar
ECHO Usage: foobar ^ [--foo [^]] [--bar ^] [--baz]
EXIT /B 1

• Use SETLOCAL so that the variables don't escape into the calling environment.
• Don't forget to initialize the variables SET FOO=, etc. in case someone defined them in the calling environment.
• Use %~1 to remove quotes.
• Use IF "%ARG%" == "" and not IF [%ARG%] == [] because [ and ] don't play will at all with values ending in a space.
• Even if you SHIFT inside an IF block, the current args such as %~1 don't get updated because they are determined when the IF is parsed. You could use %~1 and %~2 inside the IF block, but it would be confusing because you had a SHIFT. You could put the SHIFT at the end of the block for clarity, but that might get lost and/or confuse people as well. So "capturing" %~1 and %~1 outside the block seems best.
• You don't want to use a parameter in place of another parameter's optional value, so you have to check IF NOT "%ARG:~0,2%" == "--".
• Be careful only to SHIFT when you use one of the parameters.
• The duplicate code SET FOO=%DEFAULT_FOO% is regrettable, but the alternative would be to add an IF "%FOO%" == "" SET FOO=%DEFAULT_FOO% outside the IF NOT "%ARG%" == "" block. However because this is still inside the IF "%PARAM%" == "--foo" block, the %FOO% value would have been evaluated and set before you ever entered the block, so you would never detect that both the --foo parameter was present and also that the %FOO% value was missing.
• Note that ECHO Missing bar value. 1>&2 sends the error message to stderr.
• Want a blank line in a Windows batch file? You gotta use ECHO: or one of the variations.