Perl In The Command Line
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Perl In The Command Line






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Perl In The Command Line Perl In The Command Line Presentation Transcript

  • Perl in the Command Line
  • -c: Test Compiling
    • -c : causes Perl to check the syntax of the program and then exit without executing it.
    • It will execute BEGIN , UNITCHECK , CHECK , and use blocks, because these are considered as occurring outside the execution of your program.
    • It will not execute INIT and END blocks.
  • -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 The -w option has been replaced by the use warnings pragma.
    • -W: Enables all warnings regardless of no warnings or $^W .
    • -X: Disables all warnings regardless of use warnings or $^W .
    • $> perldoc perllexwarn
  • -d: Debugging
    • -d : This option puts you into the Perl debugger.
    • -d:DProf : executes the program using the Devel::DProf profiler, combined with dprofpp may help you to find where is your program slow.
    • $> perldoc perldebtut $> perldoc perldebug
  • -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
  • -M: module Import
    • -M : This option imports a module. -Mmodule is the same has use module .
    • $> perl –Mdiagnostics Get better error message.
    • perl -MLWP::Simple -e 'print get($ARGV[0]), " "' Better as an alias.
  • -n: Looping
    • -n : Perl assumes the following loop around your program: LINE: while (<>) { # Your code }
  • -n: Looping
    • The command $> perl -ne 'print &quot;$. - $_&quot;' in.txt Would become LINE: while (<>) { print &quot;$. - $_&quot; } This code prints each line of the file together with the current line number.
  • -p: Looping with print
    • -p : Perl assumes the following loop around your program: LINE: while (<>) { # your code goes here } continue { print or die &quot;-p destination: $! &quot;; } This uses a continue block on a while loop to ensure that the print statement is always called.
  • -p: Looping with print
    • The -n example $> perl -ne 's/PHP/Perl/g; print' in.txt
    • or the simpler $> perl -pe ' s/PHP/Perl/g ' in.txt
    • 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
  • -i: edit in place
    • $> perl -i -pe 's/PHP/Perl/g' in.txt Substitute every PHP occurence by Perl
    • -i[extension] : edit in place. Case extension exists the original file is renamed, otherwise the file is overwitten.
    • 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.
  • -l: Line-ending processing
    • -l[octnum] : Automatic line-ending processing.
    • It assigns $ to have the value of octnum . Without octnum, $ will be assigned to $/ .
    • After
      • chomp() everything on input
      • Adds $ (the output record separator) to each print
  • -a and -F: Autosplitting
    • -a: Splits the $_ whith a space while (<>) { @F = split(' '); # your code }
    • -F: choses a diferent separator
    • perl -F, -ane 'print join &quot; &quot;, @F' data.csv converts a csv into a tsv. Not really true but enough for example propose.
    • $> perldoc perlrun
  • Q&A