i was unexpected at this time about grunt-shell

[sindresorhus]

Node internally uses cmd on Windows, not bash. You would have to do bash -c "cd i18n..." to force use of bash.

[shivapoudel]

@sindresorhus Thanks for the solution.....

[shivapoudel]

Node internally uses cmd on Windows, not bash. You would have to do bash -c "cd i18n..." to force use of bash. After some tweaks by adding bash -c and it works in Windows 8.1 cmd.

    // Run Grunt Shell tasks.
    shell: {
        options: {
            stdout: true,
            stderr: true
        },
        txpull: {
            command: [
                'cd i18n',
                'tx pull -a -f'
            ].join( '&&' )
        },
        potomo: {
            command: [
                'cd i18n/languages',
                'bash -c "for file in *.po ; do msgfmt $file -o ${file%%.*}.mo ; done"'
            ].join( '&&' )
        }
    },