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A collection of Delphi environment variable routines presented in the article "How to access environment variables" at http://delphidabbler.com/articles?article=6
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unit UEnvVars; | |
interface | |
uses | |
// Delphi | |
Classes; | |
function GetEnvVarValue(const VarName: string): string; | |
function SetEnvVarValue(const VarName, VarValue: string): Integer; | |
function DeleteEnvVar(const VarName: string): Integer; | |
function CreateEnvBlock(const NewEnv: TStrings; const IncludeCurrent: Boolean; | |
const Buffer: Pointer; const BufSize: Integer): Integer; | |
function ExpandEnvVars(const Str: string): string; | |
function GetAllEnvVars(const Vars: TStrings): Integer; | |
implementation | |
uses | |
// Delphi | |
Windows, SysUtils; | |
function GetEnvVarValue(const VarName: string): string; | |
var | |
BufSize: Integer; // buffer size required for value | |
begin | |
// Get required buffer size (inc. terminal #0) | |
BufSize := GetEnvironmentVariable(PChar(VarName), nil, 0); | |
if BufSize > 0 then | |
begin | |
// Read env var value into result string | |
SetLength(Result, BufSize - 1); | |
GetEnvironmentVariable(PChar(VarName), PChar(Result), BufSize); | |
end | |
else | |
// No such environment variable | |
Result := ''; | |
end; | |
function SetEnvVarValue(const VarName, VarValue: string): Integer; | |
begin | |
if SetEnvironmentVariable(PChar(VarName), PChar(VarValue)) then | |
Result := 0 | |
else | |
Result := GetLastError; | |
end; | |
function DeleteEnvVar(const VarName: string): Integer; | |
begin | |
if SetEnvironmentVariable(PChar(VarName), nil) then | |
Result := 0 | |
else | |
Result := GetLastError; | |
end; | |
function CreateEnvBlock(const NewEnv: TStrings; | |
const IncludeCurrent: Boolean; const Buffer: Pointer; | |
const BufSize: Integer): Integer; | |
var | |
EnvVars: TStringList; // env vars in new block | |
Idx: Integer; // loops thru env vars | |
PBuf: PChar; // start env var entry in block | |
begin | |
// String list for new environment vars | |
EnvVars := TStringList.Create; | |
try | |
// include current block if required | |
if IncludeCurrent then | |
GetAllEnvVars(EnvVars); | |
// store given environment vars in list | |
if Assigned(NewEnv) then | |
EnvVars.AddStrings(NewEnv); | |
// Calculate size of new environment block | |
Result := 0; | |
for Idx := 0 to Pred(EnvVars.Count) do | |
Inc(Result, Length(EnvVars[Idx]) + 1); | |
Inc(Result); | |
// Create block if buffer large enough | |
if (Buffer <> nil) and (BufSize >= Result) then | |
begin | |
// new environment blocks are always sorted | |
EnvVars.Sorted := True; | |
// do the copying | |
PBuf := Buffer; | |
for Idx := 0 to Pred(EnvVars.Count) do | |
begin | |
StrPCopy(PBuf, EnvVars[Idx]); | |
Inc(PBuf, Length(EnvVars[Idx]) + 1); | |
end; | |
// terminate block with additional #0 | |
PBuf^ := #0; | |
end; | |
finally | |
EnvVars.Free; | |
end; | |
end; | |
function ExpandEnvVars(const Str: string): string; | |
var | |
BufSize: Integer; // size of expanded string | |
begin | |
// Get required buffer size | |
BufSize := ExpandEnvironmentStrings(PChar(Str), nil, 0); | |
if BufSize > 0 then | |
begin | |
// Read expanded string into result string | |
SetLength(Result, BufSize); | |
ExpandEnvironmentStrings(PChar(Str), PChar(Result), BufSize); | |
end | |
else | |
// Trying to expand empty string | |
Result := ''; | |
end; | |
function GetAllEnvVars(const Vars: TStrings): Integer; | |
var | |
PEnvVars: PChar; // pointer to start of environment block | |
PEnvEntry: PChar; // pointer to an env string in block | |
begin | |
// Clear the list | |
if Assigned(Vars) then | |
Vars.Clear; | |
// Get reference to environment block for this process | |
PEnvVars := GetEnvironmentStrings; | |
if PEnvVars <> nil then | |
begin | |
// We have a block: extract strings from it | |
// Env strings are #0 separated and list ends with #0#0 | |
PEnvEntry := PEnvVars; | |
try | |
while PEnvEntry^ <> #0 do | |
begin | |
if Assigned(Vars) then | |
Vars.Add(PEnvEntry); | |
Inc(PEnvEntry, StrLen(PEnvEntry) + 1); | |
end; | |
// Calculate length of block | |
Result := (PEnvEntry - PEnvVars) + 1; | |
finally | |
// Dispose of the memory block | |
Windows.FreeEnvironmentStrings(PEnvVars); | |
end; | |
end | |
else | |
// No block => zero length | |
Result := 0; | |
end; | |
end. |
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