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Home: Perl Programming Help: Beginner:
Read a file from a specific line and extract something to another file

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sfo_sc
Novice

Jan 19, 2005, 9:08 PM

Post #26 of 33 (7977 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

Whats wrong with this piece of code? I couldn't figure out.

Code

while($file[$i] =~ m/^\t/ || $file[$i] =~ m/^Caused/ 
	|| length($file[$i]) == 0 || $file[$i] =~ m/^\s/) { 
    push(@temp, $file[$i] . "\n"); 
    $i++; 
}

I keep getting "Use of uninitialized value in pattern match (m//) at ./logwatch.pl line 53, <SOURCE> line 274." and go into infinit loop. Please help.

It is complaining about the leading whitespace condition I just adding. If I remove that, the code will work.

Line 53 is the $i++, which doesn't make sense at all.

Here is the case where I want to capture to the file.

Code

java.lang.InternalError: jzentry == 0, 
 jzfile = 135272768, 
 total = 390, 
 name = /opt/tomcat5/webapps/fsm.war, 
 i = 12, 
 message = invalid LOC header (bad signature) 
	at java.util.zip.ZipFile$2.nextElement(ZipFile.java:320)

I can capture the line start with tab no problem, but I couldn't get the lines start with space.

(This post was edited by sfo_sc on Jan 19, 2005, 10:53 PM)

KevinR
Veteran

Jan 19, 2005, 10:35 PM

Post #27 of 33 (7970 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

In Reply To

Thanks for the info. I found out I can use length($string) == 0 too. =)

but when I try to look for lines that start with space and I use m/^\s/, the code will go into infinit loop.

Can you post an example of the code you are trying, because

Code

if ($string =~ /^\s/) { 
  do something 
}

should find lines that start with a space or a tab
-------------------------------------------------

sfo_sc
Novice

Jan 19, 2005, 10:50 PM

Post #28 of 33 (7968 views)

Re: [KevinR] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

Darn it! Figure out why. It is totally un-related to the regular expression. Took me whole day to figure it out. Thank you for your help KevinR

(This post was edited by sfo_sc on Jan 19, 2005, 11:21 PM)

sfo_sc
Novice

Jan 19, 2005, 11:35 PM

Post #29 of 33 (7961 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

In Reply To

Whats wrong with this piece of code? I couldn't figure out.

Code

while($file[$i] =~ m/^\t/ || $file[$i] =~ m/^Caused/ 
	|| length($file[$i]) == 0 || $file[$i] =~ m/^\s/) { 
    push(@temp, $file[$i] . "\n"); 
    $i++; 
}

Code

java.lang.InternalError: jzentry == 0, 
 jzfile = 135272768, 
 total = 390, 
 name = /opt/tomcat5/webapps/fsm.war, 
 i = 12, 
 message = invalid LOC header (bad signature) 
	at java.util.zip.ZipFile$2.nextElement(ZipFile.java:320)

I can capture the line start with tab no problem, but I couldn't get the lines start with space.

My code magically works if I add another line at the end of the read in file which doesn't match any of the case. So if my read file ends with a line that matches the case, my code will go into infinit loop. Can someone see whats wrong with my code? What is causing the problem?

sfo_sc
Novice

Jan 19, 2005, 11:38 PM

Post #30 of 33 (7960 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

I think I found the problem. Crazy

I better go get some sleep to clear up my mind.

KevinR
Veteran

Jan 20, 2005, 12:10 AM

Post #31 of 33 (7959 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

I think maybe you want to use "if" instead of "while" here:

Code

while ($file[$i] =~ m/^\t/ || $file[$i] =~ m/^Caused/  
	|| length($file[$i]) == 0 || $file[$i] =~ m/^\s/) {  
    push(@temp, $file[$i] . "\n");  
    $i++;  
}

"while" is generally used for looping through lists or files while a condition is true. "if" is used to make a decision based on the evaluation of an expression.

what you have is something like this:

Code

$num = 1; 
while ($num == 1) { 
   print "AHHHH!!"; 
}

since $num will always equal 1, the condition will always be true, and the loop will never exit. Now go get some sleep! Wink

-------------------------------------------------

(This post was edited by KevinR on Jan 20, 2005, 12:13 AM)

sfo_sc
Novice

Jan 20, 2005, 1:14 PM

Post #32 of 33 (7948 views)

Re: [KevinR] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

Something I have learn since I was studying Computer Science, once my head really gets stuck, it is usually time to go to bed! Tongue

Jean
User

Jan 23, 2005, 10:15 AM

Post #33 of 33 (7935 views)

Re: [sfo_sc] Read a file from a specific line and extract something to another file [In reply to]	Can't Post

I'm not sure why the code would go into infinite loop, but this can help you:

\s matches tabs as well as other whitespace, e.g. ascii(32)

Jean Spector
SQA Engineer @ Exanet
jean.spector@softhome.net

There are only 10 types of people in the world -
Those who understand binary, and those who don't.

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