IPC via named pipe: Difference between revisions
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{{draft task}}
[[wp:Named pipe|Named pipe]], or FIFO, is a way of providing inter-process communications (IPC). The
# Data written to the "in" FIFO will be discarded except the byte count, which will be added to a total tally kept by the program;
# Whenever another process reads the "out" FIFO, it should receive the total count so far.
Possible issues:
* Chances are you don't already have "in" and "out" pipes lying around. Create them within your program or without, at your discretion. You may assume they are already created for you.
* Your program may assume it's the sole reader on "in" and the sole writer on "out".
* Read/write
* You may assume other processes using the pipes behave; specificially, your program may assume the process at the other end of a pipe will not unexpectedly break away before you finish reading or writing.
=={{header|C}}==
{{libheader|pthread}}
<syntaxhighlight lang="c">#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <pthread.h>
/* Flag for systems where a blocking open on a pipe will block
entire process instead of just current thread. Ideally this
kind of flags should be automatically probed, but not before
we are sure about how each OS behaves. It can be set to 1
even if not needed to, but that would force polling, which I'd
rather not do.
Linux: won't block all threads (0)
OpenBSD: will block all (1)
Other OSes: ?
*/
#define WILL_BLOCK_EVERYTHING 0
#if WILL_BLOCK_EVERYTHING
#include <poll.h>
#endif
size_t tally = 0;
void* write_loop(void *a)
{
int fd;
char buf[32];
while (1) {
#if WILL_BLOCK_EVERYTHING
/* try to open non-block. sleep and retry if no reader */
fd = open("out", O_WRONLY|O_NONBLOCK);
if (fd < 0) { /* assume it's ENXIO, "no reader" */
usleep(200000);
continue;
}
#else
/* block open, until a reader comes along */
fd = open("out", O_WRONLY);
#endif
write(fd, buf, snprintf(buf, 32, "%d\n", tally));
close(fd);
/* Give the reader a chance to go away. We yeild, OS signals
reader end of input, reader leaves. If a new reader comes
along while we sleep, it will block wait. */
usleep(10000);
}
}
void read_loop()
{
int fd;
size_t len;
char buf[PIPE_BUF];
#if WILL_BLOCK_EVERYTHING
struct pollfd pfd;
pfd.events = POLLIN;
#endif
while (1) {
#if WILL_BLOCK_EVERYTHING
fd = pfd.fd = open("in", O_RDONLY|O_NONBLOCK);
fcntl(fd, F_SETFL, 0); /* disable O_NONBLOCK */
poll(&pfd, 1, INFTIM); /* poll to avoid reading EOF */
#else
fd = open("in", O_RDONLY);
#endif
while ((len = read(fd, buf, PIPE_BUF)) > 0) tally += len;
close(fd);
}
}
int main()
{
pthread_t pid;
/* haphazardly create the fifos. It's ok if the fifos already exist,
but things won't work out if the files exist but are not fifos;
if we don't have write permission; if we are on NFS; etc. Just
pretend it works. */
mkfifo("in", 0666);
mkfifo("out", 0666);
/* because of blocking on open O_WRONLY, can't select */
pthread_create(&pid, 0, write_loop, 0);
read_loop();
return 0;
}</syntaxhighlight>
=={{header|FreeBASIC}}==
<syntaxhighlight lang="vbnet">#Include "file.bi"
Type FileInfo
As String path
As Integer oflag
End Type
Function OpenFile(file As FileInfo) As Integer
Dim As Integer f = Freefile
Open file.path For Binary Access Read Write As #f
If Lof(f) > 0 Then
Print "Error opening file"
Return -1
End If
Return f
End Function
Function ReadFromFile(f As Integer, Byref buf As String, size As Integer) As Integer
