Progress control of UNIX advanced programming

Process Control

PS aux
PS AXJ
PS AXF
PS AXM

I. Process identifiers
pid_t---->long int
Unique identity of the process

0 calling process (kernel)
1init process (user-state ancestor process for all processes)

Getpid (2);
Getppid (2);

Status of the process
s interruptible sleep state
R Run State
D Non-disruptive sleep state
T stop State
x termination state
Z Zombie State
Process priority
S conversation leader
L Multithreading
< high-priority
N Low-priority
+ in the foreground process group

Two. Fork (2)
Differences between parent and child processes:
<1>pid
<2>ppid
<3> Record Lock
<4> Resource usage and process time zeroing
<5> Pending signals
<6> Pending Alarms
<7>fork return value

Fork () Create child process
<1> cannot guarantee which process will run first
<2> using Copy-on-write
<3> returns the child process ID in the parent process, returning 0 in the child process

Vfork () Creating child processes
<1> ensure child processes run first
<2> Sharing parent process data segments and stacks
<3> terminating the process with _exit (2) or _exit (2)

Orphan process
Zombie Process

Three. Wait (2) and waitpid (2);

Wait (&status); = = Waitpid ( -1, &status, 0);

Four. EXEC (3);
Execl ();
Execv ();
EXECLP ();
EXECVP ();
Execle ();

Five.
Process relationships
1. Session: One or more process groups
GetSID (2);
Setsid (2);

2. Process group: One or more processes are composed of
GETPGRP (2);
Getpgid (2);
Setpgid (2);

Daemon process
Leader Pgid = = PID of the <1> process group
<2> session leader SID = = PID
<3> Disengagement Control Terminal

To create a daemon step:
<1>umask (0);
<2>chdir ("/");
<3> Close 0,1,2
<4>child-->setsid ();

Writing of log logs
Openlog ();
Syslog ();
Closelog ();

Daemon (3);

Six. Competitive conditions
Parent--->wait ();
Child--->getppid () = = 1

Seven. System (3)
Fork ()-->exec ("/bin/sh", "sh", "-C", "Ls-l", NULL)

Eight. Change the user ID and group ID
Actual User ID
Valid User id: Verify file Permissions U+s
Save Settings User ID

Setuid (2);
Getuid (2);
Geteuid (2);

Nine. Process time
Times (2);

Real: >= Sys+user;
Sys
User

10. Interpreter files
Know

Progress control of UNIX advanced programming