UNIX for Advanced & Expert Users

Hi,

Using the egrep ,i can exclude header and trailer records in file.I want to do in perl.Please help

egrep -iv 'head|trail' filename


Thanks in advance
MR

if you are reading a file in a perl script, and want to exclude some part of it (header and trailer) from processing, then there is no need to invoke an external program such as egrep. you can exclude whatever part you want to with the help of perl systax. something like:

Code:

while(<FH>) {
    next  if (m/head/);     # Skip header
    next  if (m/trail/);    # Skip trailer
    # process this line
}

or better yet,

Code:

next if (m/(head|trail)/);    # Skip header and trailer

Hi,
Thanks for your reply.I want to do it in single command line


Thanks in advance
MR

Code:

perl -ne 'print unless /head|tail/' file

If your requirement is to make a one-liner, what's wrong with the egrep solution you had already?

Hi
Just want to know using perl.

This below one not working (printing blank lines only)

Code:

$file='ab.txt';
open(F,'ab.txt')|| die ("could not open file $file!");
while (<F>)
{
 chop;
@F=next if(m/(begin|end)/i);
print  "@F\n"
}

Thanks,
MR

next skips to the following iteration. It does not return a useful value, and especially not a list containing a line you don't want to skip.

Code:

$file='ab.txt';
open(F,$file)|| die ("could not open file $file: $!");  # note minor changes in this line, too
while (<F>)
{
  # chop;  # Don't chop if you don't specifically need the line to be without a newline
  next if(m/(begin|end)/i);
  print;
}

In case you want the current line in a variable, the diamond operator <F> puts the current input line in $_, not in @F (in scalar context). chop, print, and the regex matching operators etc. all operate on $_ by default, i.e. unless you specify another variable to use.

In list context, <F> returns a list containing all the (remaining) input lines from the file handle. Here's an example of using list context:

Code:

print grep { ! /begin|end/ } <F>;

That is, grep the list of lines returned by <F>, picking out the ones which don't match the regex, and print them.

@F is only used if you have autosplit (-a option) in which case it contains the fields that the line was split into (on whitespace, unless you override it with the -F option).

Hi era,
I am really thankfull to you


Thanks,
MR