msh_jobs.cpp File Reference

Job control related utilities. More...

Functions
void	init_job_control ()
	Initialize job control.
void	sigchld_handler (int)
	SIGCHLD handler.
int	wait_for_process (pid_t pid, int *status)
	Wait for the process to finish.
int	reap_children ()
	Wait for all background processes to finish.
int	no_background_processes ()
	Return the number of currently running background processes.
void	print_processes ()
	Print all internal processes.
void	remove_completed_processes ()
	Remove all completed processes, i.e. whose status is DONE from the internal process table.
void	print_completed_processes ()
	Print all completed background processes.
void	update_jobs ()
	Update the internal process table.
void	add_process (pid_t pid, int flags, const std::vector< std::string > &args)
	Add a process to the internal process table.
void	remove_process (pid_t pid)
	Remove a process from the internal process table.
void	set_process_status (pid_t pid, status_t status)
	Change the status of a process in the internal process table.

Variables
std::map< pid_t, process >	processes
	The internal process table.

Detailed Description

Job control related utilities.

Simplest job control implementation. Just for demonstration purposes. Features only process tracking and printing.

MAYBE: In future implement full job control supporting foreground and background processes with respecting process groups and signals handling process pipelines.

Function Documentation

add_process()

void add_process	(	pid_t	pid,
		int	flags,
		const std::vector< std::string > &	args )

Add a process to the internal process table.

Parameters

pid	The process ID.
flags	The process flags.
args	The process arguments.

See also

process()

init_job_control()

void init_job_control

(

)

Initialize job control.

Set SIGCHLD handler.

See also

sigchld_handler()

no_background_processes()

int no_background_processes

(

)

Return the number of currently running background processes.

Returns

The number of currently running background processes.

print_completed_processes()

void print_completed_processes

(

)

Print all completed background processes.

Note

Only prints processes that were started asynchronously.

reap_children()

int reap_children

(

)

Wait for all background processes to finish.

Returns

The number of reaped processes.

Note

All processes reaped by this function are immediately removed from the internal process table.

See also

remove_process()

remove_process()

void remove_process

(

pid_t

pid

)

Remove a process from the internal process table.

Parameters

pid	The process ID.

set_process_status()

void set_process_status	(	pid_t	pid,
		status_t	status )

Change the status of a process in the internal process table.

Parameters

pid	The process ID.
status	The new process status.

sigchld_handler()

void sigchld_handler

(

int

)

SIGCHLD handler.

Reaps the process and updates its internal status.

See also

waitpid()

set_process_status()

Parameters

signo

The signal number.

update_jobs()

void update_jobs

(

)

Update the internal process table.

Is exactly equivalent to calling print_completed_processes() and remove_completed_processes() sequentially.

Note

This function should be called before every command execution.

See also

print_completed_processes()

remove_completed_processes()

wait_for_process()

int wait_for_process	(	pid_t	pid,
		int *	status )

Wait for the process to finish.

Parameters

pid	The process ID.
status	The process status.

Returns

The process exit status.

Note

Call to this function leads to explicit removal of the process with matching PID from the internal process table.

If both WIFEXITED and WIFSIGNALED are false for the process, the return value is undefined.

See also

remove_process()

Variable Documentation

processes

std::map<pid_t, process> processes

The internal process table.

Maps process IDs to process objects.