difficult starting cmd prompt with execution of two commands

[taripo]

I am having difficulty starting cmd prompt with execution of two commands



this works fine (though is just for one command)

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C:\>start cmd /k echo abc

but this, with two commands, fails.. it closes immediately.

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C:\>start cmd /k (echo abc & echo def)

I tried adding a pause to get a better grasp of what was happening, but then I got another error

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C:\>start cmd /k (echo abc & echo def & pause)
def
'pause)' is not recognized as an internal or external command,operable program or batch file.

C:\>start cmd /k ((echo abc) & (echo def) & (pause))
) was unexpected at this time.

C:\>

So I can't really see what's going on and how to do it

[elzooilogico]

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start "" cmd /k "bla & bla & bla"

or

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start "" cmd "/k "bla &bla & bla""

cyquotation makes quite a difference. first quotes are window title

[sst]

You know that & is command splitter but forgot that this line

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start cmd /k (echo abc & echo def)

will be parsed and splitted in to two separate commands before the second cmd instance have a chance to grab it as command line.
your line will basically will be converted to this before execution

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start cmd /k (echo abc
echo def)

The first line starts a new instance of cmd passing (echo abc as the command to execute but it's syntax is invalid because of the unbalanced parentheses, the new cmd instance will not complain about it but it will be terminated immediately then the second line echo def) will be executed which will output def)

For this to work you have two options:
1. Put the the part that is intended to be passed to the second cmd instance in quotes

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start cmd /k "(echo abc & echo def)"

2. Or escape the special characters to prevent them to be parsed by parent cmd

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start cmd /k ^(echo abc ^& echo def^)

But in your particular test case there is no need to use parentheses at all so it can be simplified like this

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start cmd /k "echo abc & echo def"
start cmd /k echo abc ^& echo def

[taripo]

@sst, thanks, you're spot on, I hadn't realised that the round brackets / parentheses , when occurring in a parameter, don't group things! (is that right?)
You solved it though. I like both those solutions, the quotes one, and the escaping the ampersand one.

you explained that very well with how the parameters are broken down.. I tested it and indeed

(w.c and w2.c referenced at bottom of post)

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C:\>w cmd /k echo abc & echo def
argv[0] = w
argv[1] = cmd
argv[2] = /k
argv[3] = echo
argv[4] = abc
def

C:\>w cmd /k echo (abc & echo def)
argv[0] = w
argv[1] = cmd
argv[2] = /k
argv[3] = echo
argv[4] = (abc
def)

C:\>

C:\>w cmd /k echo abc ^& echo def
argv[0] = w
argv[1] = cmd
argv[2] = /k
argv[3] = echo
argv[4] = abc
argv[5] = &
argv[6] = echo
argv[7] = def

So I see the importance of the quotes there.. or the escaping the ampersand

Funnily enough this doesn't work

C:\>start cmd /k echo abc "&" echo def

even though the argsv come out the same

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C:\>w cmd /k echo abc "&" echo def
argv[0] = w
argv[1] = cmd
argv[2] = /k
argv[3] = echo
argv[4] = abc
argv[5] = &
argv[6] = echo
argv[7] = def

Though the command line is different for them,

C:\>w2 start cmd /k echo abc "&" echo def
w2 start cmd /k echo abc "&" echo def

C:\>w2 start cmd /k echo abc ^& echo def
w2 start cmd /k echo abc & echo def
C:\>



so maybe start uses some kind of mixture of first getting the command line then splitting into arguments

@elz , well spotted re quotes around the echo, though I think the start "" is a bit of a red herring here.. it's not necessary. It is necessary when the path to the executable contains a space. e.g. C:\>start c:\crp\zzzza.bat works, but C:\>start "c:\crp\bab zab\fafa.bat" fails and requires C:\>start "" "c:\crp\bab zab\fafa.bat" So there are cases when you need the "" but not here.

@sst could solution and explanation.

Thanks guys

* w.c and w2.c https://pastebin.com/raw/KTWihmPB

[sst]

Funnily enough this doesn't work

C:\>start cmd /k echo abc "&" echo def

even though the argsv come out the same

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C:\>w cmd /k echo abc "&" echo def
argv[0] = w
argv[1] = cmd
argv[2] = /k
argv[3] = echo
argv[4] = abc
argv[5] = &
argv[6] = echo
argv[7] = def

Though the command line is different for them,

C:\>w2 start cmd /k echo abc "&" echo def
w2 start cmd /k echo abc "&" echo def

C:\>w2 start cmd /k echo abc ^& echo def
w2 start cmd /k echo abc & echo def
C:\>

so maybe start uses some kind of mixture of first getting the command line then splitting into arguments

start does not touch command line of the target command and will pass it as is.

That is the effect of C-Runtime's command line processor in your w program which will split it in to separate argv elements and unquotes each of them, cmd on the other hand, accesses raw command line and uses it's own parser for processing it rather than using argv.

And everything that comes after /K or /C will be parsed and processed as if it was typed at cmd's command prompt. Except when certain conditions are met, cmd will always unquote this part first then continues with rest of the processing. (To see when and how cmd will keep quotes after /K or /C refer to cmd /?)

So with the following:

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C:\>start cmd /k echo abc "&" echo def

the second cmd will see this as the command to execute:

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echo abc "&" echo def

which will output:

abc "&" echo def

And with this:

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C:\>start cmd /k "echo abc & echo def"

The second cmd will see this as the command to execute:

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"echo abc & echo def"

Unquotes it:

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echo abc & echo def

Then executes which will output:

abc
def