spawn

I'm learning to write a TCL (expect) scripts and I notice that some examples show to use spawn, while others show the command exec. I tried googling, but can't find what is the difference? Suppose I call 'exec' in a middle of a long expect script, what can I expect to happen? spawn is an expect command not a tcl command. exec is a tcl command. spawn creates a process. The processes' input and output are connected to expect for use by the other expect commands: send , expect and interact . exec creates a subprocess under tcl. In general the tcl is suspended until the subprocess completes.

I would like to execute the following command using nodejs Spawn on a Debian system : /usr/bin/apt-get upgrade -s | tail -1 | cut -f1 -d' ' I want to use spawn and not exec because of future use of root only commands and i don't want to allow a full shell access (i will update the visudo file with correct commands) Here is my code const apt = spawn('/usr/bin/apt-get', ['upgrade', '-s']); const tail = spawn('tail', ['-1']); const cut = spawn('cut', ['-f1', '-d" "']); apt.stdout.on('data', (data) => { tail.stdin.write(data); }); tail.stdout.on('data', (data) => { cut.stdin.write(data); }); cut

I have the following test php to do a fork/spawn process, where the test also attempts to kill the child process (zombie) after is completes.. I'd like to have a more efficient process, where any child processes are immediately removed from the process table as soon as possible. The current attempt fills up the process table, and causes a memory allocation issue that shuts down the system. The app is running on a Fedora/Centos system. I'm running into a memory allocation err when this runs, and there are too many processes that get spawned, before they get removed. Any pointers would be

My question is, after spawning a process, the child process is looping to get data from its stdin. I would like to write new data to it using either Echo.Process.pipes[0].write(data) or Echo.Process.writeToChild(0,data), but both do not work. Would someone explain what's going on? Or how do I go around this problem? This is the error I got: --- <exception caught here> --- File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-9.0.0-py2.6-linux-x86_64.egg/twisted/internet/selectreactor.py", line 146, in _doReadOrWrite why = getattr(selectable, method)() File "/usr/local/encap