Match pattern and Extract section from file

[pramodkh]

Hi All
Today only i joined this group. need ur help.
Here goes my question:

Is there any simple way to match for a particular pattern ( with start and end delimitters) and extract the matched section?

I am doing it reading the contents line by line and setting the flags. But this logic is becoming complex, as i need to match and extract based on certain conditions.

for ex:

#ifdef X
some code
#endif

#ifdef Y
somecode
#ifdef Z
somemorecode
#else
code that does not match condition
#endif
#endif

---------------------------------
from the above text, i have to extract sections between #ifdef and #endif.( and ofcourse #else in some cases)

let me know for any further explanation about the same.

thanks in adv
Pramod

[numberwhun]

Hi All
Today only i joined this group. need ur help.
Here goes my question:

Is there any simple way to match for a particular pattern ( with start and end delimitters) and extract the matched section?

I am doing it reading the contents line by line and setting the flags. But this logic is becoming complex, as i need to match and extract based on certain conditions.

for ex:

#ifdef X
some code
#endif

#ifdef Y
somecode
#ifdef Z
somemorecode
#else
code that does not match condition
#endif
#endif

---------------------------------
from the above text, i have to extract sections between #ifdef and #endif.( and ofcourse #else in some cases)

let me know for any further explanation about the same.

thanks in adv
Pramod

Well, considering this is a learning forum and not a script writing service, I am obligated to ask you what you have tried thus far.

Please post your code that you have tried, in the necessary code tags, and we will help guide you from there.

Regards,

Jeff

[eggi]

To get you started, you can extract elements from a perl match using parentheses on the left hand side and $ variables on the right

for instance

$string="what is it"
print "$string\n";
$string =~ /^.* (is) .*$/$1/;
print "$string\n";
 

first print should get you "what is it"
second print should just be "is"

Hope this helps get you started!

, Mike

[pramodkh]

Here is what i hav tried so far.

1. Get the C file contents into array
2. Read elements of array(i.e lines of file)
3. check if it matches with '#ifdef and #endif'
4. set the flags( ifdefflag and endifflag)
5. take actions accordingly ( i mean write contents of ifdef into a temp file excluding #ifedf and #endif)

This is becoming complex to include all conditions like ( to check for #else and nested #ifdef )

Let me know is there any simple solution to achieve this. flag setting doesnt seem to be so useful in some cases.

Thanks
Pramod

[numberwhun]

The pseudo code that you supplied is not your actual code. Please provide your code, surrounded by the necessary code tags, and we will try and help you.

Regards,

Jeff

[pramodkh]

Hi,

Here is the code...need to format and change some of the declarations.
let me know if you need anu further comments to understand the code.

# Global variable Declaration and  Initialization
my $ifdefflag = 0;
my $elseflag = 0;
my $endifflag = 0;
my $counter = 0;
my $flag=0;
my $ctrToLookForifdef = 0;
my @filecontents;
my @splititem;
my @compiler_switches =(A,B,C); #has list of compiler switches used with #ifdef
 
#### Open File for reading the contents
open FH, "source.c" or die "can not open source.c...$!";
while (<FH>) {
               @filecontents = <FH>;
}
#### Backing up source file using system command
`copy source.c source.bak`;
#### Create new file after refactoring
open NEWFH, ">source.c" or die "can not open source.c...$!";
 
### Read contents of array, Match for ifdef and set the flags
foreach my $item (@filecontents ){
               # Match for #ifdef tag and set the flag
    if($item =~m/#ifdef/) {    
        $endifflag = 0;
                                 # couter to track nested ifdef    
        $ctrToLookForifdef++;        
                                 ## splitting with space to check for valid compiler switch
        @splititem= split(" ", $item);
        foreach my $cs (@compiler_switches){
            chomp $cs;
            chomp $splititem[1];
            if( $splititem[1] eq $cs and ($ctrToLookForifdef == 1)){
                $ifdefflag = 1;
                $flag=0;
                last;
            }
            else {                
                $flag=1;
            }
        }
        next;
    }
    elsif( $item =~m/#endif/){    
        $ctrToLookForifdef--;
        if($ctrToLookForifdef == 0){
            $endifflag = 1;
            $ifdefflag = 0;
            $flag=0;
        }
        next;
    }
    else {
        if($flag==1){
            next;
        }        
        print NEWFH "$item";    
        next;
    }
    if($ifdefflag and $endifflag==0){
        print NEWFH "$item";    
    }
    if($elseflag and $flag){
        print NEWFH "$item";            
    }
    if($endifflag){
        $ifdefflag = 0;
        next;
    }
}
close FH;
close NEWFH;
###### end of the file
 

Regards
Pramod

[pramodkh]

Hi All,

Any updates on this post? let me know if you need any further details.
I am still waiting for replies.

Regards
Pramod