02-05-2018
There's one big pitfall with this: Which program is reading when? It will be very easy to end up in a deadlock with both programs waiting for the other.
So, this is not nearly as simple as it appears, and why Expect is so valuable when it's really needed.
This User Gave Thanks to Corona688 For This Post:
10 More Discussions You Might Find Interesting
1. Programming
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:... (2 Replies)
Discussion started by: vvaidyan
2 Replies
2. UNIX for Dummies Questions & Answers
Hi,
i want to write a script that executes a program (exec?) .
this program then requires a filename as input.
how do i give it this input in the script so the program will be complete run and close by the script.
e.g.
exec prog.exe
program then asks for filename
"enter filename:"... (1 Reply)
Discussion started by: tuathan
1 Replies
3. Shell Programming and Scripting
Hi,
I would like to write a program to receive the GPS data and then send the data via network to other program.
All of the program is not write yet(include host and sender)
All of the server OS is unix or linux
Could you mind to give me some idea to do this?
Thanks so much!
Ken
... (2 Replies)
Discussion started by: kenlok
2 Replies
4. Solaris
Hello,
I recently upgraded our server from Solaris 8 to 9. The sendmail is unabled to pipe the email to a perl script. I can send and received email to local and external mail, but the script did not get the email. There is no error in the log and I could not find any thing on the web.
Here... (0 Replies)
Discussion started by: ld98
0 Replies
5. Programming
Hello guys,
my professor give me 2 days to study and make a program usign pipe, fork in c
i need to do a program
read a arq.txt
the father process read the file and the child print !
like this
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
int main (){
... (1 Reply)
Discussion started by: beandj
1 Replies
6. Homework & Coursework Questions
Hello guys,
my professor give me 2 days to study and make a program usign pipe, fork in c
i need to do a program
read a arq.txt
the father process read the file and the child print !
2. Relevant commands, code, scripts, algorithms:
like this
Code:
#include <stdio.h>... (1 Reply)
Discussion started by: beandj
1 Replies
7. UNIX for Advanced & Expert Users
Hi,
I am trying to sftp a large file(appx. 2 GB size) from solaris 10 to a Linux server. While sftping(with no options), connection is terminated after some time with broken pipe error. sftp with option -R1 or -B1500 is successful.
Linux server ssh Version: OpenSSH_3.9p1, OpenSSL 0.9.7a... (3 Replies)
Discussion started by: brij123
3 Replies
8. Linux
Hi all,
I have a text data file. My aim here is to find line called *FIELD* AV for every record and print lines after that till *FIELD* RF. But here I want first 3 to four lines for very record as well. FIELD AV is some where in between for very record. SO I am not sure how to retrieve lines in... (2 Replies)
Discussion started by: kaav06
2 Replies
9. Shell Programming and Scripting
For example, I have a file called number.txt.
x y
1 1
2 4
3 9
4 6
5 5
6 6
7 9
8 4
9 1
10 0
...
And I want to print out the value of x and y, if y%4==0 and the next value of y%4==0. Thus, the sample output is:
1 1 *because the previous x before 2 is 1
2 4 *because 4%4 == 0
7 9... (2 Replies)
Discussion started by: Tzeronone
2 Replies
10. Solaris
Hi Guys,
I am getting some strange error in /var/adm/messages in my Solaris 10 box with Veritas Cluster and EMC storage.
bash-3.00$ cat /var/adm/messages | egrep -v "lw8|snmp|sshd|xntpd|kern.info|LOGIN|link|service|started|finished|repeated|SS7 Log-daemon|success"
Dec 18 09:58:35 GAMMa2... (1 Reply)
Discussion started by: vivek.goel.piet
1 Replies
LEARN ABOUT CENTOS
ipc::open2
IPC::Open2(3pm) Perl Programmers Reference Guide IPC::Open2(3pm)
NAME
IPC::Open2 - open a process for both reading and writing using open2()
SYNOPSIS
use IPC::Open2;
$pid = open2(*CHLD_OUT, *CHLD_IN, 'some cmd and args');
# or without using the shell
$pid = open2(*CHLD_OUT, *CHLD_IN, 'some', 'cmd', 'and', 'args');
# or with handle autovivification
my($chld_out, $chld_in);
$pid = open2($chld_out, $chld_in, 'some cmd and args');
# or without using the shell
$pid = open2($chld_out, $chld_in, 'some', 'cmd', 'and', 'args');
waitpid( $pid, 0 );
my $child_exit_status = $? >> 8;
DESCRIPTION
The open2() function runs the given $cmd and connects $chld_out for reading and $chld_in for writing. It's what you think should work when
you try
$pid = open(HANDLE, "|cmd args|");
The write filehandle will have autoflush turned on.
If $chld_out is a string (that is, a bareword filehandle rather than a glob or a reference) and it begins with ">&", then the child will
send output directly to that file handle. If $chld_in is a string that begins with "<&", then $chld_in will be closed in the parent, and
the child will read from it directly. In both cases, there will be a dup(2) instead of a pipe(2) made.
If either reader or writer is the null string, this will be replaced by an autogenerated filehandle. If so, you must pass a valid lvalue
in the parameter slot so it can be overwritten in the caller, or an exception will be raised.
open2() returns the process ID of the child process. It doesn't return on failure: it just raises an exception matching "/^open2:/".
However, "exec" failures in the child are not detected. You'll have to trap SIGPIPE yourself.
open2() does not wait for and reap the child process after it exits. Except for short programs where it's acceptable to let the operating
system take care of this, you need to do this yourself. This is normally as simple as calling "waitpid $pid, 0" when you're done with the
process. Failing to do this can result in an accumulation of defunct or "zombie" processes. See "waitpid" in perlfunc for more
information.
This whole affair is quite dangerous, as you may block forever. It assumes it's going to talk to something like bc, both writing to it and
reading from it. This is presumably safe because you "know" that commands like bc will read a line at a time and output a line at a time.
Programs like sort that read their entire input stream first, however, are quite apt to cause deadlock.
The big problem with this approach is that if you don't have control over source code being run in the child process, you can't control
what it does with pipe buffering. Thus you can't just open a pipe to "cat -v" and continually read and write a line from it.
The IO::Pty and Expect modules from CPAN can help with this, as they provide a real tty (well, a pseudo-tty, actually), which gets you back
to line buffering in the invoked command again.
WARNING
The order of arguments differs from that of open3().
SEE ALSO
See IPC::Open3 for an alternative that handles STDERR as well. This function is really just a wrapper around open3().
perl v5.16.3 2013-03-04 IPC::Open2(3pm)