Get #f, , buf
Return Len(buf)
End Function
Sub WriteToFile(f As Integer, buf As String, size As Integer)
Put #f, , buf
End Sub
Dim As FileInfo inputFile
inputFile.path = "in.fifo"
inputFile.oflag = 0
Dim As FileInfo outputFile
outputFile.path = "out.fifo"
outputFile.oflag = 1
Dim As Integer entrada = OpenFile(inputFile)
Dim As Integer salida = OpenFile(outputFile)
If entrada = -1 Or salida = -1 Then
Print "Error opening files"
End
End If
Dim As String buffer
Dim As Integer bytesRead
Do
bytesRead = ReadFromFile(entrada, buffer, 64)
If bytesRead > 0 Then WriteToFile(salida, buffer, bytesRead)
Loop</syntaxhighlight>
=={{header|Go}}==
<syntaxhighlight lang="go">package main
import (
"fmt"
"io"
"log"
"os"
"sync/atomic"
"syscall"
)
const (
inputFifo = "/tmp/in.fifo"
outputFifo = "/tmp/out.fifo"
readsize = 64 << 10
)
func openFifo(path string, oflag int) (f *os.File, err error) {
err = syscall.Mkfifo(path, 0660)
// We'll ignore "file exists" errors and assume the FIFO was pre-made
if err != nil && !os.IsExist(err) {
return
}
f, err = os.OpenFile(path, oflag, 0660)
if err != nil {
return
}
// In case we're using a pre-made file, check that it's actually a FIFO
fi, err := f.Stat()
if err != nil {
f.Close()
return nil, err
}
if fi.Mode()&os.ModeType != os.ModeNamedPipe {
f.Close()
return nil, os.ErrExist
}
return
}
func main() {
var byteCount int64
go func() {
var delta int
var err error
buf := make([]byte, readsize)
for {
input, err := openFifo(inputFifo, os.O_RDONLY)
if err != nil {
break
}
for err == nil {
delta, err = input.Read(buf)
atomic.AddInt64(&byteCount, int64(delta))
}
input.Close()
if err != io.EOF {
break
}
}
log.Fatal(err)
}()
for {
output, err := openFifo(outputFifo, os.O_WRONLY)
if err != nil {
log.Fatal(err)
}
cnt := atomic.LoadInt64(&byteCount)
fmt.Fprintln(output, cnt)
output.Close()
}
}</syntaxhighlight>
=={{header|Perl}}==
{{trans|Raku}}
<syntaxhighlight lang="perl"># 20200924 added Perl programming solution
use strict;
use warnings;
use File::Temp qw/ :POSIX /;
use POSIX qw/ mkfifo /;
use Fcntl;
my ($in, $out) = map { scalar tmpnam() } 0,1 ;
for ($in, $out) { mkfifo($_,0666) or die $! };
print "In pipe : $in\nOut pipe : $out\n";
my $CharCount = 0 ;
$SIG{INT} = sub {
for ($in, $out) { unlink $_ or die }
print "\nTotal Character Count: $CharCount\nBye.\n" and exit
};
sysopen( IN, $in, O_NONBLOCK|O_RDONLY ) or die;
sysopen( OUT, $out, O_NONBLOCK|O_RDWR ) or die;
while (1) {
sysread(IN, my $buf, 32); # borrowed the buffer size from the c entry
if ( length $buf > 0 ) {
$CharCount += length $buf;
while (sysread(OUT, $buf, 1)) {} ; # empty the write pipe
syswrite( OUT, $CharCount ) or die;
}
sleep .5;
}</syntaxhighlight>
{{out}}
Terminal 1
<pre>In pipe : /tmp/0oPaYmkOI2
Out pipe : /tmp/DdWOGVOaBI
^C
Total Character Count: 7083641
Bye.</pre>
Terminal 2
<pre>echo asdf > /tmp/0oPaYmkOI2
cat /tmp/DdWOGVOaBI
5^C
echo qwer > /tmp/0oPaYmkOI2
echo uiop > /tmp/0oPaYmkOI2
cat /tmp/DdWOGVOaBI
15^C
wc /etc/passwd
33 63 1642 /etc/passwd
cat /etc/passwd > /tmp/0oPaYmkOI2
cat /tmp/DdWOGVOaBI
1657^C
cat /dev/urandom > /tmp/0oPaYmkOI2
^C
cat /tmp/DdWOGVOaBI
7083641^C</pre>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #000080;font-style:italic;">--
-- demo\rosetta\IPC_via_named_pipe.exw
-- ===================================
--
-- Note: uses a single bidirectional pipe, Windows only, and no attempt has been
-- made to avoid blocking, this sort of code should be put in a separate thread.
