I'm trying to use named pipes in a project. I have two terminals open, Terminal A and Terminal B.
In terminal A, I issued this command:
mkfifo myFifo && tail -f myFifo | csh -s
It seems as if standard out is being redirected somewhere else, though, because my prompt disappears and some commands aren't reflected in terminal A.
For example, if in terminal B I begin a python session via issuing echo "python" > myFifo, then echo "print 'Hello, World'" > myFifo, I don't see Hello, World in terminal A.
However, if I issue echo ls > myFifo within terminal B, I see the correct output from ls in terminal A.
Does anyone know why sometimes the output appears and sometime it doesn't?
I'm running on CentOS 6.6
Thanks,
erip
You read from the FIFO with csh, if you start an interactive Python shell in csh, then it won't be reading from the FIFO because it's busy running python.
Python doesn't somehow automagically do a REPL on the FIFO. How should it even know about the FIFO? It has no knowledge of it.
You could, perhaps, tell Python to read commands from the FIFO with something like:
>>> import os, sys, time
>>> fifo = open(os.open('myFifo', os.O_NONBLOCK), 'r')
And then:
$ echo 'print(42+5)' > ! myFifo
Will give you:
>>> eval(fifo.read())
47
Perhaps there's also a way to tell Python to read commands from myFifo by overwriting sys.stdin, but I can't get that working in my testing.
It's a bit unclear to me what exactly you're trying to achieve here, though. I suspect there might be another solution which is much more appropriate to the problem you're having.
Related
I'm running a script in solaris 11 with different results depending of the shell used.
The script has an echo redirecting to a file given by an environment value:
echo "STARTING EXEC" >> $FILE
ps. EXEC is just the message the script show, it's not using exec command.
If I execute the script without the variable FILE defined (using /usr/bin/ksh):
./start.sh[10]: : cannot open
and the script continue the execution.
The flags for ksh are:
echo $-
imsuBGEl
But if I change to /usr/xpg4/bin/sh, the script show me the echo in stdout and there is no error shown.
The flags for xpg4 sh are:
echo $-
imsu
I tried to change the flags with set +- (I can't remove El flags, but BG are removed ok), but can't get the same behavior.
Is there anything I can do to get the same result using ksh without cannot open error?
/usr/bin/ksh --version
version sh (AT&T Research) 93u 2011-02-08
I'll want the script keep going, showing the message in stdout, instead of showing the error just like it does now.
Like shellter said in the comments, the good thing to do is to check if the FILE variable is defined before doing anything. This is a script migration from an HPUX to a SOLARIS environment, and client think they must have the same result as before (we unset FILE variable before execution to test it).
You are likely running Solaris 11, not Solaris 64.
Should you want to have your scripts to work under Solaris 11 without having to search everywhere the bogus redirections, you can simply replace all shebangs (first line) by #!/usr/xpg4/bin/sh.
The final solution we are going to take is to install the ksh88 package and use it like default shell (/usr/sunos/bin/ksh). This shell have the same behavior the client had before, and we can let the scripts with no modifications.
The ksh used in solaris 11 is the 93 (http://docs.oracle.com/cd/E23824_01/html/E24456/userenv-1.html#shell-1)
Thanks #jlliagre and #shellter for your help.
In case of "ls" command it runs with and without the prefix "!". In case of "cat fileName" it's the same, but when you consider "wc -l fileName" it works only with "!" prefix.
When you combine cat and wc command "cat fileName | wc -l" executed successfully without "!" prefix.
I don't understand the logic behind this prefix "!" in ipython.
Thank you in advance
(I am new to python programming, if it sounds silly question please forgive me.)
IPython tries to make interactive programming as comfortable as possible. Some shell builtins like ls, cd or cat are basic commands to navigate in unix shells. IPython, as a "Python Shell" provides the same functionally for convenience. Along with features like colored output, etc.
The !command is for executing arbitrary shell code and is much more powerful. It can be used to run any command you can type in a normal shell and can also catch its output.
Compare ls with !ls. The former will print the content in your current directory with nice coloring. The latter will print the same list, but just plain text.
