Use Perl with UNIX tools
Perl is very useful programming language for not only programmers but also system administrators.
Perl has good compatibility with UNIX philosophy - `Make each program do one thing well'. Experienced system administrators use simple tools by combination. But sometimes these long one-liner looks like too complex.
For example, see this command line. Note that `^[' is ESC character.
# tail -f /var/log/messages | sed -e 's/\(error\)/^[[7m\1^[[m^G/'
It works like this: to invert highlighting matching string `error' and send bell.
But I think there are some problems to write literal escape character.
- It's hard to read. I can't remember `ESC[7m' means invertion. This looks like magic (of voodoo).
- It's hard to write. You must write raw ESC character, so you cannot copy and paste this command line.
I fixed these problem to write simple filter program by Perl. This is escfilter, simple grep-like tool.
# tail -f /var/log/messages | escfilter --reverse error
I think this approach is bit better than previous way.
- Easy to read. There is no longer escape sequence in command line.
- Easy to write. --help option will inform you how to use it.
escfilter on gist
Yuuki Namikawa (@namikawa) was described how to processing log file with escape sequence by sed.
Kato Kazuyoshi (kzys) was improved escfilter script by using Term::ANSIColor.