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Is it possible to set an environment variable on the bash command line?

I am trying to set an environment variable for Bash. However, I need this to be set before any shell startup script (including /etc/profile

), because it /etc/profile

acts differently depending on the value of this variable.

Specifically, I want to create a shortcut for MinTTy that works like git-bash

, but I need to set an environment variable MSYSTEM

before the shell starts, or at least before it starts processing any startup scripts.

A decision will also be made in which MinTTy sets an environment variable before it starts the shell.

Edit: What I'm really looking for is a command line option for BASH that will set an environment variable somewhat similar to the option -D

on most C (and others) compilers. This will be the "general case". Alternatively, a similar option (command line or config) for MinTTy will do the job as well.

For my specific need, I have an idea for a potential job: run a BASH script - no startup scripts - that sets my required variable and exec

another shell as the login shell.

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3 answers


Define the purpose of your shortcut file as follows:

C:\cygwin64\bin\mintty.exe /bin/bash -l -c "MSYSTEM=MINGW64 exec -l bash"

This command:

  • calls bash

    directly as login shell ( -l

    )
  • passes it the command ( -c

    ), which defines the environment variable of interest ( MSYSTEM=MINGW64

    ), and then calls a new copy bash

    ( exec -l bash

    ), which inherits the existing environment, plus the new definition, but returns the profile again due to -l


    (and appends -

    to the executable name given in $0

    ( -bash

    ), as it happened if you started Mintty with just -

    , which is what the regular Cygwin64 Terminal

    shortcut does ).


An alternative is to set the environment variable on Windows first.

  • [Not an option for the OP] If the environment variable should always have the same value, set it aggressively like this: run sysdm.cpl

    , go to tab Advanced

    , click Environment Variables...

    and define the variable MSYSTEM

    as needed.

  • To define an ad-hoc variable, create a batch file as follows and make a shortcut target for the batch file:

    @echo off

# Define the env. variable with the desired value.
set "MSYSTEM=MINGW64"

# Invoke Mintty with a login shell, which will now see the env. variable.
# Adjust the path to mintty.exe as needed.
c:\cygwin64\bin\mintty.exe -

Note. Opening a batch file from a shortcut briefly opens a regular console window before opening Mintty, which may not be desirable.

A simple WSH script helper as shown in this answer can prevent this.

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While I have already accepted the answer above, I found this link which specifically addresses the second part of my question (Mintty specific) or an alternative way to set an environment variable before running the command.

The contents of a Windows shortcut can be:



C:\cygwin64\bin\mintty.exe -t "Title" /bin/env "MSYSTEM=MINGW64" /bin/bash -l

(Suggested Mintty Tips : Setting Environment Variables .)

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You just have to do the same as on the command line. Therefore, you can:

set VAR=VarContents
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