In my application, users can store a command to be run at a certain point. Right now, someone added "C:\Program Files\Internet Explorer\iexplore.exe http://www.google.com". This is invoked by using the WinExec function. Now, when this command is changed to "start http://www.google.com", the function returns an ERROR_FILE_NOT_FOUND, while it seems this should work from examples I find online.
WinExec is for starting processes. But what you are trying to do is best done by asking the shell to work out which program is associated with http:// and display the URL with that. What you need to do is call ShellExecute or ShellExecuteEx.
For example:
ShellExecute(0, NULL, "http://www.google.com", NULL, NULL, SW_SHOWDEFAULT);
The reason that start does not work with WinExec is that start is not an executable. It's a built in command handled by the interpreter, cmd.exe. So you could use WinExec if you passed cmd.exe (or the value of the COMSPEC environment variable) and got cmd.exe to call start. But that's the wrong way to do it.
The command should be:
cmd.exe /c start http://www.google.com
and you shoudn't use WinExec, read the note:
Note This function is provided only for compatibility with 16-bit
Windows. Applications should use the CreateProcess function.
if you use WinExec for opening URLs, use ShellExecute by passing open to lpOperation insted:
ShellExecute(NULL,
TEXT("open"),
TEXT("http://www.google.com"),
NULL,
NULL,
SW_SHOWNORMAL);
The URL will be opened in the user default browser.
Related
Suppose I'm working in a system that wants to execute something in a workflow step, but I want it to do nothing instead.
Unlike the slightly-related question Dummy command in windows cmd, I'm not in any sort of shell (that I'm aware of). I can only point to an executable and provide parameters.
Is there anything in a typical Windows installation that can be executed as a do-nothing placeholder and returns 0 as its exit code?
I could install a dummy script, but I'd rather avoid doing that to maintain some portability.
C:\Windows\System32\cmd.exe /D /C ""
If there's no shell, then %SYSTEMROOT% is likely not available. For a typical, out-of-the-box installation, the above path is expected. Otherwise, customize to fit your environment.
From the help text:
/C Carries out the command specified by string and then terminates
. . .
/D Disable execution of AutoRun commands from registry (see below)
Following up /C with "" executes nothing. Invoking /D prevents any default scripts from running.
Finally, this returns 0, so it won't interrupt the workflow.
In a Windows batch file, or in the Command Prompt, what's the difference between calling start mspaint, for example, and mspaint? They appear to do exactly the same thing.
Another example, where all 4 cases appear to do the same thing. Can you please help me understand what are the subtle differences, if any?
taskmgr
C:\Windows\System32\Taskmgr.exe
start taskmgr
start C:\Windows\System32\Taskmgr.exe
Follow-up: it looks like start opens a separate background command prompt to run the program you write after it (source: https://technet.microsoft.com/en-us/library/cc770297(v=ws.11).aspx). Is this the same as Linux's myApp & format--where you have the & suffix?
Starting a Program
See start /? and call /? for help on all three ways.
Specify a program name
c:\windows\notepad.exe
In a batch file the batch will wait for the program to exit. When
typed the command prompt does not wait for graphical
programs to exit.
If the program is a batch file control is transferred and the rest of the calling batch file is not executed.
Use Start command
start "" c:\windows\notepad.exe
Start starts a program and does not wait. Console programs start in a new window. Using the /b switch forces console programs into the same window, which negates the main purpose of Start.
Start uses the Windows graphical shell - same as typing in WinKey + R (Run dialog). Try
start shell:cache
Also note the first set of quotes, if any, MUST be the window title.
Use Call command
Call is used to start batch files and wait for them to exit and continue the current batch file.
With Reference to Start and just typing a program name.
Help Windows Find Programs and Documents
Programs and documents can be added to the registry so typing their name without their path in the Start - Run dialog box or shortcut enables Windows to find them.
REGEDIT4
;The bolded name below is the name of the document or program, <filename>.<file extension>
[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\App Paths\IE.txt]
;The # means the path to the file is assigned to the default value for the key.
;The whole path in enclosed in a quotation mark ".
#="\"C:\\Program Files\\Internet Explorer\\IE.txt\""
;Optional Parameters. The semicolon means don't process the line. Remove it if you want to put it in the registry
;Informs the shell that the program accepts URLs.
;"useURL"="1"
;Sets the path that a program will use as its' default directory. This is commented out.
;"Path"="C:\\Program Files\\Microsoft Office\\Office\\"
For a technical discussion.
CMD preprocesses commands and finds the file then calls CreateProcess. Start - Run dialog or the Start command uses ShellExecuteEx which eventually calls CreateProcess.
This is CreateProcess rules - note CMD provides full paths to CreateProcess. https://msdn.microsoft.com/en-us/library/ms682425
1.The directory from which the application loaded.
2.The current directory for the parent process.
3.The 32-bit Windows system directory. Use the GetSystemDirectory function to get the path of this directory.
The 16-bit Windows system directory. There is no function that obtains the path of this directory, but it is searched. The name of this directory is System.
5.The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
6.The directories that are listed in the PATH environment variable. Note that this function does not search the per-application path specified by the App Paths registry key. To include this per-application path in the search sequence, use the ShellExecute function.