--
-- Running normally starts this as a server which automatically creates a client.
--
-- Several additional Windows-only routines have been added to builtins/pipeio.e
-- which will not be formally documented until they are fully Linux-compatible.
--</span>
<span style="color: #7060A8;">requires</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"1.0.1"</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">requires</span><span style="color: #0000FF;">(</span><span style="color: #004600;">WINDOWS</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">without</span> <span style="color: #008080;">js</span> <span style="color: #000080;font-style:italic;">-- (obviously this will never ever run in a browser!)</span>
<span style="color: #008080;">include</span> <span style="color: #000000;">builtins</span><span style="color: #0000FF;">/</span><span style="color: #000000;">pipeio</span><span style="color: #0000FF;">.</span><span style="color: #000000;">e</span>
<span style="color: #008080;">constant</span> <span style="color: #000000;">szPipename</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">`\\.\pipe\mynamedpipe`</span><span style="color: #0000FF;">,</span>
<span style="color: #000000;">cl</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">command_line</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">rand_string</span><span style="color: #0000FF;">()</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">repeat</span><span style="color: #0000FF;">(</span><span style="color: #008000;">' '</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">rand</span><span style="color: #0000FF;">(</span><span style="color: #000000;">100</span><span style="color: #0000FF;">))</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">res</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">res</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">rand_range</span><span style="color: #0000FF;">(</span><span style="color: #008000;">'A'</span><span style="color: #0000FF;">,</span><span style="color: #008000;">'Z'</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">res</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"-client"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cl</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Server\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">dwPipeMode</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">or_all</span><span style="color: #0000FF;">({</span><span style="color: #000000;">PIPE_TYPE_MESSAGE</span><span style="color: #0000FF;">,</span><span style="color: #000000;">PIPE_READMODE_MESSAGE</span><span style="color: #0000FF;">,</span><span style="color: #000000;">PIPE_WAIT</span><span style="color: #0000FF;">}),</span>
<span style="color: #000000;">totalsofar</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #004080;">atom</span> <span style="color: #000000;">pBuffer</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">allocate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1024</span><span style="color: #0000FF;">),</span>
<span style="color: #000000;">pBytesRead</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">allocate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">4</span><span style="color: #0000FF;">),</span>
<span style="color: #000000;">pBytesWritten</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">allocate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">4</span><span style="color: #0000FF;">),</span>
<span style="color: #000000;">hPipe</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">create_named_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">szPipename</span><span style="color: #0000FF;">,</span><span style="color: #000000;">PIPE_ACCESS_DUPLEX</span><span style="color: #0000FF;">,</span><span style="color: #000000;">dwPipeMode</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">{}</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">system_exec</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">(</span><span style="color: #008000;">`"%s" "%s" -client`</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cl</span><span style="color: #0000FF;">),</span><span style="color: #000000;">8</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">while</span> <span style="color: #004600;">true</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">connect_named_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">res</span><span style="color: #0000FF;">></span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #0000FF;">?</span><span style="color: #000000;">9</span><span style="color: #0000FF;">/</span><span style="color: #000000;">0</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">read_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">,</span><span style="color: #000000;">pBuffer</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1024</span><span style="color: #0000FF;">,</span><span style="color: #000000;">pBytesRead</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #000000;">res</span> <span style="color: #008080;">then</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"\nsleep??