Category Operating System Functions

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Operating System Functions

The built-in statements and functions below work in every program. The std/os module adds Args( ) that keeps empty arguments, GetEnv that tells an unset variable from an empty one, host facts such as CpuCount( ), and Ctrl-C handling; std/process runs other programs with their arguments passed exactly, no shell in between, and pipes to their input and output.

Grouped by task. Operating system lists them beside the rest of the area.

Read the command line

Function	What it does	From
Command	Returns command-line argument n, the program's name for 0, or all of them if omitted.	built-in
Args	Returns every command-line argument as Unicode text, the program first, empty ones kept.	std/os

Run another program

Function	What it does	From
Shell	Runs a command through the system shell, waits, and returns its exit code or -1.	built-in
Exec	Runs a program by its path with arguments, waits, and returns its exit code or -1.	built-in
Chain	Runs a program without arguments, waits, and returns its exit code or -1.	built-in
Run	Hands control to another program and ends this one; returns -1 if it cannot start.	built-in
Command (std/process)	Holds a program and its arguments, passed exactly as given with no shell in between.	std/process
Run (std/process)	Runs a Command with this program's console, waits, and returns its exit status.	std/process
Capture	Runs a Command, waits, and returns its exit status and all it wrote to stdout and stderr.	std/process
Shell (std/process)	Runs a command line through cmd.exe or /bin/sh, waits, and returns its exit status.	std/process

Set up a program's arguments, folder and pipes

Function	What it does	From
Command.Arg	Adds one argument and returns the Command, so calls chain.	std/process
Command.Args	Adds every string in an Array as an argument.	std/process
Command.Cwd	Sets the folder the program starts in.	std/process
Command.Env	Sets one environment variable for the program only.	std/process
Command.EnvRemove	Removes one environment variable for the program only.	std/process
Command.EnvClear	Starts the program with an empty environment, which Env calls then add to.	std/process
Command.StdinFrom / StdoutTo / StderrTo	Connects the program's stdin, stdout or stderr to this console, to nothing, or to a pipe.	std/process
Command.StderrToStdout	Sends the program's stderr wherever its stdout goes.	std/process
Command.NewProcessGroup	Starts the program in its own process group, so Windows can send it Ctrl-Break.	std/process
Command.HideWindow	Starts a console program on Windows without opening a console window.	std/process
Command.ToString	Returns the command line quoted as the system will see it, for logs.	std/process
Stdio	Names where a stream goes: STDIO_INHERIT, STDIO_NULL or STDIO_PIPE.	std/process

Talk to a program while it runs

Function	What it does	From
Child	Holds one running program; destroying it leaves the program running.	std/process
Child.Spawn	Starts the program a Command describes, or returns why it could not.	std/process
Child.Id	Returns the running program's process id.	std/process
Child.Stdin / Stdout / Stderr	Returns the pipe to the program's stdin, stdout or stderr when the Command asked for one.	std/process
Child.Wait	Closes the program's stdin, waits for it to end, and returns its exit status.	std/process
Child.WaitTimeout	Waits up to a number of milliseconds; returns the exit status, or none if still running.	std/process
Child.TryWait	Returns the exit status if the program has ended, or none if it is still running.	std/process
Child.Kill	Ends the program at once.	std/process
Child.Terminate	Asks the program to stop; on Windows it ends it at once, as Kill does.	std/process
PipeStream	Holds one end of a pipe to a program, read and written like any other stream.	std/process

Read a program's exit code and output

Function	What it does	From
ExitStatus	Holds how a program ended: its exit code and, on Linux and macOS, the ending signal.	std/process
ExitStatus.Code	Returns the program's exit code, or -1 on Linux and macOS when a signal ended it.	std/process
ExitStatus.Success	Returns true if the exit code is 0.	std/process
ExitStatus.Signal	Returns the signal that ended the program on Linux and macOS, or 0.	std/process
ProcessOutput	Holds a finished program's exit status and the bytes it wrote to stdout and stderr.	std/process
ProcessOutput.StdoutText / StderrText	Returns what the program wrote as UTF-8 text, with U+FFFD for any bad bytes.	std/process

Read and set environment variables

Function	What it does	From
Environ	Returns the value of an environment variable, or an empty string if it is not set.	built-in
SetEnviron	Sets an environment variable from "NAME=value" text; returns 0 on success.	built-in
GetEnv	Returns an environment variable's value, or an empty Optional when it is not set.	std/os
SetEnv	Sets an environment variable for this program and the programs it starts.	std/os
UnsetEnv	Removes an environment variable; removing one that is not set succeeds.	std/os
Environment	Returns every environment variable as a map of names to values, sorted by name.	std/os
ExpandEnv	Replaces $NAME and ${NAME} in text, and %NAME% on Windows, with the variables' values.	std/os

