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system |
The stdlib_system module provides interface for interacting with external processes, enabling the execution
and monitoring of system commands or applications directly from Fortran.
[TOC]
Experimental
The run interface allows execution of external processes using a single command string or a list of arguments.
Processes run synchronously, meaning execution is blocked until the process finishes.
Optional arguments enable the collection of standard output and error streams, as well as sending input via standard input.
Additionally, a callback function can be specified to execute upon process completion, optionally receiving a user-defined payload.
process = [[stdlib_subprocess(module):run(interface)]] (args [, stdin] [, want_stdout] [, want_stderr] [, callback] [, payload])
args: Shall be a character(*) string (for command-line execution) or a character(*), dimension(:) array (for argument-based execution). It specifies the command and arguments to execute. This is an intent(in) argument.
stdin (optional): Shall be a character(*) value containing input to send to the process via standard input (pipe). This is an intent(in) argument.
want_stdout (optional): Shall be a logical flag. If .true., the standard output of the process will be captured; if .false. (default), it will be lost. This is an intent(in) argument.
want_stderr (optional): Shall be a logical flag. If .true., the standard error output of the process will be captured. If .false. (default), it will be lost. This is an intent(in) argument.
callback (optional): Shall be a procedure conforming to the process_callback interface. If present, this function will be called upon process completion with the process ID, exit state, and optionally collected standard input, output, and error streams. This is an intent(in) argument.
payload (optional): Shall be a generic (class(*)) scalar that will be passed to the callback function upon process completion. It allows users to associate custom data with the process execution. This is an intent(inout), target argument.
Returns an object of type process_type that contains information about the state of the created process.
! Example usage with command line or list of arguments
type(process_type) :: p
! Run a simple command line synchronously
p = run("echo 'Hello, world!'", want_stdout=.true.)Experimental
The runasync interface allows execution of external processes using a single command string or a list of arguments.
Processes are run asynchronously (non-blocking), meaning execution does not wait for the process to finish.
Optional arguments enable the collection of standard output and error streams, as well as sending input via standard input.
Additionally, a callback function can be specified to execute upon process completion, optionally receiving a user-defined payload.
process = [[stdlib_subprocess(module):runasync(interface)]] (args [, stdin] [, want_stdout] [, want_stderr] [, callback] [, payload])
args: Shall be a character(*) string (for command-line execution) or a character(*), dimension(:) array (for argument-based execution). It specifies the command and arguments to execute. This is an intent(in) argument.
stdin (optional): Shall be a character(*) value containing input to send to the process via standard input (pipe). This is an intent(in) argument.
want_stdout (optional): Shall be a logical flag. If .true., the standard output of the process will be captured; if .false. (default), it will be lost. This is an intent(in) argument.
want_stderr (optional): Shall be a logical flag. If .true., the standard error output of the process will be captured. Default: .false.. This is an intent(in) argument.
callback (optional): Shall be a procedure conforming to the process_callback interface. If present, this function will be called upon process completion with the process ID, exit state, and optionally collected standard input, output, and error streams. This is an intent(in) argument.
payload (optional): Shall be a generic (class(*)) scalar that will be passed to the callback function upon process completion. It allows users to associate custom data with the process execution. This is an intent(inout), target argument.
Returns an object of type process_type that contains information about the state of the created process.
{!example/system/example_process_1.f90!}Experimental
The is_running interface provides a method to check if an external process is still running.
This is useful for monitoring the status of asynchronous processes created with the run interface.
status = [[stdlib_subprocess(module):is_running(interface)]] (process)
process: Shall be a type(process_type) object representing the external process to check. This is an intent(inout) argument.
Returns a logical value: .true. if the process is still running, or .false. if the process has terminated.
After a call to is_running, the type(process_type) structure is also updated to the latest process state.
{!example/system/example_process_2.f90!}Experimental
The is_completed interface provides a method to check if an external process has finished execution.
This is useful for determining whether asynchronous processes created with the run interface have terminated.
status = [[stdlib_subprocess(module):is_completed(interface)]] (process)
process: Shall be a type(process_type) object representing the external process to check. This is an intent(inout) argument.
Returns a logical value:
.true.if the process has completed..false.if the process is still running.
After a call to is_completed, the type(process_type) structure is updated to reflect the latest process state.
{!example/system/example_process_1.f90!}Experimental
The elapsed interface provides a method to calculate the total time that has elapsed since a process was started.
This is useful for tracking the duration of an external process or for performance monitoring purposes.
The result is a real value representing the elapsed time in seconds, measured from the time the process was created.
delta_t = [[stdlib_subprocess(module):elapsed(subroutine)]] (process)
process: Shall be a type(process_type) object representing the external process. It is an intent(in) argument.
Returns a real(real64) value that represents the elapsed time (in seconds) since the process was started.
If the process is still running, the value returned is the time elapsed until the call to this function.
