Dear all,
If I login to a Unix system (general user account), will the unix system generate a history file?
If positve, will it stored the IP adress also?
Thanks and Regards
Penny Li
;) (2 Replies)
Hello all,
I'm ufs file system, how can u use the same disk in another machine with the data in tact? to make it clear, I've an ufs FS in a mount point /file1 ( 8GB). now they decide to reintall the OS. After the reinstall, how can i get the same data as it is? will mounting the disk as /file1... (3 Replies)
Hello all !
Could someone throw some light on whether there's a limit to the number of characters contained in the command string that is passed to the system() call in C.
Is it OS dependent? If yes, what are the limits for each?
Thanks. (4 Replies)
Hello,
I have few questions about file system in Unix and Linux.
1. What's the difference between Unix and Linux in their file system? Are they the same?
2. Is in Unix directory for administrator "/root" - like in Linux - Ubuntu or not?
3.Where is the users directory in Unix? Is it... (2 Replies)
in man system it talks about SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
Does this signal stuff also happen in popen command?
(even though man popen says nothing about signals)
also if I am not using wait(&status) and I am using waitpid(pid, NULL, 0)
how would... (1 Reply)
Hi
I have created a perl script & running it using Linux machine. I want my script to die when system command is unsuccessful but script is dying even when system command gets executed successfully. :wall:
I am using the command below :-
system($cmd) || die "FAILED $!";
print "Hello";
... (2 Replies)
I'm currently studying for my exam, and is practicing with sample exam questions.
However there is a question asking "Name THREE UNIX Directory system calls" and the answer given is "opendir, closedir and readdir", however the next question ask "Why is a write directory system call not included... (1 Reply)
Hi,
The file system unix use a multilevel indexes access to disk, 12 direct blocks, 1 single indirect block, 1 double indirect block, 1 triple indirect block:
Assuming a:
block = 512 bytes,
pointer = 4 byte,
and there is a file of 200 blocks,
how many disk access is needed to read the block... (1 Reply)
Hi,
I am on Solaris 10 server which is running Veritas. It's E420 server with two drives. I don't know much about Veritas. The other guy who works on this, on vacation this week. :-) Any way, looks like I have hard drive issue on the server.
When I do iostat -E. I see this.
sd0... (4 Replies)
Discussion started by: samnyc
4 Replies
LEARN ABOUT SUSE
pipe
PIPE(2) Linux Programmer's Manual PIPE(2)NAME
pipe, pipe2 - create pipe
SYNOPSIS
#include <unistd.h>
int pipe(int pipefd[2]);
#define _GNU_SOURCE
#include <unistd.h>
int pipe2(int pipefd[2], int flags);
DESCRIPTION
pipe() creates a pipe, a unidirectional data channel that can be used for interprocess communication. The array pipefd is used to return
two file descriptors referring to the ends of the pipe. pipefd[0] refers to the read end of the pipe. pipefd[1] refers to the write end
of the pipe. Data written to the write end of the pipe is buffered by the kernel until it is read from the read end of the pipe. For fur-
ther details, see pipe(7).
If flags is 0, then pipe2() is the same as pipe(). The following values can be bitwise ORed in flags to obtain different behavior:
O_NONBLOCK Set the O_NONBLOCK file status flag on the two new open file descriptions. Using this flag saves extra calls to fcntl(2) to
achieve the same result.
O_CLOEXEC Set the close-on-exec (FD_CLOEXEC) flag on the two new file descriptors. See the description of the same flag in open(2) for
reasons why this may be useful.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORS
EFAULT pipefd is not valid.
EINVAL (pipe2()) Invalid value in flags.
EMFILE Too many file descriptors are in use by the process.
ENFILE The system limit on the total number of open files has been reached.
VERSIONS
pipe2() was added to Linux in version 2.6.27; glibc support is available starting with version 2.9.
CONFORMING TO
pipe(): POSIX.1-2001.
pipe2() is Linux-specific.
EXAMPLE
The following program creates a pipe, and then fork(2)s to create a child process; the child inherits a duplicate set of file descriptors
that refer to the same pipe. After the fork(2), each process closes the descriptors that it doesn't need for the pipe (see pipe(7)). The
parent then writes the string contained in the program's command-line argument to the pipe, and the child reads this string a byte at a
time from the pipe and echoes it on standard output.
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int
main(int argc, char *argv[])
{
int pipefd[2];
pid_t cpid;
char buf;
if (argc != 2) {
fprintf(stderr, "Usage: %s <string>
", argv[0]);
exit(EXIT_FAILURE);
}
if (pipe(pipefd) == -1) {
perror("pipe");
exit(EXIT_FAILURE);
}
cpid = fork();
if (cpid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (cpid == 0) { /* Child reads from pipe */
close(pipefd[1]); /* Close unused write end */
while (read(pipefd[0], &buf, 1) > 0)
write(STDOUT_FILENO, &buf, 1);
write(STDOUT_FILENO, "
", 1);
close(pipefd[0]);
_exit(EXIT_SUCCESS);
} else { /* Parent writes argv[1] to pipe */
close(pipefd[0]); /* Close unused read end */
write(pipefd[1], argv[1], strlen(argv[1]));
close(pipefd[1]); /* Reader will see EOF */
wait(NULL); /* Wait for child */
exit(EXIT_SUCCESS);
}
}
SEE ALSO fork(2), read(2), socketpair(2), write(2), popen(3), pipe(7)COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2009-09-15 PIPE(2)