Ad Hoc Data Analysis From The Unix Command Line/Appendices

Appendix A: pcalc source code A perl read-eval-print loop. This makes a very handy calculator on the command line. Example usage: $ pcalc 1+2 3 $ pcalc "2*2" 4 $ pcalc 2*3 6 Source: #!/opt/third-party/bin/perl use strict; if ($#ARGV >= 0) { eval_print(join(" ",@ARGV)) } else { use Term::ReadLine; my $term = new Term::ReadLine 'pcalc'; while ( defined ($_ = $term->readline("")) ) { s/[\r\n]//g; eval_print($_); $term->addhistory($_) if /\S/; } } sub eval_print { my ($str) = @_; my $result = eval $str; if (!defined($result)) { print "Error evaluating '$str'\n"; } else { print $result,"\n"; } } Appendix B: Random unfinished ideas Ideas too good to delete, but that aren't fleshed out. Micro shell scripts from the command line Example - which .so has the object I want? Using backticks Example - killing processes by name kill `ps auxww | grep httpd | grep -v grep | awk '{print $2}'` Example - tailing the most recent log file in one easy step tail -f `ls -rt *log | tail -1` James' xargs trick James uses echo with xargs and feeds one xargs' output into another xargs in clever ways to build up complex command lines. tee(1) perl + $/ == agrep Example - Finding duplicate keys in two files Quick Plotting With gnuplot