stdin

I have a loop that does some work and prints a lot of info to stdout. Over and over again (it's a loop...) What I'd like to do is to detect when / if user presses a key (it can be an arrow, enter, or a letter), and do some work when that happens. This should have been a very simple subsubtask, but I've spent last four hours trying different approaches and getting pretty much nowhere. This needs only work in Linux. Best I could get is something like this below. But that works partially, catching the keys only if within the 0.05 sec. import sys,tty,termios class _Getch: def __call__(self, n=1):

I wan to create a pipe between 3 commands: cat = subprocess.Popen("cat /etc/passwd", stdout=subprocess.PIPE) grep = subprocess.Popen("grep '<usernamr>'", stdin=cat.stdout, stdout=subprocess.PIPE) cut = subprocess.Popen("cut -f 3 -d ':'", stdin=grep.stdout, stdout=subprocess.PIPE) for line in cut.stdout: # process each line here But python documentation says: Use communicate() rather than .stdin.write , .stdout.read or .stderr.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process. then how should I use cut.stdout ? Can someone explain

I thought this program will echo my console input line by line: import os, sys for line in sys.stdin: print line Unfortunately it waits for EOF ( Ctrl + D ) and then it produces output. How should I modify my program to get output line by line? Python 2.x: for line in iter(sys.stdin.readline, ''): print line, Python 3.x: for line in iter(sys.stdin.readline, ''): print(line, end='') See the documentation on iter() with two arguments, it actually has reading from a file like this as one of the examples. Python 2.x: while True: sys.stdout.write(sys.stdin.readline()) Python 3.x: while True: print

The sys.stdin.readline() waits for an EOF (or new line) before returning, so if I have a console input, readline() waits for user input. Instead I want to print help and exit with an error if there is nothing to process, not wait for user input. Reason: I'm looking to write a python program with command line behaviour similar to grep . Test cases: No input and nothing piped, print help $ argparse.py argparse.py - prints arguments echo $? # UNIX echo %ERRORLEVEL% # WINDOWS 2 Command line args parsed $ argparse.py a b c 0 a 1 b 2 c Accept piped commands $ ls | argparse.py 0 argparse.py 1 aFile

How can I check if a CLI program, that I just started with CreateProcess(), is waiting for input from stdin with the Windows C API? as some of the comments above have said, you cannot check if your program is waiting for stdin once it has already started waiting. You could use an event handler or you could simply have a read from stdin with a timeout, where on occurrence of the timeout you flag that you are waiting for input and start waiting with a timeout again. 来源： https://stackoverflow.com/questions/10803122/how-can-i-check-if-a-cli-program-is-waiting-for-input-from-stdin

I need to run some python scripts from node. Since my python scripts use complex structures I figured would be better if I only loaded those structures once and then run some the specific scripts (tasks) using the structures. On node I want to run a script forever (or until I say it can terminate) and keep sending on-demand messages to this script. This script would create a process, using python multiprocessing , to run the specific task and start listening again. A use case would be: Node starts, and wakes python script Some action on the node client causes it to send a command to the python

I am trying to understand the behavior of the three streams - stdout , stdin and stderr . I couldn't get the answer from any textbook, so I came here. I know that these three are stored in file descriptor table with file descriptors 0 (stdin), 1 (stdout) and 2 (stderr). I am also aware that these are not merely file descriptors but I/O streams which can be redirected. Ok, so how about sharing? Consider the three cases: When a fork() is called : The child process and parent process shares file descriptors, but do they have the same stdin, stdout and stderr ? When a thread is created : Threads