A fifo works pretty much like a pipe....
In both cases one process reads and the other process writes. This brings up the main difference, with modern pipes, it is possible to move data in both directions...but this is seldom done. A fifo is unidirectional only.
Hi All
L2000-44
HP-UX 11.00
I am attempting to setup a FIFO over NFS. Directing and reading from the FIFO works fine on the local machine - however when I direct to the FIFO from a server which has the directory NFS mounted it does not work. The a process to read from the FIFO on the local... (2 Replies)
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)
Hi ,
I m beginner for Unix and i want to use FIFO in my 2 Scripts . I want 1 script to read data from FIFO and other will write into FIFO.
Despite reading so many articles/posts i am still unable sunchronize my scripts.
My doubts are
1> Do We require both scripts as daemons to use... (0 Replies)
Hello,
I have a FIFO which i would like to open O_WDWR | O_NONBLOCK | O_ASYNC and have a SIGIO signal generated when there is input on the FIFO, but there a re a bunch of bugs surrounding this (like for instance i read somewhere that you have to set O_ASYNC with fcntl etc.
is this even... (0 Replies)
hi, my problem is
i have 10 thread for produces double two dimensional array these will produces 2d array 400 times ,then i have a thread to takes a two dimensional array then it inverse , and most 10 array can be in the fifo , and threads given takes one by one, now my problem is , i cant... (0 Replies)
Hello C programming fellows!!!
I'm doing a program with multiple threads in gnu/linux, ubuntu for beeing precise...
This program consist in multiple threads, as logical each thread do different things and communicate to each other using IPC.
The problem is that in "process 1" I have a... (1 Reply)
Dear friends
i'm want to implement a program which one file is split into fragments by the server (by some random size) and sent to some processes, so these processes get randomly the fragments of the original file from the server, then the downloader randomly connects to some of these processes... (0 Replies)
Hello ,
I am working on unix FIFO IPC. i have a doubt regarding that.
If the fifo is updated(write()) through one process....can we able to send any signal that fifo is updated and ready to get read...to other process.?? (0 Replies)
Hi all,
First of all, sorry for the pastebin link. The code tags aren't working for me.
#!/bin/bash # while-menu-dialog: a menu driven - Pastebin.com
This is a channel "changer" shell script i'm working on. It uses dialog to display the menus.
It... (3 Replies)
Discussion started by: ignatius
3 Replies
LEARN ABOUT REDHAT
popen
POPEN(3) Linux Programmer's Manual POPEN(3)NAME
popen, pclose - process I/O
SYNOPSIS
#include <stdio.h>
FILE *popen(const char *command, const char *type);
int pclose(FILE *stream);
DESCRIPTION
The popen() function opens a process by creating a pipe, forking, and invoking the shell. Since a pipe is by definition unidirectional,
the type argument may specify only reading or writing, not both; the resulting stream is correspondingly read-only or write-only.
The command argument is a pointer to a null-terminated string containing a shell command line. This command is passed to /bin/sh using the
-c flag; interpretation, if any, is performed by the shell. The mode argument is a pointer to a null-terminated string which must be
either `r' for reading or `w' for writing.
The return value from popen() is a normal standard I/O stream in all respects save that it must be closed with pclose() rather than
fclose(). Writing to such a stream writes to the standard input of the command; the command's standard output is the same as that of the
process that called popen(), unless this is altered by the command itself. Conversely, reading from a ``popened'' stream reads the com-
mand's standard output, and the command's standard input is the same as that of the process that called popen.
Note that output popen streams are fully buffered by default.
The pclose function waits for the associated process to terminate and returns the exit status of the command as returned by wait4.
RETURN VALUE
The popen function returns NULL if the fork(2) or pipe(2) calls fail, or if it cannot allocate memory.
The pclose function returns -1 if wait4 returns an error, or some other error is detected.
ERRORS
The popen function does not set errno if memory allocation fails. If the underlying fork() or pipe() fails, errno is set appropriately.
If the mode argument is invalid, and this condition is detected, errno is set to EINVAL.
If pclose() cannot obtain the child status, errno is set to ECHILD.
CONFORMING TO
POSIX.2
BUGS
Since the standard input of a command opened for reading shares its seek offset with the process that called popen(), if the original
process has done a buffered read, the command's input position may not be as expected. Similarly, the output from a command opened for
writing may become intermingled with that of the original process. The latter can be avoided by calling fflush(3) before popen.
Failure to execute the shell is indistinguishable from the shell's failure to execute command, or an immediate exit of the command. The
only hint is an exit status of 127.
HISTORY
A popen() and a pclose() function appeared in Version 7 AT&T UNIX.
SEE ALSO fork(2), sh(1), pipe(2), wait4(2), fflush(3), fclose(3), fopen(3), stdio(3), system(3)BSD MANPAGE 1998-05-07 POPEN(3)