Between two binaries, one pipe can serve only one way communication. YOU need two pipes for to and fro communication. You need one pipe to write data to STDIN of another program (B) and need another pipe to read the STDOUT from that another program (B).
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:
---------... (1 Reply)
PROGRAM A <-> PROGRAM B
PROGRAM A sends data as STDIN ro PROGRAM B and when PROGRAM B is executed from PROGRAM A, it sends output back to PROGRAM A. This is implemented using 2 pipes (fd1 & fd2).
The above process happens in a loop and during the second run, the previous data that had been... (10 Replies)
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:
---------... (3 Replies)
Hi all
I've run into a snag in a program of mine where part of what I entered in at the start of run-time, instead of the current value within printf() is being printed out.
After failing with fflush() and setbuf(), I tried the following approach
void BufferFlusher()
{
int in=0;... (9 Replies)
When a process fork(), the child share the same file descriptors as his father. Thus, they share the same stdin. Quick and dirty exemple below (sorry for the ugly gets() call) :
#include <stdio.h>
#include <unistd.h>
int main()
{
char buf;
if (fork()) { /*parent */
... (1 Reply)
hello everybode.Got some sort of "problems" with this stuff;
well this is a program
int main()
{
int Pipe;
int origStdin, origStdout;
int childPID;
origStdin = dup(0);
origStdout = dup(1);
pipe(Pipe);
if( (childPID = fork()) < 0 )
{
perror(... (2 Replies)
Hi,
i am using the below program to read from the standard input or to write to standard out put.
i know that using highlevel functions this can be done better than what i have done here.
i just want to know is there any other method by which i find the exact number of characters ( this... (3 Replies)
Well.. let's say i need to write a pretty simple script.
In my script i have 2 variables which can have value of 0 or 1.
$VERBOSE
$LOG
I need to implement these cases:
($VERBOSE = 0 && $LOG = 0) => ONLY ERROR output (STDERR to console && STDOUT to /dev/null)
($VERBOSE = 1... (5 Replies)
Discussion started by: Marmz
5 Replies
LEARN ABOUT OPENDARWIN
pipe
PIPE(2) BSD System Calls Manual PIPE(2)NAME
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