[Gambas-user] Using EXEC

[Stephen Bungay]

On 08/31/2011 09:01 PM, Benoît Minisini wrote:
>> EXEC is a wonderful thing, lighter than SHELL, but it needs things
>> passed as elements of a string array and that is making for some ugly code.
>>
>> Say for example you want to play two videos as a playlist in VLC, in
>> exec the command might look like this;
>>
>> EXEC["vlc","--intf","rc", "Video1.avi","Video2.avi"]
>>
>> But what if you had different quantities of videos to play, lets say
>> next time you needed to play 4 videos? How would you use EXEC to do this?
>>
>>
>> I thought of building the string and embedding the quotes in it like this;
>>
>> ExecString = chr$(34)&  "vlc"&  chr$(34)&  ","&  chr$(34)&  "--intf"&
>> chr$(34)&  ","&  chr$(34)&  "rc"&  chr$(34)&  ","
>> For X= 0 TO sFile.Count - 1
>>         ExecString = ExecString&  chr$934)&  sFile[X]&  chr$(34)
>>         IF X<  sFile.Count -1 then
>>            ExecString = ExecString&  ","
>>        End IF
>> NEXT
>>
>> Which would result in a string that looks like this;
>>
>> "vlc", "--intf", "rc", "video1.avi", "video2.avi"
>>
>> Nope. It sees the one string as one element when what I want is the
>> contents of the string to be inserted as multiple elements.
>>
>> At the moment I am fetching the video file names from a directory
>> listing, splitting that up into an array, then checking the number of
>> elements in the array and using a case statement to do the work...
>>
>> SELECT CASE sFile.Count
>>             CASE 1
>>                  mpProcessHandle = EXEC ["vlc", "--intf", "rc", sFile[0]]
>> FOR INPUT OUTPUT AS "VLC"
>>             CASE 2
>>                  mpProcessHandle = EXEC ["vlc", "--intf", "rc", sFile[0],
>> sFile[1]] FOR INPUT OUTPUT AS "VLC"
>>             CASE 3
>>                  mpProcessHandle = EXEC ["vlc", "--intf", "rc", sFile[0],
>> sFile[1], sFile[2]] FOR INPUT OUTPUT AS "VLC"
>>             CASE 4
>>                  mpProcessHandle = EXEC ["vlc", "--intf", "rc", sFile[0],
>> sFile[1], sFile[2]] FOR INPUT OUTPUT AS "VLC"
>> END SELECT
>>
>> It ain't pretty. "sFile" is a string array derived from another string
>> that contains the names of videos which in my case are delimited by
>> spaces. Definetly the brute-force/bulldozer approach, big, ugly, and
>> cumbersome, but it does work. Does anyone else know of a more elegant
>> solution?
>>
>> Regards
>> Steve.
>>
> [ ... ] is not a compiler thing, but an operator that build an array at
> runtime.
>
> So you can make the EXEC array with "New String[]" and populate it as you
> need:
>
>    Dim aFile As String[] ' The files to open
>    Dim aArg As String[]
>
>    aArg = ["vlc", "--intf", "rc"]
>    aArg.Insert(aFile)
>    Exec aArg For Input Output As "VLC"
>
> Regards,
>
Works like a jet.