|
| System.Process | | Portability | non-portable (requires concurrency) | | Stability | experimental | | Maintainer | libraries@haskell.org |
|
|
|
|
|
| Description |
| Operations for creating and interacting with sub-processes.
|
|
| Synopsis |
|
| createProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) | | | shell :: String -> CreateProcess | | | proc :: FilePath -> [String] -> CreateProcess | | | data CreateProcess = CreateProcess {} | | | | | | | data ProcessHandle | | | runCommand :: String -> IO ProcessHandle | | | runProcess :: FilePath -> [String] -> Maybe FilePath -> Maybe [(String, String)] -> Maybe Handle -> Maybe Handle -> Maybe Handle -> IO ProcessHandle | | | runInteractiveCommand :: String -> IO (Handle, Handle, Handle, ProcessHandle) | | | runInteractiveProcess :: FilePath -> [String] -> Maybe FilePath -> Maybe [(String, String)] -> IO (Handle, Handle, Handle, ProcessHandle) | | | readProcess :: FilePath -> [String] -> String -> IO String | | | readProcessWithExitCode :: FilePath -> [String] -> String -> IO (ExitCode, String, String) | | | system :: String -> IO ExitCode | | | rawSystem :: String -> [String] -> IO ExitCode | | | waitForProcess :: ProcessHandle -> IO ExitCode | | | getProcessExitCode :: ProcessHandle -> IO (Maybe ExitCode) | | | terminateProcess :: ProcessHandle -> IO () |
|
|
|
| Running sub-processes
|
|
|
This is the most general way to spawn an external process. The
process can be a command line to be executed by a shell or a raw command
with a list of arguments. The stdin, stdout, and stderr streams of
the new process may individually be attached to new pipes, to existing
Handles, or just inherited from the parent (the default.)
The details of how to create the process are passed in the
CreateProcess record. To make it easier to construct a
CreateProcess, the functions proc and shell are supplied that
fill in the fields with default values which can be overriden as
needed.
createProcess returns (mb_stdin_hdl, mb_stdout_hdl, mb_stderr_hdl, p),
where
- if std_in == CreatePipe, then mb_stdin_hdl will be Just h,
where h is the write end of the pipe connected to the child
process's stdin.
- otherwise, mb_stdin_hdl == Nothing
Similarly for mb_stdout_hdl and mb_stderr_hdl.
For example, to execute a simple ls command:
r <- createProcess (proc "ls" [])
To create a pipe from which to read the output of ls:
(_, Just hout, _, _) <-
createProcess (proc "ls" []){ std_out = CreatePipe }
To also set the directory in which to run ls:
(_, Just hout, _, _) <-
createProcess (proc "ls" []){ cwd = Just "\home\bob",
std_out = CreatePipe }
|
|
|
| Construct a CreateProcess record for passing to createProcess,
representing a command to be passed to the shell.
|
|
|
| Construct a CreateProcess record for passing to createProcess,
representing a raw command with arguments.
|
|
|
| Constructors | | CreateProcess | | | cmdspec :: CmdSpec | Executable & arguments, or shell command
| | cwd :: Maybe FilePath | Optional path to the working directory for the new process
| | env :: Maybe [(String, String)] | Optional environment (otherwise inherit from the current process)
| | std_in :: StdStream | How to determine stdin
| | std_out :: StdStream | How to determine stdout
| | std_err :: StdStream | How to determine stderr
| | close_fds :: Bool | Close all file descriptors except stdin, stdout and stderr in the new process (on Windows, only works if std_in, std_out, and std_err are all Inherit)
|
|
|
|
|
|
| Constructors | | ShellCommand String | a command line to execute using the shell
| | RawCommand FilePath [String] | the filename of an executable with a list of arguments
|
|
|
|
|
| Constructors | | Inherit | Inherit Handle from parent
| | UseHandle Handle | Use the supplied Handle
| | CreatePipe | Create a new pipe
|
|
|
|
|
|
| Specific variants of createProcess
|
|
|
| Runs a command using the shell.
|
|
|
| :: FilePath | Filename of the executable
| | -> [String] | Arguments to pass to the executable
| | -> Maybe FilePath | Optional path to the working directory
| | -> Maybe [(String, String)] | Optional environment (otherwise inherit)
| | -> Maybe Handle | Handle to use for stdin (Nothing => use existing stdin)
| | -> Maybe Handle | Handle to use for stdout (Nothing => use existing stdout)
| | -> Maybe Handle | Handle to use for stderr (Nothing => use existing stderr)
| | -> IO ProcessHandle | | Runs a raw command, optionally specifying Handles from which to
take the stdin, stdout and stderr channels for the new
process (otherwise these handles are inherited from the current
process).
