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100 lines
2.8 KiB
Plaintext
100 lines
2.8 KiB
Plaintext
-> Perl is weakly typed language.
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$a=10;
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$b="a";
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$c=$a.$b;
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print $c;
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output:
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10a
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-> It follows both procedural and object oriented paradigm.
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Ex: Csc01BuildUnit.pm -> Base class = Build.pm
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^ ^
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Derived class Base class
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With .pm extension is for perl module
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-> Perl is interpreted language, but as compare to interpreted language like
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bash, etc, perl can be compiled to bytecode.
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-> Perl can support .pl or .PL extension, but not restricted to these only
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can also use .pm extension, which used in Tejas Networks.
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-> '#!/usr/bin/env perl':
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Will search for perl in $PATH environment variable from shell and then run from
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that
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The path mentioned is path for binary 'env' which is used to find
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exectuable for perl
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Use command 'which perl' to find the location of perl
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-> '#!/usr/bin/perl':
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This will be used in direct path for perl exectuable( absence of this
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can lead to error.)
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flags:
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-d: debugging mode(suboption: next, run, step, print, etc).
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* h: help
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* run: start execution
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* next: next line
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* step: follow function call if there
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* print: non-nested printing
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* x: nested printing of objects, data structures, etc
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* b: set break points
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* c: continue
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-I Directory: (include directory): Specifies @INC
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It add specific directories to @INC array
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-w: Shows important warnings
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-W: Shows all warnings
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-X: Disable all warnings
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@INC: It is a array of include directory.
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While running the scripts, we might see this in error logs.
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This means that some include directories are missing.
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-> -e "program": Runs perl script sent in as a program(Interactive mode
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programming). To run a one liner perl command use -e flag
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perl -e 'print "Hello World\n"'
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Output: Hello World
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-> eval perl: To run multi line perl command use eval perl.
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For example:
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eval perl
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@a = ('csc01', 'csc02', 'cef8');
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print @a, "\n";
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print "@a\n";
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CTRL+D
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-> -t && -T && -U: For security & taint check/warnings.
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* -T: check for unsecure operation tainting in given perl script
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and treat them as fatal errors. Stop the scripts
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* -t: small brother of -T, run the scripts with warnings
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* -U: Allow unsecure and run scripts without warnings and errors.
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-> Comments:
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Begins with '#' symbol.
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'#' is used for single line comment.
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Multi-line comment is achieved using:
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=begin
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.....
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comments
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.....
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=cut
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exception:
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'#!/usr/bin/perl' Shabang is not comment. It just tell
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the bash that its a perl script. |