ShellExecuteEx is here https://msdn.microsoft.com/en-us/library/bb759784(v=vs.85).aspx
CMD preprocessing is available on my Skydrive - originally from MS web site but no more. See Windows NT Command Shell Ch 2 https://1drv.ms/f/s!AvqkaKIXzvDieQFjUcKneSZhDjw
you need to call start application when you want the application to launch and return immediately to the command shell for further commands.
(on Linux, closest equivalent of start is the & suffix)
Some commands have the ability to do that without start prefix. That's what you're experiencing.
On the other hand, if you want an application returning immediately to "block" the shell, prefix by cmd /c
Try cmd /c taskmgr for instance, you'll see it blocks the command window until you quit it.
About the question about taskmgr, the 3 possibilities amount to the same result:
taskmgr is in system path: with or without full path the system finds it
taskmgr returns to the command window immediately. In that case, start is redundant.
I'm curious why commands like "start iexplore" and "start firefox" work in Windows cmd.
They're not standalone commands. If you try to type in just "firefox", you'll get:
"'firefox' is not recognized as an internal or external command,
operable program or batch file."
This leads to the conclusion that this is a special behaviour of the "start" command.
My first guess was that it works in a similar way to how the %path% variable is used, having known directories to search in.
I ruled it out easily by trying to run "start [executable]" for another executable located in the same directory as firefox.
My conclusion is that somewhere on my computer there's a list of designated file paths, that can be started by simply typing their file name after the "start" command, instead of the entire path.
Imagine the potential of being able to add things to this list..
Anyone knows where I can find it?
It is in the registry
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\
Under this key there are defined applications that can be invoked without need to change the path environment variable.
Usual invocation (typing the name in the command line) will not search inside this list, but call to start command, windows Run dialog or call from anything that uses the ShellExecute or ShellExecuteEx API calls, will check for applications defined in this list.
I am running Windows 7x64 and Excel 2010x32. I call 32bit dos programs (written in Fortran) via vba using ExecCmd (a Microsoft function that waits for a command prompt process to finish). I send a command line to this function that explicitly contains the program path and the paths of the input file and output file.
This runs fine on my PC and also on a company PC running the same software (OS and Office) and for which I have general access to the C: drive.
On other company PCs, where there is not general access to the C: drive, this does not work - i.e. the dos programs do not produce an output file. On these PCs, I can still run the program at the command prompt manually. It is just that calling this command prompt does not work via Excel VBA.
Now the strange thing is that I can successfully run one of these programs by adding "cmd.exe /c" at the beginning of the command line. That would appear to be running a command prompt within a command prompt (!). The other program (which, incidentally, is quite a bit bigger) does not work at all via vba on these PCs. I need to be able to provide other employees with something that works.
Can anyone shed some light on what is happening here and suggest a work around? I could past some code, but I think the above should be self explanatory.
You're confusing the command shell with the console window. In this context, the distinction is critical.
Console-mode programs (aka "command-line programs") require a console window to provide input and output. When a console-mode program is launched from a GUI program, Windows automatically creates a console window for it (unless instructed otherwise).
The command shell (aka "Command Prompt") is cmd.exe, a console-mode program.
The important point here is that not every console window has an instance of cmd.exe running in it. When a console-mode program is launched from a GUI program, Windows automatically creates a console window but does not automatically create an instance of cmd.exe. If you want to pass a command to cmd.exe you have to do so yourself, or use a run-time library routine that does it for you.
ExecCmd does not do this; it runs the program directly. So passing cmd /c <command> to ExecCmd is not "running a command prompt within a command prompt" at all. Without the cmd /c you aren't running a command shell command, you're just launching an executable.
There are any number of reasons why the command you're passing might need to be given to the command shell. For example:
it might be a built-in command like dir or type which only exists within the command shell;
it might include redirection or pipelining operators, or environment variable substitution;
it might be a script rather than an executable.
There are other cases. If you show us the command line being passed to ExecCmd we may be able to provide more specific advice. (The fact that the same command line is apparently working on some machines is puzzling, but can't be addressed without more information.)
How do i launch firefox from perl? i just need to launch the browser so WWW::Mechanize::Firefox can manipulate it. Searching around stackoverflow ive seen a few solutionsl like system('start cmd.exe /k $cmd) where $cmd is arguments to throw as input once cmd is started.
However, these have not helped me to solve my problem at all.
solutions ive tried
system("start cmd.exe /k start firefox");
system("firefox");
system("cmd","start","firefox");
system("cmd start firefox");
Basically a lot of the alternatives ive found, but i could not launch Firefox browser at all.
You're on the right track. Your second line is almost correct. If firefox is not in your PATH environment variable, you need to supply the complete path.
Click on the Firefox icon on your desktop, open the properties and check where the firefox executable is located. Then use that with your system call.
For me, it looks like this (the ' are for Perl's string, the " are for the Windows shell, because the path has spaces in it):
system('"C:\Programme\Mozilla Firefox\firefox.exe"');
You can test it by opening a new command line (win + r, cmd), cding to the directory where your Perl program is run from, and just entering the command:
C:\Dokumente und Einstellungen\simbabque>"C:\Programme\Mozilla Firefox\firefox.exe"
It will not print anything, but just open a new Firefox window after a couple of seconds. So you'd probably need to hold your program execution in Perl while the browser is starting up.
WWW::Mechanize::Firefox will launch firefox for you but you can use
system 1, qq{$ENV{PROGRAMFILES}\\Mozilla Firefox\\firefox.exe}