But note that you can do really cool things with !command:
files = !ls
for f in files:
print("I like this file:", f)
Which reads the output of ls into a python array files which you can use in your code just like any other array.
To sum up: if you just want to navigate, you usually use the standard commands, if available. If you need to capture the output or run programs you have to use the !command syntax.
I have some code in python that works but is unfortunately super slow. Someone at #python suggested that I can run the code through a profiler to see the lines and functions in which the code was taking the most amount of time.
The python source code that I want to profile reads from STDIN. But since the input is large I compiled the input as a file so that I can simply redirect it to the python code at the shell. So at the shell, I issue the command..
cat input | python pythonsource.py
The problem is, when I try to run the profiler in ipython I can't seem to find a way to redirect the input to the python code. At the ipython shell, I tried,
run -p -l 1.0 pythonsource.py input (didn't work. simply waits at STDIN for input)
run -p -l 1.0 pythonsource.py << input (didn't work)
run -p -l 1.0 cat input | python pythonsource.py (didn't work.)
I'm not sure how to do I can make the ipython profiler command redirect the input to STDIN for the pythonsource to read from. Could someone please tell me how to fix this? Or have I got it totally wrong? Maybe there is some other cleaner, more smarter way of profiling python code?
And maybe what I ask next should be a part of another question..but I was wondering what does ipython mean when it refers to "primitive calls" in some of the output of the ipython profiler?
Thank you.
The right way to redirect input on the shell commandline is as follows:
cat input | run -p -l 1.0 python pythonsource.py
run -p -l 1.0 python pythonsource.py < input
The syntax << string creates a "here document", it does not redirect input.
From the python prompt (and hopefully in ipython), you can redirect standard input like this:
import sys
save_stdin = sys.stdin
sys.stdin = open('input')
run -p <etc.>
sys.stdin = save_stdin # Restore the real stdin
Or (recommended) you could rewrite your source to work with a filename: If you call it as follows, "input" will be in sys.argv[1] and you can open it and read from it:
python pythonsource.py input
In Unix, I have a process that I want to run using nohup. However this process will at some point wait at a prompt where I have to enter yes or no for it to continue. So far, in Unix I have been doing the following
nohup myprocess <<EOF
y
EOF
So I start the process 'myprocess' using nohup and pipe in a file with 'y' then close the file. The lines above are effectively three seperate commands - i.e. I hit enter on the first line in UNIX, then I get a prompt where I enter 'y' and then press enter to then finally type 'EOF' and hit return again.
I want to know execute this in Perl but I am not sure how I can execute this command as it is over three lines. I don't know if the following will work....
my $startprocess = `nohup myprocess <<EOF &
y
EOF
`
Please help - thank you!
I think your proposal will work as is. If not, try replacing the redirect with a pipe:
my $startprocess = `(echo "y" | nohup myprocess) &`;
Also, depending on WHY you are doing a nohup, please look at the following pure Perl daemonizing approach using Proc::Daemon : How can I run a Perl script as a system daemon in linux?
Expect for interactive programs can be used as well.
I have script lets say:
C:\foo.bsh
I want to be able to run this command via the windows run command:
Start -> Run
Windows Key + R
and type something small like 'foo' and hitting return.
However, I do not want a cmd prompt to be visible. This script does some preprocessing for an IDE. I do not want the cmd prompt to be open for the lifetime of the IDE process.
I have tried:
1) Creating a bat file with the following contents:
c:\cygwin\bin\bash --login "C:\foo.bsh" (this fails because it keeps a cmd open)
2) Converting the above bat file to an exe using bat_2_exe_converter (does not make the cmd silent)
thoughts?
EDIT: The solution so far suggests something to type from an actual cygwin shell. I am trying to get a faster solution by having something short I can type in the Windows run command. Also, the nohup command; exit doesn't automatically kill the box - however I can manually kill it without killing the IDE process. The run command accepts shortcuts (.lnk's), bat's, exe's.
Try the run.exe command of cygwin. It is a big install, a complete unix environment for your Windows machine. Suppose you installed it at c:\cygwin\.
