#+TITLE: Study Note
#+AUTHOR: Peng Li
#+EMAIL: seudut@gmail.com
#+DATE: 2016-08-18

* Programming Languages
** gnuplog

1. normal
#+BEGIN_SRC gnuplot :exports code :file ./temp/sin.png
  reset
  plot sin(x)/x
#+END_SRC

#+RESULTS:
[[file:./temp/sin.png]]

2. plot with data file
#+BEGIN_SRC 

#+END_SRC


* Perl One Line Command
#+BEGIN_SRC sh :exports both :results output replace
  perl --help
#+END_SRC

#+RESULTS:
#+begin_example

Usage: perl [switches] [--] [programfile] [arguments]
  -0[octal]         specify record separator (\0, if no argument)
  -a                autosplit mode with -n or -p (splits $_ into @F)
  -C[number/list]   enables the listed Unicode features
  -c                check syntax only (runs BEGIN and CHECK blocks)
  -d[:debugger]     run program under debugger
  -D[number/list]   set debugging flags (argument is a bit mask or alphabets)
  -e program        one line of program (several -e's allowed, omit programfile)
  -E program        like -e, but enables all optional features
  -f                don't do $sitelib/sitecustomize.pl at startup
  -F/pattern/       split() pattern for -a switch (//'s are optional)
  -i[extension]     edit <> files in place (makes backup if extension supplied)
  -Idirectory       specify @INC/#include directory (several -I's allowed)
  -l[octal]         enable line ending processing, specifies line terminator
  -[mM][-]module    execute "use/no module..." before executing program
  -n                assume "while (<>) { ... }" loop around program
  -p                assume loop like -n but print line also, like sed
  -s                enable rudimentary parsing for switches after programfile
  -S                look for programfile using PATH environment variable
  -t                enable tainting warnings
  -T                enable tainting checks
  -u                dump core after parsing program
  -U                allow unsafe operations
  -v                print version, patchlevel and license
  -V[:variable]     print configuration summary (or a single Config.pm variable)
  -w                enable many useful warnings
  -W                enable all warnings
  -x[directory]     ignore text before #!perl line (optionally cd to directory)
  -X                disable all warnings
  
Run 'perldoc perl' for more help with Perl.

#+end_example

1. Used as =grep=
#+BEGIN_SRC sh
  perl -ne 'print if /expression/' xxx.log;
#+END_SRC

Or 
#+BEGIN_SRC sh
  perl -wnl -e '/keyword/ and print;' xxx.log
#+END_SRC


2. Used as =awk=
#+BEGIN_SRC sh
  perl -ne 'print "$1\n" if /aaa=(\d+)\s.*/' xxx.log;
#+END_SRC

3.
#+BEGIN_SRC sh
  perl -pe 'some code' < input.txt > output.txt
#+END_SRC