the first element is the read end, the second element is the write end of the pipe.
On some platforms(Solaris) pipes are bidirectional, but this is classical UNIX.
Also, you need to reap (with some form of wait) all the pids you get back from fork, not just the last one, else you end up with zombies, so I would expect you to capture all those pids.
I have a simple script that I want to run every 30 minutes but only when I execute it. I don't want it to be a crontab job.
so i have for example
date
ls -l
who
sleep 1800
The first time it executes correctly but after the first time it nevers execute back again. It should execute after... (2 Replies)
Anyone have an idea why this if statement does not work correctly?
"test2.sh" 18 lines, 386 characters
#!/usr/bin/sh
WARNING=80
CRITICAL=95
check_it()
{
if ] || ];then
echo "YES ] || ]"
else
echo "NO ] || ]"
fi
}
check_it 80.1
check_it 81.1 (3 Replies)
Hi,
I have a script where I am trying to set a local variable using the following,
MYVAR="$NAME"_"$NAME2".txt
where say,
NAME = one
NAME2 = two
so I want the output one_two.txt but what I am getting is,
two.txt
basically the $NAME2 is overwriting, what am I doing wrong?
... (3 Replies)
egrep -A 7 -m 2 -h 'Date:|Time:' *.html
this is showing only 2 line after the context of the 2nd found match. Is this a bug in grep?
egrep -A 7 -m 2 -h 'Time:' *.html - this works correctly (2 Replies)
I am trying to copy 2 types of files so I can archive them. I tested with a set of commands:
touch -t $(date -d "-60 day" +%Y%m%d) WORKDIR/REF
find TARGETDIR/ -type f -maxdepth 1 -iname \*.out\* -or -iname \*.log\* ! -newer WORKDIR/REF -exec ls -l {} \;
This correctly lists any files in the... (2 Replies)
We are using Red Hat linux system.
I am transferring my rman backup files to another server.
Here is the command i am using to transfer the files.
/usr/bin/rsync -avpP --delete /xyz/xyz/ 99.99.999.99::db110bkp
Here is the rsync version.
>rsync --version
rsync version 3.0.6 ... (1 Reply)
Consider the following code:
grep -o -e '^STEAM_::\d+$' workfile3.tmp
A sample format of a valid string for the regexp would be:
STEAM_0:1:12345678
Here is an example line from the workfile3.tmp file:
465:L 01/02/2012 - 00:05:33: "Spartan1-1-7<8><STEAM_0:1:47539638><>" connected
No... (2 Replies)
Hi
I am attempting to right a script which will read a table and extract specfic information.
LASTFAILEDJOB=/usr/openv/netbackup/scripts/GB-LDN/Junaid/temp_files/lastfailedjob
cat /usr/openv/netbackup/scripts/GB-LDN/Junaid/temp_files/lastfailedjob
237308646
If i run the following... (5 Replies)
Hello All,
Yesterday, all day, I was using x11vnc and vncviewer to connect to a server. But today for some reason it is not working. I don't
remember changing any settings or anything like that, but because it stopped working correctly I guess something has...?
I'm issuing the exact same... (0 Replies)
Today I saw the topic. sum-even-numbers-1-100 At that time, it was already closed but not the point. Other thoughts came to mind.
All newcomers to Haskell are afraid that when they study it, their brains will turn inside out. I did not notice anything like that. And all because the brains of all... (4 Replies)
Discussion started by: nezabudka
4 Replies
LEARN ABOUT V7
pipe
PIPE(2) System Calls Manual PIPE(2)NAME
pipe - create an interprocess 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. Writes with a count of 4096 bytes or less are atomic; no other process can inter-
sperse 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.
SEE ALSO sh(1), read(2), write(2), fork(2)DIAGNOSTICS
The function value zero is returned if the pipe was created; -1 if too many files are already open. A signal is generated if a write on a
pipe with only one end is attempted.
BUGS
Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock will occur.
ASSEMBLER
(pipe = 42.)
sys pipe
(read file descriptor in r0)
(write file descriptor in r1)
PIPE(2)