\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">sleep</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0.25</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">else</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">bytesread</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">peek4s</span><span style="color: #0000FF;">(</span><span style="color: #000000;">pBytesRead</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">msg</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">peek</span><span style="color: #0000FF;">({</span><span style="color: #000000;">pBuffer</span><span style="color: #0000FF;">,</span><span style="color: #000000;">bytesread</span><span style="color: #0000FF;">})</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">bytesread</span><span style="color: #0000FF;">=</span><span style="color: #000000;">4</span> <span style="color: #008080;">and</span> <span style="color: #000000;">msg</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"quit"</span> <span style="color: #008080;">then</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"\nquit recieved, quitting\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">exit</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">totalsofar</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">bytesread</span>
<span style="color: #7060A8;">progress</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"bytesread:%,d total so far:%,d "</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">bytesread</span><span style="color: #0000FF;">,</span><span style="color: #000000;">totalsofar</span><span style="color: #0000FF;">})</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">reply</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"%,d"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">totalsofar</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">write_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">,</span><span style="color: #000000;">reply</span><span style="color: #0000FF;">,</span><span style="color: #000000;">pBytesWritten</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #000000;">res</span> <span style="color: #008080;">or</span> <span style="color: #7060A8;">peek4s</span><span style="color: #0000FF;">(</span><span style="color: #000000;">pBytesWritten</span><span style="color: #0000FF;">)!=</span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">reply</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #0000FF;">?</span><span style="color: #000000;">9</span><span style="color: #0000FF;">/</span><span style="color: #000000;">0</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">flush_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">disconnect_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #7060A8;">free</span><span style="color: #0000FF;">({</span><span style="color: #000000;">pBytesWritten</span><span style="color: #0000FF;">,</span><span style="color: #000000;">pBuffer</span><span style="color: #0000FF;">,</span><span style="color: #000000;">pBytesRead</span><span style="color: #0000FF;">})</span>
<span style="color: #000000;">close_handle</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hPipe</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">else</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Client\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Press Escape or Q to quit\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">running_total</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #008080;">while</span> <span style="color: #008080;">not</span> <span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">get_key</span><span style="color: #0000FF;">(),{</span><span style="color: #008000;">'q'</span><span style="color: #0000FF;">,</span><span style="color: #008000;">'Q'</span><span style="color: #0000FF;">,</span><span style="color: #000000;">#1B</span><span style="color: #0000FF;">})</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">msg</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">rand_string</span><span style="color: #0000FF;">(),</span>
<span style="color: #000000;">reply</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">call_named_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">szPipename</span><span style="color: #0000FF;">,</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">running_total</span> <span style="color: #0000FF;">+=</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">bool</span> <span style="color: #000000;">bOK</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">reply</span><span style="color: #0000FF;">==</span><span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"%,d"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">running_total</span><span style="color: #0000FF;">))</span>
