Perl In The Command Line
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- The document summarizes common Perl command line options for testing, debugging, importing modules, looping, editing files in-place, line endings and autosplitting. It provides examples of using many of the options. - Key options covered include -c for syntax checking, -w/-W/-X for warnings, -d for debugging, -e for eval, -M for module import, -n/-p for looping through files, -i for in-place editing, -l for line endings and -a/-F for autosplitting. - Many examples demonstrate how these options can be combined with Perl code to perform tasks like searching/replacing text in files from the command line.
![perl -MLWP::Simple -e 'print get($ARGV[0]), "\n"' http://perl.com Better as an alias.](https://image.slidesharecdn.com/perlintheshell-090914014845-phpapp01/85/Perl-In-The-Command-Line-15-320.jpg)
Perl In The Command Line
- 1. Perl in the Command Line
- 2. -c: Test Compiling -c : causes Perl to check the syntax of the program and then exit without executing it.
- 3. It will execute BEGIN , UNITCHECK , CHECK , and use blocks, because these are considered as occurring outside the execution of your program.
- 4. It will not execute INIT and END blocks.
- 5. -w, -W and -X: Warnings -w : This turns on warnings that Perl will then give you if it finds any of a number of problems in your code. The -w option has been replaced by the use warnings pragma.
- 6. -W: Enables all warnings regardless of no warnings or $^W .
- 7. -X: Disables all warnings regardless of use warnings or $^W .
- 9. -d: Debugging -d : This option puts you into the Perl debugger.
- 10. -d:DProf : executes the program using the Devel::DProf profiler, combined with dprofpp may help you to find where is your program slow.
- 11. $> perldoc perldebtut $> perldoc perldebug
- 12. -e: eval -e: allows you to define code to be executed by the compiler. $> perl -e 'print "Hello World"' "Hello World" program in the shell. -E : like -e, but enables all optional features
- 13. -M: module Import -M : This option imports a module. -Mmodule is the same has use module .
- 14. $> perl –Mdiagnostics script.pl Get better error message.
- 15. perl -MLWP::Simple -e 'print get($ARGV[0]), "\n"' http://perl.com Better as an alias.
- 16. -n: Looping -n : Perl assumes the following loop around your program: LINE: while (<>) { # Your code }
- 17. -n: Looping The command $> perl -ne 'print "$. - $_"' in.txt Would become LINE: while (<>) { print "$. - $_" } This code prints each line of the file together with the current line number.
- 18. -p: Looping with print -p : Perl assumes the following loop around your program: LINE: while (<>) { # your code goes here } continue { print or die "-p destination: $!\n"; } This uses a continue block on a while loop to ensure that the print statement is always called.
- 19. -p: Looping with print The -n example $> perl -ne 's/PHP/Perl/g; print' in.txt
- 20. or the simpler $> perl -pe ' s/PHP/Perl/g ' in.txt
- 21. It's very common to see command line programs that use Unix I/O redirection like this: $> perl -pe 's/PHP/Perl/g' in.txt > out.txt
- 22. -i: edit in place $> perl -i -pe 's/PHP/Perl/g' in.txt Substitute every PHP occurence by Perl
- 23. -i[extension] : edit in place. Case extension exists the original file is renamed, otherwise the file is overwitten.
- 24. If the extension doesn't contain a * , then it is appended to the end of the current filename. If the extension does contain one or more * characters, then each * is replaced with the current filename.
- 25. -l: Line-ending processing -l[octnum] : Automatic line-ending processing.
- 26. It assigns $\ to have the value of octnum . Without octnum, $\ will be assigned to $/ .
- 27. After chomp() everything on input
- 28. Adds $\ (the output record separator) to each print
- 29. -a and -F: Autosplitting -a: Splits the $_ whith a space while (<>) { @F = split(' '); # your code }
- 30. -F: choses a diferent separator
- 31. perl -F, -ane 'print join "\t", @F' data.csv converts a csv into a tsv. Not really true but enough for example propose.
- 33. Q&A