Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

pipe(2) [bsd man page]

PIPE(2) 							System Calls Manual							   PIPE(2)

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)

Check Out this Related Man Page

PIPE(2) 						      BSD System Calls Manual							   PIPE(2)

pipe -- create descriptor pair for interprocess communication SYNOPSIS
#include <unistd.h> int pipe(int *fildes); DESCRIPTION
The pipe() function creates a pipe, which is an object allowing unidirectional data flow, and allocates a pair of file descriptors. The first descriptor connects to the read end of the pipe, and the second connects to the write end, so that data written to fildes[1] appears on (i.e., can be read from) fildes[0]. This allows the output of one program to be sent to another program: the source's standard output is set up to be the write end of the pipe, and the sink's standard input is set up to be the read end of the pipe. The pipe itself persists until all its associated descriptors are closed. A pipe whose read or write end has been closed is considered widowed. Writing on such a pipe causes the writing process to receive a SIGPIPE signal. Widowing a pipe is the only way to deliver end-of-file to a reader: after the reader consumes any buffered data, reading a widowed pipe returns a zero count. RETURN VALUES
On successful creation of the pipe, zero is returned. Otherwise, a value of -1 is returned and the variable errno set to indicate the error. 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) HISTORY
A pipe() function call appeared in Version 6 AT&T UNIX. 4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution
Man Page

15 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers


if i want to pipe output to a file, say, cat abc.dat > abc.txt, how do i make it replace the existing file? (9 Replies)
Discussion started by: Duckman
9 Replies

2. UNIX for Advanced & Expert Users

Can't create more pipe

How can I change the maxnumber of pipes on my workstation? I'm running an EXPECT script that is suppose to start up 32 xterms. But after 18 opened xterm, I get this msg: - couldn't create pipe: too many open files regard, chris (9 Replies)
Discussion started by: uabcbac
9 Replies

3. HP-UX

remove named pipes

Hi, Please help me on this. I am creating a named pipe in a kshell script. I am using mkfifo pipe_name command to create the pipe. I want to remove the named pipe after my work is completed. How can i do that. (8 Replies)
Discussion started by: chintapalli001
8 Replies

4. Shell Programming and Scripting

Append line that does not contain pipe to it previous line

Hi All, I have a file which contains data as below When we see no pipe character in the line. append those lines to the previous line with pipe character till we get the next line with pipe character with ~(concat with ~) Input file looks like: 1080530944|001|john.l.bonner|Acknowledge|CN... (11 Replies)
Discussion started by: ainuddin
11 Replies

5. Shell Programming and Scripting

Subsitute from a position till end of line.

Hi, Having a following file's content, lets say: ABC|ANA|LDJ|||||DKD|||||| AJJ|KKDD||KKDK|||||||||||| KKD||KD|||LLLD||||LLD||||| Problem: Need to replace pipes from 8th occurrence of pipe till end. so the result should be: ABC|ANA|LDJ|||||DKD AJJ|KKDD||KKDK|||| ------- ------- ... (12 Replies)
Discussion started by: _Noprofi
12 Replies

6. Shell Programming and Scripting

grep functions, how to test if succeeded

Hello ...again. I am stuck on this part, I have a loop with processes an operations file. and calls different functions depending on what is in loop, which processes a database file... #so far my add function works as intended add() { ...blah blah; } # delete is kinda working... (13 Replies)
Discussion started by: gcampton
13 Replies

7. Shell Programming and Scripting

Replace blanks with | (pipe)

Hello, I'm trying to replace the first x number of spaces in a line with a |. Right now I'm using a very inefficient syntax to accomplish the task and was looking to simplify it. I have several cases were the pipes need to replace just the first space on the line, which I did a simple... (11 Replies)
Discussion started by: bd_joy
11 Replies

8. Shell Programming and Scripting

Awk to Search and Replace inside the pipe "|"

Hi, Anyone can help me on how to replace the qoutes inside the pipe | in my Text File like belows; "AAAA"|"Test "1-A""|"Test AAAA"|"This is A" "BBBB"|"Test "1-B""|"Test BBBB"|"This is B" "CCCC"|"My Test C"|"Test "CCCC""|"This is C" The output I need like belows; "AAAA"|"Test 1-A"|"Test... (12 Replies)
Discussion started by: fspalero
12 Replies

9. Homework & Coursework Questions

While loop...

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: I am trying to read a file that was made using VI that consists of a user login name, full name, phone number and... (15 Replies)
Discussion started by: csharp100
15 Replies

10. UNIX for Advanced & Expert Users

write failed: Broken pipe

The "write failed: Broken pipe" message is reported by the file sending PC which run my writed network device driver while 500MB or 900MB is sended! What does the message mean? Does this mean there is a bug in my driver? li,kunlun (11 Replies)
Discussion started by: liklstar
11 Replies

11. Shell Programming and Scripting

Process file every minute

Hey guy's, How can I schedule this script using AWK, what I require is it runs every minute as new data will be added to the file? And I need to capture these data and save it to the output file. I tried using sleep 1 to allow the file to be processed but is not working. awk ' ... (35 Replies)
Discussion started by: James_Owen
35 Replies

12. Shell Programming and Scripting

Reading data from file using awk

I have a file as below. It contains two data sets separated by >. I want to pipe each data set to another program called psxy. How can I get the different records Have started doing as follows but it only passes the first data set awk 'BEGIN {RS=">"};{print $0}' p.dat cat p.dat... (12 Replies)
Discussion started by: kristinu
12 Replies

13. Shell Programming and Scripting

To remove duplicates from pipe delimited file

Hi some one please help me to remove duplicates from a pipe delimited file based on first two columns. 123|asdf|sfsd|qwrer 431|yui|qwer|opws 123|asdf|pol|njio Here My first record and last record are duplicates.As per my requirement I want all the latest records into one file. I want the... (12 Replies)
Discussion started by: ginrkf
12 Replies

14. Shell Programming and Scripting

Would pipe work better with this command

Hi again, have a script that I would like run, but before I can run it I need to strip out the windows \r end of lines. I have put the command into a text file and set the command to run every 10 seconds the coomand I use to do this is while sleep 10; do... (15 Replies)
Discussion started by: Paul Walker
15 Replies

15. Shell Programming and Scripting

Ksh: run commands from pipe

I create commands within a pipe and finally want them to be executed instead of being displayed on the screen. What is the last stage in this pipe? I found by guessing that "ksh" is working, but is this the best to use here? It boils down to this: echo "print Hello World!"| kshWhat is the... (15 Replies)
Discussion started by: Cochise
15 Replies