Any Handles passed to runProcess are placed immediately in the
closed state.
Note: consider using the more general createProcess instead of
runProcess.
|
|
|
|
| Runs a command using the shell, and returns Handles that may
be used to communicate with the process via its stdin, stdout,
and stderr respectively. The Handles are initially in binary
mode; if you need them to be in text mode then use hSetBinaryMode.
|
|
|
| :: FilePath | Filename of the executable
| | -> [String] | Arguments to pass to the executable
| | -> Maybe FilePath | Optional path to the working directory
| | -> Maybe [(String, String)] | Optional environment (otherwise inherit)
| | -> IO (Handle, Handle, Handle, ProcessHandle) | | Runs a raw command, and returns Handles that may be used to communicate
with the process via its stdin, stdout and stderr respectively.
For example, to start a process and feed a string to its stdin:
(inp,out,err,pid) <- runInteractiveProcess "..."
forkIO (hPutStr inp str)
The Handles are initially in binary mode; if you need them to be
in text mode then use hSetBinaryMode.
|
|
|
|
| :: FilePath | command to run
| | -> [String] | any arguments
| | -> String | standard input
| | -> IO String | stdout + stderr
| readProcess forks an external process, reads its standard output
strictly, blocking until the process terminates, and returns either the output
string, or, in the case of non-zero exit status, an error code, and
any output.
Output is returned strictly, so this is not suitable for
interactive applications.
Users of this function should compile with -threaded if they
want other Haskell threads to keep running while waiting on
the result of readProcess.
> readProcess "date" [] []
Right "Thu Feb 7 10:03:39 PST 2008\n"
The argumenst are:
- The command to run, which must be in the $PATH, or an absolute path
- A list of separate command line arguments to the program
- A string to pass on the standard input to the program.
|
|
|
|
| :: FilePath | command to run
| | -> [String] | any arguments
| | -> String | standard input
| | -> IO (ExitCode, String, String) | exitcode, stdout, stderr
| readProcessWithExitCode creates an external process, reads its
standard output and standard error strictly, waits until the process
terminates, and then returns the ExitCode of the process,
the standard output, and the standard error.
readProcess and readProcessWithExitCode are fairly simple wrappers
around createProcess. Constructing variants of these functions is
quite easy: follow the link to the source code to see how
readProcess is implemented.
|
|
|
|
Computation system cmd returns the exit code produced when the
operating system runs the shell command cmd.
This computation may fail with
- PermissionDenied: The process has insufficient privileges to
perform the operation.
- ResourceExhausted: Insufficient resources are available to
perform the operation.
- UnsupportedOperation: The implementation does not support
system calls.
On Windows, system passes the command to the Windows command
interpreter (CMD.EXE or COMMAND.COM), hence Unixy shell tricks
will not work.
|
|
|
The computation rawSystem cmd args runs the operating system command
cmd in such a way that it receives as arguments the args strings
exactly as given, with no funny escaping or shell meta-syntax expansion.
It will therefore behave more portably between operating systems than system.
The return codes and possible failures are the same as for system.
|
|
| Process completion
|
|
|
Waits for the specified process to terminate, and returns its exit code.
GHC Note: in order to call waitForProcess without blocking all the
other threads in the system, you must compile the program with
-threaded.
|
|
|
| This is a non-blocking version of waitForProcess. If the process is
still running, Nothing is returned. If the process has exited, then
Just e is returned where e is the exit code of the process.
Subsequent calls to getProcessExitStatus always return Just
ExitSuccess, regardless of what the original exit code was.
|
|
|
Attempts to terminate the specified process. This function should
not be used under normal circumstances - no guarantees are given regarding
how cleanly the process is terminated. To check whether the process
has indeed terminated, use getProcessExitCode.
On Unix systems, terminateProcess sends the process the SIGTERM signal.
On Windows systems, the Win32 TerminateProcess function is called, passing
an exit code of 1.
|
|
| Produced by Haddock version 2.4.2 |
