Shell Programming and Scripting

Hi All,

What happens when a Pelr script is executed.??(Jus like in C/C++ we have several stages like preprocessing,assembling,complining ,linkin',loadin'...)

So similiarly In Perl we have something like compile pahse and run phase. but what exactly happens during its exec and what all intermediate files will be created/linked/loaded ?????

A walkthrough on this will be much appreciated. Thanks!!!

You've got something wrong here: preprocessing, assembling, compiling and linking are not part of the execution of any program, but necessary steps to create an executable file. Otherwise everyone would have to have the source code available at any time to run any program, including the daemons loaded when the system is booting.

Same with Perl scripts: when the interpreter is started, the complete script is loaded into memory, "compiled" (translated into byte-code), and then executed. No intermediary files necessary.

If you need a highly detailed explanation, I'd suggest taking a look at the Perl source itself.

Sorry, for my English here....... I also meant such stages are involved in creating an executable file only.

But if u take an C program ....it creates a file after assembling the code for compiler( which will involve lexical/synatx analyser).Hence intermediate files are very much required for a C program. like .asm,.obj,files.

So,I wanted to know wethaer PERL also has a similiar type of stages before creating an executable.

That's not quite true. The GCC C/C++ compilers, for example, have the neat -pipe option, where no intermediate files are created, but the result of one step is piped to the next.

But that aside, with Perl, just as with Python, Shell, Ruby, TCL, ... basically any scripting language out there, there are no intermediate files. The whole file is read into memory, translated to byte code in memory, and executed from memory. Besides, no scripting language creates an executable (unless you supply very specific command line options and know what you're doing).