<span style="color: #7060A8;">progress</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"set %d bytes, reply:%s, running_total:%,d (same:%t)"</span><span style="color: #0000FF;">,</span>
<span style="color: #0000FF;">{</span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">),</span> <span style="color: #000000;">reply</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">running_total</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">bOK</span><span style="color: #0000FF;">})</span>
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #000000;">bOK</span> <span style="color: #008080;">then</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"\nsome error, quitting...\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">exit</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #0000FF;">{}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">call_named_pipe</span><span style="color: #0000FF;">(</span><span style="color: #000000;">szPipename</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"quit"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<!--</syntaxhighlight>-->
{{out}}
After letting it run for about 5s before hitting escape, on separate terminal windows:
<pre>
Server
bytesread:19 total so far:2,136,798
quit recieved, quitting
Client
Press Escape or Q to quit
set 19 bytes, reply:2,136,798, running_total:2,136,798 (same:true)
</pre>
=={{header|PicoLisp}}==
<syntaxhighlight lang="picolisp">(call 'mkfifo "in" "out") # Create pipes
(zero *Cnt) # Initialize byte counter
(unless (fork) # Handle "out" pipe
(loop
(out "out"
(sync)
(tell)
(prinl *Cnt) ) ) )
(unless (fork) # Handle "in" pipe
(let P (open "in")
(loop
(in P # Open twice, to avoid broken pipes
(while (rd 1) # (works on Linux, perhaps not POSIX)
(tell 'inc ''*Cnt) ) ) ) ) )
(push '*Bye '(call 'rm "in" "out")) # Remove pipes upon exit
(wait) # (Terminate with Ctrl-C)</syntaxhighlight>
Test:
<pre>$ line <out
0
$ echo abc >in
$ line <out
4
$ echo äöü >in
$ line <out
11</pre>
=={{header|Racket}}==
<syntaxhighlight lang="racket">#lang racket
(define-values (in out) (make-pipe))
;; Thread loops through list of strings to send
;; and closes port when finished
(define t1 (thread (lambda ()
(for ([i (list "a" "test" "sequence")])
(display i out)
(sleep 1))
(close-output-port out))))
;; Blocking call to read char, if not EOF then loop
(define t2 (thread (lambda ()
(define cnt 0)
(let loop ()
(when (not (eof-object? (read-char in)))
(set! cnt (add1 cnt))
(loop)))
(display (format "Bytes Rx: ~a\n" cnt))
(close-input-port in))))
(thread-wait t1)
(thread-wait t2)</syntaxhighlight>
=={{header|Raku}}==
{{incorrect|Raku| Blocks on the read pipe and not able to empty/update the write pipe according to the task requirement }}
Couldn't figure out how to get around the IO blockages as per the talk page so any help would be appreciated, thanks in advance.
<syntaxhighlight lang="raku" line># 20200923 Added Raku programming solution
use NativeCall;
use UUID; # cannot mix File::Temp with mkfifo well so use this as tmpnam
my ($in, $out) = <in out>.map: { "/tmp/$_-" ~ UUID.new } ;
sub mkfifo(Str $pathname, int32 $mode --> int32) is native('libc.so.6') is symbol('mkfifo') {*}
($in,$out).map: { die $!.message if mkfifo($_, 0o666) } ; # c style exit code
say "In pipe: ", $in;
say "Out pipe: ", $out;
my atomicint $CharCount = 0;
signal(SIGINT).tap: {
($in,$out).map: { .IO.unlink or die } ;
say "\nBye." and exit;
}
loop {
given $in.IO.watch { # always true even when nothing is spinning ?
say "Current count: ", $CharCount ⚛+= $in.IO.open.readchars.codes;
given $out.IO.open(:update :truncate) { # both truncate and flush aren't
.flush or die ; # working on pipes so without a
.spurt: "$CharCount\t" # prior consumer it just appends
}
$out.IO.open.close or die;
}
sleep ½;
}</syntaxhighlight>
{{out}}
Terminal 1
<pre>named-pipe.raku
In pipe: /tmp/in-b49e4cdf-80b6-49da-b4a3-2810f1eeeb6a
Out pipe: /tmp/out-44fcd0db-ce02-47b4-bdd3-34833f3dd621
Current count: 5
Current count: 10
Current count: 15
^C
Bye.</pre>
Terminal 2
<pre>echo asdf > /tmp/in-b49e4cdf-80b6-49da-b4a3-2810f1eeeb6a
cat /tmp/out-44fcd0db-ce02-47b4-bdd3-34833f3dd621
5 ^C
echo qwer > /tmp/in-b49e4cdf-80b6-49da-b4a3-2810f1eeeb6a
echo uiop > /tmp/in-b49e4cdf-80b6-49da-b4a3-2810f1eeeb6a
cat /tmp/out-44fcd0db-ce02-47b4-bdd3-34833f3dd621
10 15 ^C</pre>
=={{header|Ruby}}==
{{improve|Ruby|
* Find a way to report errors from inside ''open_sesame'', such as Errno::ENOENT.
* Check that open file is a FIFO: <code>foopipe.stat.pipe?</code>
}}
With [[OpenBSD]], we observe that open(2) a named pipe blocks ''all threads'' in a process. (This must be bug in thread library.) So, we fork(2) other process to call open(2), and apply UNIXSocket to send IO object.
