Using ShellExecute to send sqlite3.exe a shell script - c++

Question

I've got the following shell script in file c:/SQLiteData/Cmnds.txt
.open c:/SQLiteData/LGMeta.db
create table Temp {f INTEGER primary key};
insert into Temp values(-1);
.output c:/SQLiteData/Out.txt
select * from Temp;
I tried running it inside a c++ programme using
ShellExecute(NULL, L"open", L"c:/SQLiteData/sqlite3.exe",
L".read c:/SQLiteData/Cmnds.txt", NULL, 0);
ShellExecute returns 42 which suggests success but nothing happens. Neither Temp or Out.txt are created. Can anyone tell me what I'm missing?
EDIT
Thanks for the replies. I've spent the last 3 days tearing my hair out with this stuff. I patched this together from several posts on the subject
unsigned int RunCmnd(String CmndLine)
{
STARTUPINFO StartupInfo;
PROCESS_INFORMATION ProcessInfo;
memset(&ProcessInfo,0,sizeof(ProcessInfo)); // setup memory blocks
memset(&StartupInfo,0,sizeof(StartupInfo));
StartupInfo.cb=sizeof(StartupInfo); // set structure size
StartupInfo.wShowWindow=SW_HIDE; // hide window
if (CreateProcess(NULL,CmndLine.c_str(),
NULL,NULL,false,0,NULL,NULL,&StartupInfo,&ProcessInfo))
{
WaitForSingleObject(ProcessInfo.hThread,INFINITE);
return 0;
}
else return GetLastError();
}
If I start up the command shell and enter the following line
c:/SQLiteData/sqlite3.exe < c:/SQLiteData/Cmnds.txt
everything works as expected BUT if use
RunCmnd("c:/SQLiteData/sqlite3.exe < c:/SQLiteData/Cmnds.txt")
from within my c++ builder app nothing happens. I'm missing something fundamental here. Can anyone tell me what?

Answer 1

Finally came up with this which was adapted from an excellent post by TarmoPikaro on this thread
How to execute a command and get output of command within C++ using POSIX?.
String TempFileName(bool ForwardSlash) // ForwardSlash default = true
{
wchar_t Nm[MAX_PATH],Path[MAX_PATH];
GetTempPath(MAX_PATH,Path);
if (!GetTempFileName(Path,L"",0,Nm))
throw Exception(String("TempFileName failed - ")+
SysErrorMessage(GetLastError()));
String Name=Nm;
if (ForwardSlash)
for (int Len=Name.Length(),i=1; i<=Len; i++) if (Name[i]=='\\') Name[i]='/';
return Name;
}
//---------------------------------------------------------------------------
String SQLiteExe(String DB,String OutFile,String Cmds)
{
// Returns first error message if process doesn't execute cleanly. Otherwise
// if OutFile=="" it returns the output
// if Outfile>"" the output is sent to OutFile and return is NULL.
String Output;
HANDLE hPipeRead,hPipeWrite;
SECURITY_ATTRIBUTES saAttr={sizeof(SECURITY_ATTRIBUTES)};
saAttr.bInheritHandle=TRUE; //Pipe handles are inherited by child process.
saAttr.lpSecurityDescriptor=NULL;
// Create a pipe to get output from child's stdout.
if (!CreatePipe(&hPipeRead,&hPipeWrite,&saAttr,0))
return "Error: Unable to create pipe";
STARTUPINFO si={sizeof(STARTUPINFO)};
si.dwFlags=STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
si.hStdOutput=hPipeWrite;
si.hStdError=hPipeWrite;
si.wShowWindow=SW_HIDE;
// Prevents cmd window from flashing. Requires STARTF_USESHOWWINDOW in dwFlags.
TStringList *Batch=new TStringList;
Batch->StrictDelimiter=true;
Batch->Delimiter=';';
Batch->DelimitedText=Cmds;
if (OutFile>"") Batch->Insert(0,".output "+OutFile);
String S;
for (int i=0; i<Batch->Count; i++)
{
Batch->Strings[i]=Batch->Strings[i].Trim();
// .commands must have dot as first char on line
if (Batch->Strings[i]=="") continue;
S+=Batch->Strings[i]+(Batch->Strings[i][1]=='.' ? "" : ";")+"\r\n";
}
Batch->Text=S;
String BatchFile=TempFileName();
Batch->SaveToFile(BatchFile);
delete Batch;
String Cmd="sqlite3 "+DB+" \".read "+BatchFile+"\""; // assumes sqlite3.exe in PATH
PROCESS_INFORMATION pi={0};
BOOL fSuccess=CreateProcessW(NULL,Cmd.c_str(),NULL,NULL,TRUE,CREATE_NEW_CONSOLE,
NULL,NULL, &si, &pi);
if (! fSuccess)
{
CloseHandle(hPipeWrite);
CloseHandle(hPipeRead);
DeleteFile(BatchFile);
return "Error: Failed to create process";
}
bool bProcessEnded=false;
while (!bProcessEnded)
{
// Give some timeslice (50ms), so we won't waste 100% cpu.
bProcessEnded=WaitForSingleObject(pi.hProcess,50)==WAIT_OBJECT_0;
// Even if process exited - we continue reading, if there is some data available
// over pipe.
while (true)
{
char buf[1024];
DWORD dwRead=0;
DWORD dwAvail=0;
if (!::PeekNamedPipe(hPipeRead,NULL,0,NULL,&dwAvail,NULL)) break;
if (!dwAvail) break; // no data available, return
if (!::ReadFile(hPipeRead,buf,std::min(sizeof(buf)-1,
(unsigned int)(dwAvail)),&dwRead,NULL) || !dwRead)
break; // error, the child process might ended
buf[dwRead]=0;
Output+=buf;
}
int p=Output.Pos("Error:"); // if (p) return first error message
if (p) {Output.Delete(1,p-1); Output.Delete(Output.Pos("\r\n"),Output.Length());}
}
DeleteFile(BatchFile); // NB can't be deleted until ProcessEnded
CloseHandle(hPipeWrite);
CloseHandle(hPipeRead);
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
return Output;
}
//---------------------------------------------------------------------------
Usage
String Err=SQLiteExe("c:/SQLiteData/MyDB.db","c:/SQLiteData/MyTblDump.txt"",
".mode csv; select * from MyTbl;");
if (Err>"") throw Exception(Err);
else ........
Multiple commands should be separated by semi-colons. SQLiteExe automatically removes the redundant semi-colons at the end of lines starting with a dot.