Perl One Liners

Useful perl one liners explained

Transcript

1. Perl One Liners perl -e ‘print “Hello World\n”’ Tuesday, November 1, 2011
2. One Theory perl -e ‘...’ - run a one liner with no input perl -ne ‘...’ - run a one liner on every input line perl -pe ‘...’ - same as -ne, AND print each line perl -i files -e ‘...’ - edit files in place Note the quotes. A single quote prevents the shell from grabbing our program Tuesday, November 1, 2011
3. Core One Liners Write once, Use everywhere Tuesday, November 1, 2011
4. perl -pe 1 Tuesday, November 1, 2011
5. Print contents of standard input Print readme.txt: perl -pe 1 readme.txt Create a file named outfile perl -pe 1 > outfile Discussion Tuesday, November 1, 2011
6. perl -ne ‘print if 15..17’ Tuesday, November 1, 2011
7. Discussion Conditional printing of file contents selected lines only: print if 15..17 matched text only: print if /foo/ combined: print if /begin/.../end/ Tuesday, November 1, 2011
8. Discussion use -l if line-end char is an issue perl -nle ‘print if $_ eq reverse’ /usr/share/dict/words Tuesday, November 1, 2011
9. perl -e ‘print reverse <>’ Tuesday, November 1, 2011
10. Discussion Reverse order of lines This words because reverse imposes list context on the <> operator Can also reverse each line using perl -nle ‘print scalar reverse $_’ Tuesday, November 1, 2011
11. Line Numbers Tuesday, November 1, 2011
12. perl -ne ‘print “$. $_”’ Tuesday, November 1, 2011
13. Discussion Print input lines numbered $. is a special perl variable holding current line number Can use to print only even/odd lines: perl -ne ‘print if $. % 2 == 0’ Can use to print only non-blank lines: perl -ne 'print ++$n . " $_" if /./;' Count number of lines in a file perl -ne 'END {print $.}' Tuesday, November 1, 2011
14. Special Blocks: BEGIN & END Tuesday, November 1, 2011
15. perl -lne '$s += $_; END{ print $s/$.}' Tuesday, November 1, 2011
16. Discussion END allows running code when input ends Can use perl variables Note the -l for line ending magic Tuesday, November 1, 2011
17. perl -e '@a=<>; print @a[@a-3..@a]' Tuesday, November 1, 2011
18. Discussion Print n lines from the end of input (like tail) Use a buffer to remember Note the context: @a = <>; Tuesday, November 1, 2011
19. In Place Editing Tuesday, November 1, 2011
20. perl -p -i.bak -e 's/\bfoo\b/bar/g' *.c Original file (unmodified) will be saved as a .bak For example, a.c is backed up as a.c.bak Tuesday, November 1, 2011
21. In Place Editing Use -i for in place editing Use regular expressions for search & replace Can also use: perl -i.old -ne 'print unless 1 .. 10' foo.txt perl -i’*.bak’ -pe 's/(\d+)/ 1 + $1 /ge' file1 file2 Tuesday, November 1, 2011
22. Modules One Liners Write Less, Do More Tuesday, November 1, 2011
23. perl -MFile::Compare -e 'compare("list","bar") and die "Not The Same"' Tuesday, November 1, 2011
24. perl -MFile::Copy -e 'copy("foo","buz")' Tuesday, November 1, 2011
25. Discussion Simple file operations modules Get a list of all core modules installed with your perl using perldoc perlmodlib Get a list of search paths for modules using perl -e ‘perl -e '$,="\n"; print @INC' Tuesday, November 1, 2011
26. CPAN Over 20,000 perl software packages Automatically install using cpan Easy to use Tuesday, November 1, 2011
27. Facebook LWP Finance::Currency::Co nvert::Yahoo Dancer CPAN One Liners Tuesday, November 1, 2011
28. perl -MData::Dumper -MFacebook::Graph -e 'print Dumper( Facebook::Graph->new->query-> find("ynonperek")->request->as_hashref)' Tuesday, November 1, 2011
29. Discussion Facebook::Graph can access all data stored on facebook in a perlish way Use Data::Dumper to print the result Install with cpanm Facebook::Graph Tuesday, November 1, 2011
30. perl -MLWP::Simple -e ‘getstore(“http://www.google.com”, “index.html”);’ URL To Save Store Location Tuesday, November 1, 2011
31. perl -M5.12.0 -MFinance::Currency::Convert::Yahoo -e "say Finance::Currency::Convert::Yahoo::convert (1, 'USD', 'GBP')" Tuesday, November 1, 2011
32. perl -MDancer -e ‘set public => “.”; dance Tuesday, November 1, 2011
33. Discussion Dancer is a mini framework for writing web applications The above starts a debug server, serving all files in current path on port 3000 Install with cpanm Dancer Tuesday, November 1, 2011
34. Q & A Tuesday, November 1, 2011
35. Thank You Ynon Perek ynonperek@hotmail.com ynonperek.com Tuesday, November 1, 2011