{{works with|Unix}}
<syntaxhighlight lang="ruby">require 'socket'
# Ruby has no direct access to mkfifo(2). We use a shell script.
system '/bin/sh', '-c', <<EOF or abort
test -p in || mkfifo in || exit
test -p out || mkfifo out || exit
EOF
# Forks a process to open _path_. Returns a _socket_ to receive the open
# IO object (by UNIXSocket#recv_io).
def open_sesame(path, mode)
reader, writer = UNIXSocket.pair
pid = fork do
begin
reader.close
file = File.open(path, mode)
writer.send_io file
ensure
exit!
end
end
Process.detach pid
writer.close
return reader
end
insock = open_sesame("in", "rb")
outsock = open_sesame("out", "w")
inpipe, outpipe = nil
count = 0
readers = [insock, outsock]
writers = []
loop do
selection = select(readers, writers)
selection[0].each do |reader|
case reader
when insock
inpipe = insock.recv_io
puts "-- Opened 'in' pipe."
insock.close
readers.delete insock
readers.push inpipe
when outsock
outpipe = outsock.recv_io
puts "-- Opened 'out' pipe."
outsock.close
readers.delete outsock
writers.push outpipe
when inpipe
count += (inpipe.read_nonblock(4096).size rescue 0)
end
end
selection[1].each do |writer|
case writer
when outpipe
outpipe.puts count
puts "-- Counted #{count} bytes."
exit
end
end
end</syntaxhighlight>
Example run:
{| class="wikitable"
| style="vertical-align: top; width: 50%;" | <pre>$ ruby count.rb
-- Opened 'in' pipe.
-- Opened 'out' pipe.
-- Counted 32 bytes.
$</pre>
| style="vertical-align: top; width: 50%;" | <pre>$ echo 'This is line 1.' > in
$ echo 'This is line 2.' > in
$ cat out
32
$</pre>
|}
=={{header|Tcl}}==
<syntaxhighlight lang="tcl"># Make the pipes by calling a subprocess...
exec sh -c {test -p in || mkfifo in || exit 1;test -p out || exec mkfifo out}
# How many bytes have we seen so far?
set count 0
# Read side; uses standard fileevent mechanism (select() under the covers)
set in [open in {RDONLY NONBLOCK}]
fconfigure $in -translation binary
fileevent $in readable consume
proc consume {} {
global count in
# Reads only 4kB at a time
set data [read $in 4096]
incr count [string length $data]
}
# Writer side; relies on open() throwing ENXIO on non-blocking open of write side
proc reportEveryHalfSecond {} {
global count
catch {
set out [open out {WRONLY NONBLOCK}]
puts $out $count
close $out
}
# Polling nastiness!
after 500 reportEveryHalfSecond
}
reportEveryHalfSecond
# Run the event loop until done
vwait forever</syntaxhighlight>
=={{header|Wren}}==
{{trans|C}}
{{libheader|pthread}}
An embedded program using a C host as Wren has no built in support for named pipes.
As in the case of the C example, we run the 'write' loop on a separate thread and using a separate VM. The 'tally' variable is stored on the C side so it can be shared by both VM's.
This works fine on Ubuntu 20.04 and should work on other Linux distros though I can't vouch for anything else.
<syntaxhighlight lang="wren">/* IPC_via_named_pipe.wren */
var InputFifo = "in"
var OutputFifo = "out"
var O_RDONLY = 0
var O_WRONLY = 1
var PIPE_BUF = 4096
class Fifo {
foreign static make(path, oflag)
}
class File {
foreign static open(path, flags)
foreign static write(fd, str, size)
foreign static read(fd, size)
foreign static close(fd)
}
class C {
foreign static usleep(usec)
foreign static tally
foreign static tally=(newTally)
}
class Loops {
static read() {
while (true) {
var fd = File.open(InputFifo, O_RDONLY)
var len
while ((len = File.read(fd, PIPE_BUF)) > 0) C.tally = C.tally + len
File.close(fd)
}
}
static write() {
while (true) {
var fd = File.open(OutputFifo, O_WRONLY)
var ts = C.tally.toString + "\n"
File.write(fd, ts, ts.bytes.count)
File.close(fd)
C.usleep(10000)
}
}
}
Fifo.make(InputFifo, 438)
Fifo.make(OutputFifo, 438)</syntaxhighlight>
<br>
We now embed this script in the following C program, build and run from one terminal.
