Learning perl (Start with basics & Hello world)

On August 13, 2009, in linux, linux programming, by mahesh
2


Introduction
Perl is a interpreted language. It is almost available in all popular operating systems today. Perl will be similar to C language and awk.

Basics

  • Perl script file mostly will have the extension .pl
  • In unix and Linux flavours, the perl file should have an execution permission.
  • Start the perl script file with #!/usr/bin/perl
  • Dont forget to terminate perl commands with ; (semicolen). eg., print “Hello world\n”;

program 1

Always the first program I try on any language is hello world, so perl’s hello world program is here for Linux and UNIX flavours,

#!/usr/bin/perl
print "Hello world.\n";

In Windows the same program will look like,

#!D:/perl/perl.exe
print "Hello world.\n";
  • The first line (in both examples) is a comment for perl, but for shell it tells which interpriter in what path to use on the file.
  • The second command print is similar to printf in C language with some difference. Lets learn the difference later.

Output

perl_hello_world

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mouse scroll in vim

On May 12, 2009, in linux, linux commands, by mahesh
0


The vim editor has lot features be explored, it takes mouse scroll events and allows the content to be scrolled. This post will be incomplete as I discuss only scrolling in xterm, but will update periodicalling on other terminals also.

For xterm, to add mouse scroll support to vim use the following command.
set mouse=a

For putty terminal, from windows use
set ttymouse=xterm2

To type the above command in vim type shift+; then the command

Add the command to ~/.vimrc to add scrolling by default

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alias (linux command)

On May 11, 2009, in linux, linux administration, linux commands, by mahesh
0


alias – Create alias name for a command.

Summary
alias is Bash build-in command. This is very useful to create a simple
alias for a complex/long/frequent commands. Once alias created, you
can use alias to call the original command. This alias are deleted
after closing the shell session. For the next session, you have create
it again. So to avoid this problem, you add it in your .bashrc file.

Example
$ alias — Prints all alias commands

$ alias cls=clear — Alias for new user from DOS world.

$ alias ls=”ls -F –color=always” — Alias long ls command.

$ alias mycd=’cd a/b/c/d/e/f/h’ — Shortcut for long CD.

$ alias ls — Print the alias’ original command.

$ \ls – Skip alias and run the original command.

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