Perl – File Read Write
Example
In this post, let’s see how
to remove the new line character or line break in a text file and save the
result in another text file.
Refer to other posts File
handling, RegEx.
To accomplish the removal of
new line character, we use RegEx substitution
operator. The code for substitution is as below,
$a
=~ s/\n//; # $a is the variable in
which the replacement takes place
·
The input
to the script is through command line arguments. The command line inputs are
stored in the array variable @ARGV
(please note the CAPS). First we check the size. If no command line arguments is
specified, the size of ARGV is -1. If so, the script prints the usage &
exits, using the in-built function die().
unless($#ARGV
<0) {
$in_file=$ARGV[0];
}
else {
die "\nUsage:\n remove_new_line.pl <input_file>\n";
}
·
If valid
input is provided, then open the specified file in read mode as below. If unable
to open the file, exit with a note printed.
$! Is the Perl system
variable which prints the error from the OS.
open FIN,
"<$in_file" or die "Unable to read '$in_file' :$!";
·
Create
the output file by appending the name “new_” to the input file
name.
open
FOUT, ">new_$in_file" or die "Unable to create
'new_$in_file' :$!";
·
Then
create a loop, that executes for each line of the input
file. Then remove the newline character and write back the result to output
file.
while
($a=<FIN>) {
# remove \n character
$a =~ s/\n//;
# write the new data to text
file
print FOUT $a;
}
Sample output of this
script:
Top file is the input & bottom
file is the output.