<syntaxhighlight lang="c">/* gcc IPC_via_named_pipe.c -o IPC_via_named_pipe -lpthread -lwren -lm */
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <pthread.h>
#include "wren.h"
/* C <=> Wren interface functions */
size_t tally = 0;
void C_make(WrenVM* vm) {
const char *pathname = wrenGetSlotString(vm, 1);
mode_t mode = (mode_t)wrenGetSlotDouble(vm, 2);
int res = mkfifo(pathname, mode);
wrenSetSlotDouble(vm, 0, (double)res);
}
void C_open(WrenVM* vm) {
const char *pathname = wrenGetSlotString(vm, 1);
int flags = (int)wrenGetSlotDouble(vm, 2);
int fd = open(pathname, flags);
if (fd < 0) {
perror(NULL);
}
wrenSetSlotDouble(vm, 0, (double)fd);
}
void C_write(WrenVM* vm) {
int fd = (int)wrenGetSlotDouble(vm, 1);
const char *str = wrenGetSlotString(vm, 2);
size_t count = (size_t)wrenGetSlotDouble(vm, 3);
ssize_t res = write(fd, (const void *)str, count + 1);
wrenSetSlotDouble(vm, 0, (double)res);
}
void C_read(WrenVM* vm) {
int fd = (int)wrenGetSlotDouble(vm, 1);
size_t nbyte = (size_t)wrenGetSlotDouble(vm, 2);
char buf[nbyte];
ssize_t res = read(fd, buf, nbyte);
wrenSetSlotDouble(vm, 0, (double)res);
}
void C_close(WrenVM* vm) {
int fd = (int)wrenGetSlotDouble(vm, 1);
int res = close(fd);
wrenSetSlotDouble(vm, 0, (double)res);
}
void C_usleep(WrenVM* vm) {
useconds_t usec = (useconds_t)wrenGetSlotDouble(vm, 1);
int res = usleep(usec);
wrenSetSlotDouble(vm, 0, (double)res);
}
void C_getTally(WrenVM* vm) {
wrenSetSlotDouble(vm, 0, (double)tally);
}
void C_setTally(WrenVM* vm) {
size_t newTally = (size_t)wrenGetSlotDouble(vm, 1);
tally = newTally;
}
WrenForeignMethodFn bindForeignMethod(
WrenVM* vm,
const char* module,
const char* className,
bool isStatic,
const char* signature) {
if (strcmp(module, "main") == 0) {
if (strcmp(className, "Fifo") == 0) {
if (isStatic && strcmp(signature, "make(_,_)") == 0) return C_make;
} else if (strcmp(className, "File") == 0) {
if (isStatic && strcmp(signature, "open(_,_)") == 0) return C_open;
if (isStatic && strcmp(signature, "write(_,_,_)") == 0) return C_write;
if (isStatic && strcmp(signature, "read(_,_)") == 0) return C_read;
if (isStatic && strcmp(signature, "close(_)") == 0) return C_close;
} else if (strcmp(className, "C") == 0) {
if (isStatic && strcmp(signature, "usleep(_)") == 0) return C_usleep;
if (isStatic && strcmp(signature, "tally") == 0) return C_getTally;
if (isStatic && strcmp(signature, "tally=(_)") == 0) return C_setTally;
}
}
return NULL;
}
static void writeFn(WrenVM* vm, const char* text) {
printf("%s", text);
}
void errorFn(WrenVM* vm, WrenErrorType errorType, const char* module, const int line, const char* msg) {
switch (errorType) {
case WREN_ERROR_COMPILE:
printf("[%s line %d] [Error] %s\n", module, line, msg);
break;
case WREN_ERROR_STACK_TRACE:
printf("[%s line %d] in %s\n", module, line, msg);
break;
case WREN_ERROR_RUNTIME:
printf("[Runtime Error] %s\n", msg);
break;
}
}
char *readFile(const char *fileName) {
FILE *f = fopen(fileName, "r");
fseek(f, 0, SEEK_END);
