If the filename begins with '|' , the filename is interpreted as a command to which output is to be piped, and if the filename ends with a '|' , the filename is interpreted as a command which pipes output to us. See "Using open() for IPC" in perlipc for more examples of this. (You are not allowed to open to a command that pipes both in and out, but see IPC::Open2, IPC::Open3, and "Bidirectional Communication with Another Process" in perlipc for alternatives.)
For three or more arguments if MODE is '|-' , the filename is interpreted as a command to which output is to be piped, and if MODE is '-|' , the filename is interpreted as a command which pipes output to us. In the 2-arguments (and 1-argument) form one should replace dash ('-' ) with the command. See "Using open() for IPC" in perlipc for more examples of this. (You are not allowed to open to a command that pipes both in and out, but see IPC::Open2, IPC::Open3, and "Bidirectional Communication" in perlipc for alternatives.)
So what you need would be something like (untested, needs error checking)
Can this be done without using te system command? I have a directory with a large number of files in it, but I am interested in only the 8 most recent.
The directory looks like
-rw-rw-rw- 1 adsm adsm 13412 Sep 22 08:31 events_dump_09222005.csv.gz
-rw-rw-rw- 1 adsm adsm ... (5 Replies)
Hi,
I'm wanting to run an nslookup, dig or whatever to check for the existence of a printer. The PERL script will display the results on the screen, but I can't figure out how to capture the result & test the value. Any ideas will be greatly appreciated!!! Thank You (1 Reply)
I am new to scripting in Perl so I have a dumb question.
I know I can call system commands using
system("date");
But I am not able to:
1. set its output to a variable
2. run in quiet mode(no output to the screen)
The examples i have
#!/usr/bin/perl
print `date +\%y\%m\%d.\%H\%M`;... (5 Replies)
Hi guys,
got a problem with a perl cgi script over here. I need it to run a system command to get the status of a process. Unfortunately the process is owned by a specific user and only this user can get its status. So i tried running the command from the perl cgi with "su", but then i get the... (12 Replies)
HI all,
can anyone tell me what does exit status 9 from perl's system function meant.
I am using system fuction to execute a shell script as :
my $s=system ('script.sh' ,arg1 ,arg2);
print $s;
the output is 9.
Thanks in advance. !!:confused: (1 Reply)
Hi ,
Is there any way to achieve following using perl program (i.e without using system command).
1.system ("echo 'test' > /usr/spool/ship.csv");
2.system ("cat /usr/ajay_test* >> /usr/spool/RAM/work/patil.csv");
3.system("> /usr/spool/ajay.txt");
e.g
for system("rm -f... (1 Reply)
Hello experts,
I have a perl script which looks for the ARGV and then loads the data as per it.
Example.
#Checking the server to connect
if ($ARGV eq 'QA')
{
$ENV{"ORACLE_HOME"} = "/oracle/product/11.2.0";
$ENV{"PATH"} = "$ENV{'PATH'}:/oracle/product/11.2.0/bin";
... (1 Reply)
Hi Guys,
Please help me.. it is urgent. I am writing a perl script to capture command output and redirect it to a logfile.At the same i want to check the return code of the command and log it if the command is not succesful in my logfile.. Here is my code, it is working but system command inside... (2 Replies)
Hi
I have script to collect file system usage statistics from few remote unix hosts and email . On the UNIX system the column spacing is fine but the email output is not aligned properly. Any tips to fix this ? (1 Reply)
Discussion started by: new2prog
1 Replies
LEARN ABOUT MOJAVE
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 v5.18.2 2013-11-04 IPC::Open2(3pm)