I have encountered a strange problem dealing with pipes
and forking. The program basicaly does this:
cat file | tbl | eqn | groff
Now, I have a parent process that forks children
that that exec the stuff that they should. The pipes defined
in the parent are the ones used.
The chain goes... (1 Reply)
I use read often in scripts to filter the right part into a variable like:
$ print "abc cde efg" | read k l ; print "k=$k, l=$l"
k=, l=
This works on linux and unix versions I work with. On OSX 10.4 this
doesn't work. I found a workaround but would like to know
why the original line... (5 Replies)
Basically I am trying to write a short script to report total space used on /u0? file systems. This is what I was trying to do:df -k /u0? | grep -v kbytes | awk '{ printf $2 "+" }' | sed s/.$// | bcBut it returns no output.
This works however: > A=`df -k /u0? |grep -v kbytes | awk '{ printf $2... (2 Replies)
Is there a way to know whether is pipe is opened in read or write mode.I mean is there any signal that is generated when a pipe is opened in read or write mode.
If you have some solution .please let me know ........ (2 Replies)
Hi,
Can any one please help me with this. Am struggling hard to get a solution.
I am doing telnet through a C program and getting the stdout file descriptor of the remote machine to pipe.
read() function is getting data, But whenl it receives SOH character ie. ^A ( Start of heading = Console... (2 Replies)
Could anyone tell me whats wrong whit this piping? the commands that they execute are correct. the command I am trying is ls|wc. Both processes go to the right if statement.
for(i=0;i<argc;i++){
if(i==0&&argc>1){//first command
if(pipe(pipa1)==-1)
... (2 Replies)
Hello !
I want to process a text file in order to extract desired data using sed and grep... Now I am facing a problem piping to grep... nothing happens..
The text consists of blocks of 3 lines that may (or not) contain the Desired data.
the desired data is on each 2... (4 Replies)
hi i am having issues with extra pipe.
i have a data file and i need to remove the extra pipe in the(example 4th and 7thline) in datafile. there are many other line and filed like this which i need to remove from files. The sample data is below:
270 31|455004|24/03/2010|0001235|72
271... (3 Replies)
Hi,guys:
I want to use c to implement a pipe. For example:
ps auxwww | grep fred | more
I forked three child processes. Each is responsible for each command, and pipe to next one.
for(i=0;i<2;i++)
pipe(fd)
if(child==1) // child 1
{
close(1)
dup2(fd,1)
close(fd)
}... (3 Replies)
Hi!
I'm having problems with pipes... I need comunnications with childs processes and parents, but only one child can comunnicate with parent (first child), others childs can't.
A brief of code:
if(pipe(client1r)<0){
perror("pipe");
}
... (1 Reply)
Discussion started by: serpens11
1 Replies
LEARN ABOUT SUSE
tee
TEE(2) Linux Programmer's Manual TEE(2)NAME
tee - duplicating pipe content
SYNOPSIS
#define _GNU_SOURCE
#include <fcntl.h>
ssize_t tee(int fd_in, int fd_out, size_t len, unsigned int flags);
DESCRIPTION
tee() duplicates up to len bytes of data from the pipe referred to by the file descriptor fd_in to the pipe referred to by the file
descriptor fd_out. It does not consume the data that is duplicated from fd_in; therefore, that data can be copied by a subsequent
splice(2).
flags is a series of modifier flags, which share the name space with splice(2) and vmsplice(2):
SPLICE_F_MOVE Currently has no effect for tee(); see splice(2).
SPLICE_F_NONBLOCK Do not block on I/O; see splice(2) for further details.
SPLICE_F_MORE Currently has no effect for tee(), but may be implemented in the future; see splice(2).
SPLICE_F_GIFT Unused for tee(); see vmsplice(2).
RETURN VALUE
Upon successful completion, tee() returns the number of bytes that were duplicated between the input and output. A return value of 0 means
that there was no data to transfer, and it would not make sense to block, because there are no writers connected to the write end of the
pipe referred to by fd_in.
On error, tee() returns -1 and errno is set to indicate the error.
ERRORS
EINVAL fd_in or fd_out does not refer to a pipe; or fd_in and fd_out refer to the same pipe.
ENOMEM Out of memory.
VERSIONS
The tee() system call first appeared in Linux 2.6.17.
CONFORMING TO
This system call is Linux-specific.
NOTES
Conceptually, tee() copies the data between the two pipes. In reality no real data copying takes place though: under the covers, tee()
assigns data in the output by merely grabbing a reference to the input.
EXAMPLE
The following example implements a basic tee(1) program using the tee() system call.
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <limits.h>
int
main(int argc, char *argv[])
{
int fd;
int len, slen;
if (argc != 2) {
fprintf(stderr, "Usage: %s <file>
", argv[0]);
exit(EXIT_FAILURE);
}
fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
if (fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
do {
/*
* tee stdin to stdout.
*/
len = tee(STDIN_FILENO, STDOUT_FILENO,
INT_MAX, SPLICE_F_NONBLOCK);
if (len < 0) {
if (errno == EAGAIN)
continue;
perror("tee");
exit(EXIT_FAILURE);
} else
if (len == 0)
break;
/*
* Consume stdin by splicing it to a file.
*/
while (len > 0) {
slen = splice(STDIN_FILENO, NULL, fd, NULL,
len, SPLICE_F_MOVE);
if (slen < 0) {
perror("splice");
break;
}
len -= slen;
}
} while (1);
close(fd);
exit(EXIT_SUCCESS);
}
SEE ALSO splice(2), vmsplice(2), feature_test_macros(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 TEE(2)