I can't tell for sure without reading the code, but my guess would be that the pipe is blocking, waiting for a newline.
You can set the pipe to nonblocking with:
Code:
#include <unistd.h>
#include <fcntl.h>
...
// Create pipe
pipe(pvals);
// Set both ends of pipe to nonblocking
for(n=0; n<2; n++)
{
// Get previous flags
int f = fcntl(pvals[n], F_GETFL, 0);
// Set bit for non-blocking flag
f |= O_NONBLOCK;
// Change flags on fd
fcntl(pvals[n], F_SETFL, f);
}
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)
I know how to read and write if i have a forked process with only one child. However what is involved with reading and writing with many forked processes. Say one parent that forks 5 children, and needs to communicate with all 5 in half duplex.
int temp, counter=0;
do{
pipe(temp);
... (5 Replies)
I have the following code which works on AIX 4.3 but fails at times on AIX 5.3
with:
cat: 0652-054 cannot write to output. There is no process to read data written to a pipe.
validator="${validator_exe} ${validator_parms}"
cmd_line="${CAT} ${data_file} | ${validator}... (6 Replies)
Hi Everyone,
The machine I'm working on is an AIX 5.3 LPAR running on a P650. oslevel -r shows 5300-08. I'm trying to take a backup to a SCSI tape drive, which has been working up until this point. I know of nothing that has changed recently to cause this problem. But when I try to take a... (0 Replies)
I have a perl program that I want to read from a file passed as an argument or from a pipe. If their is no pipe or arguments, I want it to output a help message. I am stuck on how to prevent perl from reading from the keyboard if it isn't fed any file names or data from a pipe. The only things I... (4 Replies)
We use SAP application cluster on AIX. Communication between 2 of its instances is failing randomly with the following error:
java.net.SocketException: There is no process to read data written to a pipe.
The above error causes a cluster restart if an important communication fails.
Can... (0 Replies)
I have a file data_1.out which contains:
1|abc mail|mail subject|mail body
2|def mail|mail subject|def mail body
I am trying to read the variables from data_1.out and use them to print to 2 different files based on the id (first_column)
The problem is I am not able to read the file... (8 Replies)
Hello,
I need to read the pipe data as:-
cat abc.txt | uuencode abc.txt | mailx -s hi xyz@xyz.com
I will override the mailx function so that when mailx is called, it calls my version of maix and in that function I want to read the file which is attached in progional mailx function- abc.txt... (7 Replies)
Hello,
I have an ffmpeg bash script which is working nice and
I need to do the same for other sources.
To create new scripts and to deal with multiple bash files sounds not logical. It is a bit hard to manage for me..
I wondered if it was possible to make my input file as variable.
Then I... (1 Reply)
Hi All,
I'm creating a program which reads millions of bytes from the PIPE and do some processing. As the data is more, the idea is to read the pipe parallely.
Sun Solaris 8
See the code below:
#!/bin/sh
MAXTHREAD=30
awk '{print $1}' metadata.csv > nvpipe &
while
do
... (3 Replies)
Discussion started by: mr_manii
3 Replies
LEARN ABOUT BSD
pipe
PIPE(2) System Calls Manual PIPE(2)NAME
pipe - create an interprocess communication channel
SYNOPSIS
pipe(fildes)
int fildes[2];
DESCRIPTION
The pipe system call creates an I/O mechanism called a pipe. The file descriptors returned can be used in read and write operations. When
the pipe is written using the descriptor fildes[1] up to 4096 bytes of data are buffered before the writing process is suspended. A read
using the descriptor fildes[0] will pick up the data.
It is assumed that after the pipe has been set up, two (or more) cooperating processes (created by subsequent fork calls) will pass data
through the pipe with read and write calls.
The shell has a syntax to set up a linear array of processes connected by pipes.
Read calls on an empty pipe (no buffered data) with only one end (all write file descriptors closed) returns an end-of-file.
Pipes are really a special case of the socketpair(2) call and, in fact, are implemented as such in the system.
A signal is generated if a write on a pipe with only one end is attempted.
RETURN VALUE
The function value zero is returned if the pipe was created; -1 if an error occurred.
ERRORS
The pipe call will fail if:
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
[EFAULT] The fildes buffer is in an invalid area of the process's address space.
SEE ALSO sh(1), read(2), write(2), fork(2), socketpair(2)BUGS
Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock will occur.
4th Berkeley Distribution August 26, 1985 PIPE(2)