Bash – Timing of ps piped to grep

When you type command that don't exists in your system bash runs function command_not_found_handle(). In this function there is a call to /usr/lib/command-not-found script that prints messages.

Ubuntu 12.04

My first guess to change source of this script to print messages to stdout instead stderr, but when I was reading source of script I found that you can configure it to just ask you if you want to install missing package.

If you export variable COMMAND_NOT_FOUND_INSTALL_PROMPT you will be asked to install missing package:

pbm@ubuntu:~$ git
The program 'git' is currently not installed.  You can install it by typing:
sudo apt-get install git
pbm@ubuntu:~$ export COMMAND_NOT_FOUND_INSTALL_PROMPT=""
pbm@ubuntu:~$ git
The program 'git' is currently not installed.  You can install it by typing:
sudo apt-get install git
Do you want to install it? (N/y)y
sudo apt-get install git
[sudo] password for pbm: 

Older versions of Ubuntu

Unfortunately there is no COMMAND_NOT_FOUND_INSTALL_PROMPT so I can find few other options:

1) Install package from 12.04 - it shouldn't be the problem - it's only few scripts in Python so it should work (untested!).

2) Change stderr to stdout. To do it edit file /usr/lib/python2.7/dist-packages/CommandNotFound/CommandNotFound.py and change stderr to stdout in lines 237 and 240.

After that you can use it in this way:

pbm@ubuntu:~$ git
The program 'git' is currently not installed.  You can install it by typing:
sudo apt-get install git
pbm@ubuntu:~$ `git`
//Installation begins

If you add -y option to apt-get command in lines 237 and 240 you could also use syntax !! | sh.

3) You can also modify this script from line 242 in this way:

print >> sys.stderr, _("You can install it by typing:")
f = open("%s/.install-missing" % os.path.expanduser('~'),'w')
print >> sys.stderr, "sudo apt-get install %s" % packages[0][0]
print >> f, "sudo apt-get install %s" % packages[0][0]
f.close()

In this way you will get your command in file ~/.install-missing, so you may create alias:

alias im="chmod +x ~/.install-missing; ~/.install-missing"

If you call im package will be installed.

cat out | netcat foo.bar.org 4000 > in &

I think the problem is that cat will exit as soon as it receives an EOF from the out pipe. And when cat exits, the rest of the pipeline (including netcat) gets terminated as well.

Try something like this instead:

while true; do cat out; done | netcat foo.bar.org 4000 > in &

Thus, cat gets restarted as often as needed, and any EOFs appearing in the out pipe are effectively handled.