Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Reading from blocking fifo pipe in shell script
Top Forums Shell Programming and Scripting Reading from blocking fifo pipe in shell script Post 302116663 by victorin on Monday 7th of May 2007 12:40:40 PM
Old 05-07-2007
Reading from blocking fifo pipe in shell script
Hi!!

I have a problem reading from a fifo pipe in shell script.

The idea is simple, I have a C program with two pipe files:
  • An input pipe I use to send commands in shell script to the C program (echo "command" > input.pipe)
  • An output pipe that I read the result of the command also in shell script (cat output.pipe)

The problem is in the cat output.pipe
After output the data the cat process remains blocked (like a "tail -f") waiting for data.

It's possible to avoid this state?? (It's possible the cat terminates when the pipe not contains more data? Something like non-blocking read)

Thank you very much
 

10 More Discussions You Might Find Interesting

1. Programming

Pipe & fifo....

Could someone Help me with this code please? #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <string.h> #include <fcntl.h> #define SIZE_B 256 /*buffer's size */ #define NUM_ARG 20 /* max number of args for any command */ int... (4 Replies)
Discussion started by: M3xican
4 Replies

2. UNIX for Advanced & Expert Users

PIPE and FIFO buffer size

Hello! How I can increase (or decrease) the predefined pipe buffer size? Thanks! (1 Reply)
Discussion started by: Jus
1 Replies

3. UNIX for Dummies Questions & Answers

fifo or named pipe working?

Can someone explain to me the working of fifo() system call using simple C programs so that I can implement them in the UNIX environement? (1 Reply)
Discussion started by: lvkchaitanya
1 Replies

4. Shell Programming and Scripting

Non-blocking pipe

Hello, Would this be an acceptable way of creating a non-blocking pipe. Basically I want to create kind of a server client arch. This code would be in the server, and I don't want to have to wait for clients to read before moving on to the next client. One problem I can see is if... (4 Replies)
Discussion started by: cdlaforc
4 Replies

5. UNIX for Advanced & Expert Users

Why not SIGPIPE for readers of pipe/FIFO?

Hi This is a exercise question from Unix network programming vol2. Why the SIGPIPE signal is generated only for writers when readers disappear. why not it is generated for readers when writer disappears. I guess, if the writer didn't get any response like the reader gets EOF, it will... (4 Replies)
Discussion started by: kumaran_5555
4 Replies

6. Homework & Coursework Questions

FIFO possible blocking or unknown error

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 chat program using two FIFOs one for writing and the other for reading. The problem is something... (1 Reply)
Discussion started by: Ebodee
1 Replies

7. Programming

Pipe & fifo size limit

Hi guys. 1. how much is the size of pipe?(i mean the buffer size) 2. is this size different in various UNIX derivations? 3. what happens if we write to a full pipe? does it block until get some free space(the other side receive data) or returns an error? 3. FIFO s are physical files on the... (2 Replies)
Discussion started by: majid.merkava
2 Replies

8. Shell Programming and Scripting

awk reading from named pipe (fifo)

I'm trying to read a fifo using awk and comming across some problems. I'm writing to the fifo from multiple processes invoked by GNU Parallel: mkfifo my_fifo awk '{ a = a + $2 } END { for (i in a) print i, a }' my_fifo | sort -nk1 > sorted_output grep -v '^@' massive_file | parallel... (3 Replies)
Discussion started by: nathanhaigh
3 Replies

9. Shell Programming and Scripting

Using Named pipe in shell script

Hi, I want to use a Named pipe to get input from a growing file for further processing. When I prototype this scenario using a while loop, the data is not written to the named pipe. This the script I use to get data into the Named pipe: #!/bin/ksh mkfifo pipe while (( n <= 10 )) do echo... (2 Replies)
Discussion started by: sudvishw
2 Replies

10. Shell Programming and Scripting

UNIX fifo concurrent read from a named pipe

I have created a fifo named pipe in solaris, which writes the content of a file, line by line, into pipe as below: $ mkfifo namepipe $ cat books.txt "how to write unix code" "how to write oracle code" $ cat books.txt >> namepipe & I have a readpipe.sh script which reads the named... (2 Replies)
Discussion started by: naveen mani
2 Replies

LEARN ABOUT OPENDARWIN

script

SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME

     script -- make typescript of terminal session

SYNOPSIS

     script [-a] [-k] [-q] [-t time] [file [command ...]]

DESCRIPTION

     The script utility makes a typescript of everything printed on your terminal.  It is useful for students who need a hardcopy record of an
     interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1).

     If the argument file is given, script saves all dialogue in file.	If no file name is given, the typescript is saved in the file typescript.

     If the argument command ... is given, script will run the specified command with an optional argument vector instead of an interactive shell.

     Options:

     -a       Append the output to file or typescript, retaining the prior contents.

     -k       Log keys sent to program as well as output.

     -q       Run in quiet mode, omit the start and stop status messages.

     -t time  Specify time interval between flushing script output file.  A value of 0 causes script to flush for every character I/O event.  The
	      default interval is 30 seconds.

     The script ends when the forked shell (or command) exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if
     ignoreeof is not set) for the C-shell, csh(1)).

     Certain interactive commands, such as vi(1), create garbage in the typescript file.  The script utility works best with commands that do not
     manipulate the screen.  The results are meant to emulate a hardcopy terminal, not an addressable one.

ENVIRONMENT

     The following environment variable is utilized by script:

     SHELL  If the variable SHELL exists, the shell forked by script will be that shell.  If SHELL is not set, the Bourne shell is assumed.  (Most
	    shells set this variable automatically).

SEE ALSO

     csh(1) (for the history mechanism).

HISTORY

     The script command appeared in 3.0BSD.

BUGS

     The script utility places everything in the log file, including linefeeds and backspaces.	This is not what the naive user expects.

     It is not possible to specify a command without also naming the script file because of argument parsing compatibility issues.

     When running in -k mode, echo cancelling is far from ideal.  The slave terminal mode is checked for ECHO mode to check when to avoid manual
     echo logging.  This does not work when in a raw mode where the program being run is doing manual echo.

BSD
								   June 6, 1993 							       BSD
All times are GMT -4. The time now is 11:14 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy