Hello Mikael! Thank you, that makes it clearer. Different levels of abstraction and pipes of the OS level are represented as ports in Guile. I think I understand now. I quite like the ports concept with its many uses.
Best regards, Zelphir On 8/11/21 5:16 AM, Mikael Djurfeldt wrote: > Hi Zelphir! > > A port is a scheme level concept which represents input and output devices. > > Stdin, stdout and stderr are file descriptors which is an OS level concept. > > A pipe is also an OS level concept. It is a communication stream between two > processes. In the OS, it is represented as a file descriptor once opened. > > The function open-input-pipe creates a child process and opens a pipe from it. > In the OS, the pipe is represented as a file descriptor. This is represented > as a port at the scheme level. > > In Guile, this port also has some extra information: It has a type, #{read > pipe}, and also carries (i believe) some extra information, such as the > process identifier of the child process. > > Best regards, > Mikael > > Den ons 11 aug. 2021 03:14Zelphir Kaltstahl <zelphirkaltst...@posteo.de > <mailto:zelphirkaltst...@posteo.de>> skrev: > > Hello Guile users, > > I recently came across > https://www.draketo.de/software/guile-capture-stdout-stderr.html > <https://www.draketo.de/software/guile-capture-stdout-stderr.html> > <https://www.draketo.de/software/guile-capture-stdout-stderr.html > <https://www.draketo.de/software/guile-capture-stdout-stderr.html>> and > wrote a > commented version at > > https://notabug.org/ZelphirKaltstahl/guile-examples/src/master/input-output/stdout-stderr.scm > > <https://notabug.org/ZelphirKaltstahl/guile-examples/src/master/input-output/stdout-stderr.scm> > > <https://notabug.org/ZelphirKaltstahl/guile-examples/src/master/input-output/stdout-stderr.scm > > <https://notabug.org/ZelphirKaltstahl/guile-examples/src/master/input-output/stdout-stderr.scm>>. > > While looking at the code, I was starting to wonder, what the difference > between > a pipe and a port is. The reference manual does not say much about any > definition of what a pipe is at > https://www.gnu.org/software/guile/manual/html_node/Pipes.html > <https://www.gnu.org/software/guile/manual/html_node/Pipes.html> > <https://www.gnu.org/software/guile/manual/html_node/Pipes.html > <https://www.gnu.org/software/guile/manual/html_node/Pipes.html>> and pipe > procedure return values are also named port. > > However, in the REPL, they look not the same: > > ~~~~ > scheme@(guile-user)> (import (ice-9 popen)) > scheme@(guile-user)> (open-input-pipe "ls -al") > $2 = #<input: #{read pipe}# 13> > ~~~~ > > And here for ports: > > ~~~~ > scheme@(guile-user)> (call-with-output-string > (λ (port) > (display port))) > #<output: file 7fa2a99471c0>$6 = "" > ~~~~ > > Is a pipe just a special kind of port? Does it wrap a port? Or is it > perhaps > merely a different terminology used in different contexts in the reference > manual? > > Best regards, > Zelphir > > -- > repositories: https://notabug.org/ZelphirKaltstahl > <https://notabug.org/ZelphirKaltstahl> > > -- repositories: https://notabug.org/ZelphirKaltstahl