No mystery, just run c:\cygwin\bin\run.exe <your command here> and you will have your no dos window execution.
You can run it from any DOS window (run cmd.exe from the start menu). You don't need to run it from cygwin.
To make it easier, append C:\cygwin\bin to your %PATH% env var (My Computer → Properties → Advanced → Environment Variables) (Kudos to Felipe Alvarez comment).
Now you can just type
c:\cygwin\bin\run.exe "C:\foo.bsh"
You must create a link in your Start Menu with this command so will be able to run it with Win-R.
Here is the man page of the runcommand:
$ man run
RUN(1) run 1.3.0 RUN(1)
NAME
run - start programs with hidden console window
SYNOPSIS
run [ -p path ] command [ -wait ] arguments
runcommand [ -p path ] [ -wait ] arguments
DESCRIPTION
Windows programs are either GUI programs or console programs. When
started console programs will either attach to an existing console
or create a new one. GUI programs can never attach to an exiting con‐
sole. There is no way to attach to an existing console but hide it if
started as GUI program.
run will do this for you. It works as intermediate and starts a pro‐
gram but makes the console window hidden.
With -p path you can add path to the PATH environment variable.
Issuing -wait as first program argument will make run wait for program
completition, otherwise it returns immediately.
The second variant is for creating wrappers. If the executable is
named runcommand (eg runemacs), run will try to start the program (eg
emacs).
EXAMPLES
run -p /usr/X11R6/bin xterm
run emacs -wait
runemacs -wait
run make -wait
AUTHORS
Charles S. Wilson
Harold L Hunt II
Jehan Bing
Alexander Gottwald
Version 1.3.0 November 2005 RUN(1)
You can use either...
c:\cygwin\bin\bash -l /path/to/script_to_interpret.sh
...or...
c:\cygwin\bin\bash -l -c /path/to/executable_script.sh
Note: the -l flag tell bash to "act as if it had been directly invoked by login" and use Bash Startup Files. This is important in that it sets your $PATH and other things you rely on when you launch a cygwin terminal. If you don't include -l or --login you will get "command not found" when you try to call anything except of a bash builtin.
The difference between the 2 is like the difference between doing...
bash script_to_interpret.sh
...and...
./executable_script.sh
...in *nix. The former interprets the script using bash. The latter executes the script (only if it has chmod +x executable_script.sh) and interprets it according to its "shebang" line. The latter method is also what you want to do if your executable is not a script at all, like a *nix binary compiled from source.)
It has been bugging me for a while I couldn't find the solution for this, but I finally got the right mix together.
You can simply do the following if you have cygwin on your PATH:
run bash test.js
If cygwin is not on your path, you can do this:
c:\cygwin\bin\run.exe -p /bin bash test.js
If you are looking for more control over the created window (maximize, etc) it looks like you can use cygstart also.
Sources:
- neves answer above (though that wasn't enough by itself for me personally to figure it out)
- http://cygwin.com/ml/cygwin/2008-09/msg00156.html
As the terminal can't close while your script is still running, try the command:
"nohup C:\foo.bsh; exit"
This way your script will be backgrounded and detached from the terminal, and it should exit quickly so the terminal goes away. I think that the window may still 'flash' with this approach, but the results should be better than what you're getting.
I'm running Cygwin64 and the xwin server link points to:
C:\cygwin64\bin\run.exe /usr/bin/bash.exe -l -c /usr/bin/startxwin.exe
This creates an icon AND a notification on the taskbar. I don't like that. The icon is rather useless, the notification has all your menu options from .XWinrc.
So... I wrote a .vbs script to silently run this command and make the icon go away:
Set objShell = CreateObject("WScript.Shell")
objShell.Run("C:\cygwin64\bin\run.exe /usr/bin/bash.exe -l -c /usr/bin/startxwin.exe"), 0
Another imperfect possibility is to run the script via a shortcut and set the shortcut's Run option to "minimized".
Go to the directory where you have installed cygwin(on my machine it is c:/cygwin64/bin)
Once there simply type "bash.exe"