10-07-2011
@Corona Apologise if the bumping was excessive..
The fork is done as a part of the line, run the command in a subshell.
Thanks for the explanation though, let me ensure if I am correctly closing the ends of the pipe.
EDIT: Followup question though, is it necessary to use different pipes if there are more than 2 commands in my pipe?
Or can i reuse the same pipe?
say if I want to an ls | grep <pattern> | more.
Once ls is done with its task and grep done with the reading, the pipe would no longer be used right? so can the same be used between grep and more? [I think not..as grep would need access to 2 pipes simultaneously...one to read from and other to write to..in that case I need to address the correct file descriptors in my 2D array]
Last edited by ab_tall; 10-07-2011 at 02:25 PM..
10 More Discussions You Might Find Interesting
1. Filesystems, Disks and Memory
Hello!
How I can increase or decrease predefined pipe buffer size?
System FreeBSD 4.9 and RedHat Linux 9.0
Thanks! (1 Reply)
Discussion started by: Jus
1 Replies
2. Shell Programming and Scripting
Hi,
Can the cd command be invoked using pipes???
My actual question is slightly different. I am trying to run an executable from different folders and the path of these folders are obtained dynamically from the front end. Is there a way in which i can actually run the executable... (2 Replies)
Discussion started by: Sinbad
2 Replies
3. UNIX for Advanced & Expert Users
Hi...Can anyone please guide me on FIFO Pipes in UNIX.I have lerant things like creating fifo pipes,using them for reads and writes etc.I want to know what is the maximum amount of memory that such a pipe may have? Also can anyone guide me on where to get info on this topic from? (4 Replies)
Discussion started by: tej.buch
4 Replies
4. UNIX for Advanced & Expert Users
This is something I've given a lot of thought to and come up with no answer.
Say you have a data stream passing from a file, through process A, into process B. Process A only modifies a few bytes of the stream, then prints the rest of the stream unmodified. Is there any way to stream the file... (4 Replies)
Discussion started by: Corona688
4 Replies
5. Shell Programming and Scripting
How to have a conversation between 2 processes using named pipes? (5 Replies)
Discussion started by: kanchan_agr
5 Replies
6. UNIX for Dummies Questions & Answers
im trying to figure out how to do the following:
using pipes to combine grep and find commands to print all lines in files that start with the letter f in the current directory that contain the word "test" for example?
again using pipes to combine grep and find command, how can I print all... (1 Reply)
Discussion started by: ez45
1 Replies
7. Shell Programming and Scripting
I am really new to UNIX and programming in general and so apologies if this thread is a bit simple.
I have searched and found a piece of sample code for a training program I am currently undertaking, but seeing as I am relatively new, I dont completely understand how it works.
Here is the... (1 Reply)
Discussion started by: Makaer
1 Replies
8. UNIX for Dummies Questions & Answers
I am really new to UNIX and programming in general and so apologies if this thread is a bit simple.
I have searched and found a piece of sample code for a training program I am currently undertaking, but seeing as I am relatively new, I dont completely understand how it works.
Here is the... (6 Replies)
Discussion started by: Makaer
6 Replies
9. Programming
Hello all, I am trying to learn more about programming Unix pipes in C.
I have created a pipe that does od -bc < myfile | head
Now, I am trying to create od -bc < myfile | head | wc
Here is my code, and I know I might be off, thats why I am here so I can get some clarification.
#include... (1 Reply)
Discussion started by: petrca
1 Replies
10. Homework & Coursework Questions
Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!
1. The problem statement, all variables and given/known data:
Create a pipe to show the number of people who are logged into the system right now.
Create a pipe to show... (2 Replies)
Discussion started by: lakers34kb
2 Replies
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)