08-20-2012
Quote:
Originally Posted by
shyam.sunder91
thanks for ur reply i got an understanding over flushing buffers and their advantage
i did not get this line can u elucidate,what is getting connecting to tty device file
Back in the old days, when Teletype devices and stand-alone terminals were connected by wires to the back of a shared computer or over a phone line that was connected to a modem that was connected by wires to the back of a shared computer, everyone knew how a terminal appeared as a character special file that supported the general terminal interfaces.
Most vendor man page set will have a termios man page (but the section it is in will vary). Chapter 11 of the Base Definitions volume of the current POSIX standard has more than a dozen pages describing the General Terminal Interface (GTI).
The extremely quick overview, is that any time you have a user typing on a keyboard to interactively enter input into a program and interactively looking at output produced by a program on a screen or typewriter-like device, you are likely using a tty device or pseudo-tty device that behaves mostly as specified by the POSIX GTI.
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kill(2) System Calls Manual kill(2)
Name
kill - send signal to a process
Syntax
#include <sys/types.h>
#include <signal.h>
kill(pid, sig)
pid_t pid;
int sig;
Description
The system call sends the signal sig to a process specified by the process number pid. The sig can be a signal specified in a call or it
can be 0. If the sig is 0, error checking is performed, but a signal is not sent. This call can be used to check the validity of pid.
The sending and receiving processes must have the same effective user ID, otherwise this call is restricted to the superuser with the
exception of the signal SIGCONT. The signal SIGCONT can always be sent to a child or grandchild of the current process.
If the process number is 0, the signal is sent to all other processes in the sender's process group.
If the process number is negative but not -1, the signal is sent to all processes whose process-group-id is equal to the absolute value of
the process number.
The above two options are variants of
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process sending the signal.
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Environment
System Five
POSIX
When your program is compiled in the System V or POSIX environment, a signal is sent if either the real or effective uid of the sending
process matches the real or saved-set-uid (as described in ) of the receiving process. In addition, any process can use a pid of -1, and
the signal is sent to all processes subject to these permission checks.
In POSIX mode, the pid argument is of type pid_t.
Return Values
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned, and is set to indicate the error.
Diagnostics
The system call fails under the following conditions:
[EINVAL] The sig is not a valid signal number.
[EPERM] The sending process is not the superuser, and its effective user ID does not match the effective user ID of the receiving
process.
[ESRCH] No process can be found corresponding to that specified by pid.
See Also
execve(2), getpgrp(2), getpid(2), killpg(2), sigvec(2), pause(3)
kill(2)