Otherwise, the total process duration from creation until completion is returned.
{!example/system/example_process_3.f90!}Experimental
The wait interface provides a method to block the calling program until the specified process completes.
If the process is running asynchronously, this subroutine will pause the workflow until the given process finishes.
Additionally, an optional maximum wait time can be provided. If the process does not finish within the specified time,
the subroutine will return without waiting further.
On return from this routine, the process state is accordingly updated. This is useful when you want to wait for a background task to complete, but want to avoid indefinite blocking in case of process hang or delay.
call [[stdlib_subprocess(module):wait(subroutine)]] (process [, max_wait_time])
process: Shall be a type(process_type) object representing the external process to monitor.
This is an intent(inout) argument, and its state is updated upon completion.
max_wait_time (optional): Shall be a real value specifying the maximum wait time in seconds.
If not provided, the subroutine will wait indefinitely until the process completes.
{!example/system/example_process_2.f90!}Experimental
The update interface allows the internal state of a process object to be updated by querying the system.
After the process completes, the standard output and standard error are retrieved, if they were requested, and loaded into the process%stdout and process%stderr string variables, respectively.
This is especially useful for monitoring asynchronous processes and retrieving their output after they have finished.
call [[stdlib_subprocess(module):update(subroutine)]] (process)
process: Shall be a type(process_type) object representing the external process whose state needs to be updated.
This is an intent(inout) argument, and its internal state is updated on completion.
{!example/system/example_process_5.f90!}Experimental
The kill interface is used to terminate a running external process. It attempts to stop the process and returns a boolean flag indicating whether the operation was successful.
This interface is useful when a process needs to be forcefully stopped, for example, if it becomes unresponsive or if its execution is no longer required.
call [[stdlib_subprocess(module):kill(subroutine)]] (process, success)
process: Shall be a type(process_type) object representing the external process to be terminated.
This is an intent(inout) argument, and on return is updated with the terminated process state.
success: Shall be a logical variable. It is set to .true. if the process was successfully killed, or .false. otherwise.
{!example/system/example_process_4.f90!}Experimental
The sleep interface pauses the execution of a program for a specified duration, given in milliseconds.
This routine acts as a cross-platform wrapper, abstracting the underlying platform-specific sleep implementations.
It ensures that the requested sleep duration is honored on both Windows and Unix-like systems.
call [[stdlib_system(module):sleep(subroutine)]] (millisec)
millisec: Shall be an integer representing the number of milliseconds to sleep. This is an intent(in) argument.
{!example/system/example_sleep.f90!}Experimental
The is_windows interface provides a quick, compile-time check to determine if the current system is Windows.
It leverages a C function that checks for the presence of the _WIN32 macro, which is defined in C compilers when targeting Windows.
This function is highly efficient and works during the compilation phase, avoiding the need for runtime checks.
result = [[stdlib_system(module):is_windows(function)]] ()
Returns a logical flag: .true. if the system is Windows, or .false. otherwise.
{!example/system/example_process_1.f90!}Experimental
get_runtime_os inspects the runtime environment to identify the current OS type. It evaluates environment variables (OSTYPE, OS) and checks for specific files associated with known operating systems.
The supported OS types are integer, parameter variables stored in the stdlib_system module:
- Linux (
OS_LINUX) - macOS (
OS_MACOS) - Windows (
OS_WINDOWS) - Cygwin (
OS_CYGWIN) - Solaris (
OS_SOLARIS) - FreeBSD (
OS_FREEBSD) - OpenBSD (
OS_OPENBSD)
If the OS cannot be identified, the function returns OS_UNKNOWN.
os = [[stdlib_system(module):get_runtime_os(function)]]()
Function
None.
Returns one of the integer OS_* parameters representing the OS type, from the stdlib_system module, or OS_UNKNOWN if undetermined.
{!example/system/example_get_runtime_os.f90!}Experimental
OS_TYPE provides a cached result of the get_runtime_os function. The OS type is determined during the first invocation and stored in a static variable.
Subsequent calls reuse the cached value, making this function highly efficient.
This caching mechanism ensures negligible overhead for repeated calls, unlike get_runtime_os, which performs a full runtime inspection.
os = [[stdlib_system(module):OS_TYPE(function)]]()
Function
None.
Returns one of the integer OS_* parameters representing the OS type, from the stdlib_system module, or OS_UNKNOWN if undetermined.
{!example/system/example_os_type.f90!}Experimental
This function returns the file path of the null device, which is a special file used to discard any data written to it. It reads as an empty file. The null device's path varies by operating system:
- On Windows, the null device is represented as
NUL. - On UNIX-like systems (Linux, macOS), the null device is represented as
/dev/null.
path = [[stdlib_system(module):null_device(function)]]()
Function
None.
- Type:
character(:), allocatable - Returns the null device file path as a character string, appropriate for the operating system.
{!example/system/example_null_device.f90!}