long fsize = ftell(f);
rewind(f);
char *script = malloc(fsize + 1);
fread(script, 1, fsize, f);
fclose(f);
script[fsize] = 0;
return script;
}
WrenVM *vm, *vm2;
void read_loop() {
wrenEnsureSlots(vm, 1);
wrenGetVariable(vm, "main", "Loops", 0);
WrenHandle *method = wrenMakeCallHandle(vm, "read()");
wrenCall(vm, method);
wrenReleaseHandle(vm, method);
}
void* write_loop(void *a) {
wrenEnsureSlots(vm2, 1);
wrenGetVariable(vm2, "main", "Loops", 0);
WrenHandle *method = wrenMakeCallHandle(vm2, "write()");
wrenCall(vm2, method);
wrenReleaseHandle(vm2, method);
}
int main(int argc, char **argv) {
WrenConfiguration config;
wrenInitConfiguration(&config);
config.writeFn = &writeFn;
config.errorFn = &errorFn;
config.bindForeignMethodFn = &bindForeignMethod;
vm = wrenNewVM(&config);
vm2 = wrenNewVM(&config);
const char* module = "main";
const char* fileName = "IPC_via_named_pipe.wren";
char *script = readFile(fileName);
WrenInterpretResult result = wrenInterpret(vm, module, script);
switch (result) {
case WREN_RESULT_COMPILE_ERROR:
printf("Compile Error!\n");
break;
case WREN_RESULT_RUNTIME_ERROR:
printf("Runtime Error!\n");
break;
case WREN_RESULT_SUCCESS:
break;
}
wrenInterpret(vm2, module, script);
pthread_t pid;
pthread_create(&pid, 0, write_loop, 0);
read_loop();
wrenFreeVM(vm);
wrenFreeVM(vm2);
free(script);
return 0;
}</syntaxhighlight>
<br>
{{out}}
Finally we can test that this is working correctly by typing in the following commands from a different terminal. The string lengths returned will, of course, include the final zero byte.
<pre>
$ cat out
0
$ echo test > in
$ cat out
5
$ echo "named pipe" > in
$ cat out
16
</pre>
=={{header|zkl}}==
zkl doesn't open pipes but it knows about them (on Unix anyway as they are just a file). So, outside of the program, create two named pipes and read/write to them inside the program.
{{trans|C}}
<syntaxhighlight lang="zkl">pipe:=Thread.Pipe(); // NOT a Unix pipe, for inter-thread commication
fcn writeLoop(pipe){ // a thread
out:=File("out","w");
foreach tally in (pipe){ out.writeln(tally); out.flush(); }
println("writeLoop done");
}.launch(pipe);
fcn readLoop(pipe){ // a thread
tally:=0;
in:=File("in","r").howza(3); // open for read, reading characters
while(1){ // named pipe sets EoF after writer exits
foreach c in (in){ pipe.write(tally+=1) } // read bytes until EoF
}
in.close();
println("readLoop done");
}.launch(pipe);
while(1){ Atomic.sleep(10000); } // veg out while other talk</syntaxhighlight>
{{out}}
Terminal 1:
<pre>
$ mkfifo in; mkfifo out
<wait until other two terminals get going>
$ echo "hello world" > in
$ cat ../Tests/lorem_ipsum.txt >in
</pre>
{{out}}
In Terminal 2, start the program:
<pre>$ zkl bbb</pre>
{{out}}
Terminal 3:
There is pretty much no delay - character enters "in", "out" sees tally.
<pre>
$ cat out
1
2
3
4
5
6
7
8
9
10
11
12
...
1391
1392
1393
1394
1395
1396
1397
1398
1399
</pre>
{{omit from|GUISS}}
{{omit from|Mathematica}}
{{omit from|ZX Spectrum Basic}}
| |||