Temperance bearing an hourglass; detail of Lorenzetti's Allegory of Good Government, 1338

Frequently I need to execute a fairly long running task, such as unpacking a large tar file or running a long build.  I want to get feedback on the progress of the task, but I don’t necessarily want to fill my terminal window with lots of superfluous text by using the verbose output option.  Not only is the scrolling text distracting and difficult to follow, outputting the text can be  a significant bottleneck on slow connections.

To solve this problem I use a script called “dots,” which I list below.  This script prints a single period character for every 1000 lines of input.  You can specify a different number of lines necessary to create a dot as the first argument to the command.  Any command with verbose output can be piped into dots to generate a simple progress bar.

#!/usr/bin/perl

$| = 1;  # flush output immediately
$i = 0;

if ($#ARGV < 0) {
  $number = 1000;
} else {
  $number = shift(@ARGV);
}

while (<STDIN>) {
  print '.' unless ($i % $number);
  $i++;
}

print "\n";

jdblair@zaphod:~/src$ tar xvfj linux-2.6.30.5.tar.bz2 | dots
..............................

jdblair@zaphod:~/src$ rm -rfv linux-2.6.30.5 | dots
..............................

If you still want to be able to check the output, such as the text generated by a long running make command, use the tee command to generate a log file.  This example generates a dot for every 10 lines of output, since the compiler output is generated comparatively slowly.

jdblair@zaphod:~/src/linux-2.6.30.5$ make bzImage 2>&1 | tee build.log | dots 10
................................................................................
................................................................................
....................

$ rm *;*

The response from the shell was this:

sh: *: command not found

Then, to my horror, when I listed the directory I could see all my files were gone.

The unix nerds in the audience will have already noticed what happened.  You see, the semicolon is the magic character that ends a command line.  I had told the shell to remove all my files then run a command called *.

Game over, at least for all the files in my home directory.

This story came up in a particularly geeky thread yesterday on Facebook, and Nick Shapiro told me a trick he learned from our mutual friend Greg Sutter.

Put a file called “-i” in directories containing vital files.  If you run “rm *” the file called “-i” tricks rm into running in “interactive” mode, which gives you a chance to bail out.

Here’s an example:

$ mkdir tmp; cd tmp
$ touch ./-i
$ touch foo bar baz
$ rm *
rm: remove regular empty file `bar'?

Now you have a chance to notice what happened and hit control-c to exit.

To remove the file, use

$ rm ./-i

Another handy related trick: a perl one-liner is also a great way to remove files with tricky names:

$ perl -e "unlink('-i');"

This trick also works great for files with other inconvenient names, like -, –, ;, >, and <, for which the “./” technique above doesn’t work.

UPDATE:

My friend Joe Ardent points out something I had forgotten: The GNU convention is to ignore any arguments after “–” in the argument list.  Thus, you can also do this:

$ touch -- -i
$ rm -- -i

Joe also reminds me that you can escape special shell characters using the backslash character. Thus, “rm \<” works, which is simpler than the perl one liner.  Just when you think you’re an expert in something…

Here’s what you do:

1. If necessary, make a small form in the shape you want the patch to take.
2. Fill the form, or hole you are filling, with baking soda.
3. Dribble super glue into the baking soda until the powder is saturated. It will foam up a little. Do not be alarmed.  This is a feature.
4. Remove the form. This may require some sanding since it will now be attached by super glue.
5. Sand rough edges to taste.

I learned this trick from my friend Gary Brawer, who refers to the material as “amalgamated compound.” He explained that the name gives the otherwise banal sounding material more cred.

I watched Gary use “amalgamated compound” to repair a broken nut on a guitar (this is the plastic part at the top of the fret board that holds the strings in their proper position) and was totally amazed by the speed and the quality of the result.

Gary runs Gary Brawer Guitar and Bass Repair. I can’t recommend him strongly enough if you have a guitar in need of some TLC.

It is mildly irritating that ctrl-w means “paste” in emacs, but it means “close window” in virtually any other application, or in Firefox, “close tab.” If I’m editing text in firefox (say, a wiki page or a blog post) I have tendency to type “ctrl-w” to paste text.

Bam, the tab closes, along with all my edits.

Luckily my friend Bill Richardson taught me to type “shift-ctrl-t.” In Firefox this puts the tab you just had open back, along with all the text in the fields just as you had left them.

Thank you Bill!

If you didn’t have any other tabs open, or you’re using another app (like, say, evolution) you’re out of luck.