Catch Ctrl-C and stop cleanly

Function	What it does	From
CatchInterrupt	Turns Ctrl-C, Ctrl-Break and requests to stop into a flag, instead of ending the program.	std/os
Interrupted	Returns true once an interrupt has arrived; never waits.	std/os
WaitInterrupt	Waits for an interrupt and returns true, or false if the time runs out first.	std/os
LastInterrupt	Returns which kind of interrupt arrived, such as INT_CTRL_C, or INT_NONE.	std/os
InterruptCount	Returns how many interrupts have arrived since the last reset.	std/os
ResetInterrupt	Clears the interrupt flag and the count.	std/os
ReleaseInterrupt	Gives Ctrl-C and the other signals back to their default handling.	std/os
InterruptKind	Names the kinds of interrupt: Ctrl-C, Ctrl-Break, terminate and hang-up.	std/os
InterruptContext	Returns a Context cancelled by the first interrupt, so goroutines stop on Ctrl-C.	std/tasks

Find out about the computer and this program

Function	What it does	From
OS_NAME	Holds "windows", "linux" or "macos", the system the program was built for.	std/os
ARCH_NAME	Holds "x86_64", the processor the program was built for.	std/os
OsVersion	Returns the Windows version number, or the kernel release on Linux and macOS.	std/os
Hostname	Returns the computer's network name, or an error.	std/os
UserName	Returns the name of the user running the program, or an error.	std/os
ProcessId	Returns this program's process id.	std/os
CurrentId	Returns this program's process id, the same number as ProcessId.	std/process
CpuCount	Returns how many processors this program may run on, which can be fewer than exist.	std/os
PageSize	Returns the memory page size in bytes.	std/os
TotalMemory	Returns the computer's physical memory in bytes, or 0 if it cannot be found.	std/os
IsTerminal	Returns true if stdin, stdout or stderr is an interactive terminal.	std/os

Find the program's folder and the current folder

Function	What it does	From
ExePath	Returns the folder that holds the running program.	built-in
CurDir	Returns the current folder.	built-in
ChDir	Changes the current folder; returns 0 on success or -1 on failure.	built-in

Make, remove and list folders

Function	What it does	From
MkDir	Creates one folder, whose parent must already exist; returns 0 on success.	built-in
RmDir	Removes an empty folder; returns 0 on success or -1 on failure.	built-in
Dir	Returns the first name matching a pattern, then the next one on each later call.	built-in

Copy, rename and delete files

Function	What it does	From
FileCopy	Copies a file, overwriting the destination; returns 0 on success.	file.bi
Name	Renames or moves a file or folder; returns 0 on success.	built-in
Kill	Deletes a file; returns 0 on success or an error code.	built-in

Check whether a file exists, its size and date

Function	What it does	From
FileExists	Returns non-zero if the file exists, or 0 if it does not.	file.bi
FileLen	Returns the size of a named file in bytes.	file.bi
FileDateTime	Returns when a file was last modified, as a date serial.	file.bi

Work with an open file number

Function	What it does	From
FileAttr	Returns an open file number's mode, system handle or encoding.	file.bi
FileFlush	Writes buffered output for one or all open files to the system, or on to disk.	file.bi
FileSetEof	Cuts or extends an open file so that it ends at the current position.	file.bi

End the program

Function	What it does	From
System	Closes all open files and ends the program, with an optional exit code.	built-in
ExitWith	Ends the program with an exit code, running module destructors and flushing files.	std/os
Abort	Ends the program at once, with no cleanup at all.	std/os

Check free memory and redirection

Function	What it does	From
Fre	Returns the amount of free physical memory, in bytes.	built-in
IsRedirected	Returns non-zero if standard output, or input if asked, is redirected to a file.	fbio.bi

Find out why a call failed

Function	What it does	From
OsError	Holds why a std/os call failed: a code, the system's error number and a message.	std/os
OsErrorMessage	Returns the message text for a std/os error code, such as "invalid argument".	std/os
ProcError	Holds why a program could not be started or waited for: a code, a number, a message.	std/process
ProcErrorMessage	Returns the message text for a std/process error code, such as "program not found".	std/process

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