> How can I get all environment variables reliable?
> I need to store them temporarily and pass them
> later on as environment block to CreateProcess().
> Is it save to call GetEnvironmentVariable() on each returned name?
Why not use Windows API function GetEnvironmentStrings ? It returns a pointer
to the environment
block. It think it is perfectly suited for apssing it to CreateProcess. If you
need to change the
environment variables before apssing it to CreateProcess, use the code below
(Extracted from MSDN):
Changing Environment Variables
Each process has an environment block associated with it. The environment block
consists of a
null-terminated block of null-terminated strings (meaning there are two null
bytes at the end of the
block), where each string is in the form:
name=value
All strings in the environment block must be sorted alphabetically by name. The
sort is
case-insensitive, Unicode order, without regard to locale. Because the equal
sign is a separator, it
must not be used in the name of an environment variable.
By default, a child process inherits a copy of the environment block of the
parent process. The
following example demonstrates how to create a new environment block to pass to
a child process.
LPTSTR lpszCurrentVariable;
BOOL fSuccess;
// Copy environment strings into an environment block.
lpszCurrentVariable = tchNewEnv;
if (lstrcpy(lpszCurrentVariable, "MyVersion=2") == NULL)
ErrorExit("lstrcpy failed");
lpszCurrentVariable += lstrlen(lpszCurrentVariable) + 1;
if (lstrcpy(lpszCurrentVariable, "MySetting=A") == NULL)
ErrorExit("lstrcpy failed");
// Terminate the block with a NULL byte.
lpszCurrentVariable += lstrlen(lpszCurrentVariable) + 1;
*lpszCurrentVariable = '\0';
// Create the child process, specifying a new environment block.
fSuccess = CreateProcess(NULL, "childenv", NULL, NULL, TRUE, 0,
(LPVOID) tchNewEnv, // new environment block
NULL, &siStartInfo, &piProcInfo);
if (! fSuccess)
ErrorExit("CreateProcess failed");
If you want the child process to inherit most of the parent's environment with
only a few changes,
save the current values, make changes for the child process to inherit, create
the child process,
and then restore the saved values, as shown following.
LPTSTR lpszOldValue;
TCHAR tchBuf[BUFSIZE];
BOOL fSuccess;
// lpszOldValue gets current value of "varname", or NULL if "varname"
// environment variable does not exist. Set "varname" to new value,
// create child process, then use SetEnvironmentVariable to restore
// original value of "varname". If lpszOldValue is NULL, the "varname"
// variable will be deleted.
lpszOldValue = ((GetEnvironmentVariable("varname",
tchBuf, BUFSIZE) > 0) ? tchBuf : NULL);
// Set a value for the child process to inherit.
if (! SetEnvironmentVariable("varname", "newvalue"))
ErrorExit("SetEnvironmentVariable failed");
// Create a child process.
fSuccess = CreateProcess(NULL, "childenv", NULL, NULL, TRUE, 0,
NULL, // inherit parent's environment
NULL, &siStartInfo, &piProcInfo);
if (! fSuccess)
ErrorExit("CreateProcess failed");
// Restore the parent's environment.
if (! SetEnvironmentVariable("varname", lpszOldValue))
ErrorExit("SetEnvironmentVariable failed");Note that altering the
environment variables of a
child process during process creation is the only way one process can directly
change the
environment variables of another process. A process can never directly change
the environment
variables of another process that is not a child of that process.
The following example, taken from a console process, prints the contents of the
process's
environment block.
LPTSTR lpszVariable;
LPVOID lpvEnv;
// Get a pointer to the environment block.
lpvEnv = GetEnvironmentStrings();
// If the returned pointer is NULL, exit.
if (lpvEnv == NULL)
ErrorExit("GetEnvironmentStrings failed.");
// Variable strings are separated by NULL byte, and the block is
// terminated by a NULL byte.
for (lpszVariable = (LPTSTR) lpvEnv; *lpszVariable; lpszVariable++)
{
while (*lpszVariable)
putchar(*lpszVariable++);
putchar('\n');
}
FreeEnvironmentStrings(lpvEnv);[EMAIL PROTECTED] of ICS (Internet Component
Suite,
freeware)Author of MidWare (Multi-tier framework,
freeware)http://www.overbyte.be
_______________________________________________
Delphi mailing list -> [email protected]
http://www.elists.org/mailman/listinfo/delphi
