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Top Forums Shell Programming and Scripting Displaying the first field if the second field matches the pattern using Perl Post 302727205 by elixir_sinari on Tuesday 6th of November 2012 02:12:51 AM
Old 11-06-2012
Quote:
Originally Posted by royalibrahim
I Just want to understand whether in Perl, is it possible to iterate over a file object using a for loop as I did in my code? Perl complains no error even if you use it.
Of course, yes. You did it, right?

Why would perl complain when what you were doing was syntactically correct but logically wrong?

Never use a for (or foreach) loop to read a file. In this case, all lines from the file (depending on the input record separator) will be read in at once and stored in memory to form a list. Your loop will then iterate over the elements of this list. So, you might hit your system's memory limits.

A while loop is much much better as it reads one record at a time.
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MEWL(1) 						      General Commands Manual							   MEWL(1)

NAME
mewl - Message scanner for Mew 4 or later SYNOPSIS
mewl [options] [folder [range]] DESCRIPTION
The mewl utility extracts necessary fields from messages stored in folders. This command is necessary for Mew to implement the asynchro- nous feature. The options are as follows: -a Print all necessary fields when picking. -b dir Set the Mail home to dir. -c bodylen Set the max body length to be extracted to bodylen. -d field Set the field to be extracted to field. -e command Specify an external command to fetch mailbox. -m options Specify options for command. -f fields Specify fields to display. -h Display this help message. -i file Set the input stream to file. -l length Set the max field length to be extracted to length. The default value is 3. 0 means no limit. -n Don't use fstat(). -p pattern Specify the pick pattern. -s src Set message source to src : '+folder range'. -w Wait for stdio input to synchronize. -v Display the version. -x suffix Use this suffix. Definitions of the symbols above are as follows: range N | [start]-[end] | last:N pattern 'key=val' | 'key!=val' | '!<pattern>' | '(<pattern>)' | '<pattern>&<pattern>' | '<pattern>|<pattern>' BUGS
If a field is long, only the beginning three lines are extracted by default. March 5, 2003 MEWL(1)
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