Wednesday, May 12, 2010

Abbreviating output to a line in the terminal

A very long time ago, I quickly whipped together a Perl script that will reduce the standard output from another program to just a line, prefixed with an animation character, and optionally suffixed with ellipses if the line is too long. It is useful if only the most recent output is significant, and that I only want to know if the program is making progress. It can be applied to many commands, e.g.
  • tar zxvf source-1.1.0.tar.gz | abbrev
  • unzip | abbrev
  • make | abbrev
  • tail -F /var/log/messages | abbrev
I've long wanted to rewrite that Perl script in C, and now here it is (abbrev.c). The program is licensed under GNU General Public License, version 3.

Compiling is simple if you're using GNU make:
make abbrev
You don't need to supply a Makefile. The implicit rule will work. You can optionally supply CFLAGS=-O3 to the make command, as well as optionally strip the executable after make. To install, just move the executable to somewhere in your PATH. It should compile out of the box on Linux and Mac OS X.

There are some subtle features that one might not notice:
  • Output is throttled to a certain frame rate (default 30 fps).
  • Resizing the terminal window will cause the line length to adjust accordingly.
Hope you enjoy it.

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