How to write to line1 of an exisitng file in perl

[jonathan184]

Hi I am trying to write a line to a file but i want it to write to line 1 of the file and push down what was on line 1.

The code below works but inserts the line to the bottom of the page and i need the line to append to line1.

Could somebody help me out on how to do do this please.

#!/usr/bin/perl
$| = 1;
 
opendir(DIR, ".") or die $!;
 
@files = readdir(DIR),"\n";
close(DIR);   
 
my $i = 1;    
 
foreach (@files) {
 
 
   @_ = open (APPEND, ">>$_") or die "$! error trying to append";
   print APPEND "MATERIAL_UOM|MATERIAL_NUM|MATERIAL_DESC|X_PLANT";
 
 $i++;     
 print "\n\n $_ Job is finished\n\n";  
 
};

[KevinADC]

like so much of perl, there is more than one way to do this, but using perls inplace editor makes this job quite easy.

#!/usr/bin/!perl
opendir(DIR, ".") or die $!;
my @files = readdir DIR;
close(DIR);   
{
   local @ARGV = @files;
   local $^I = '.bac';
   while (<>) {
      if ($. == 1) {  
         print "MATERIAL_UOM|MATERIAL_NUM|MATERIAL_DESC|X_PLANT\n"; 
      }
      print;
   }
}
print "all finished";
 

my concern though is these two lines:

opendir(DIR, ".") or die $!;
my @files = readdir DIR;

"." will be the current directory and reading all the files in the directory into the @files array might not be what you want to do. Use the above code at your own risk if you run it as-is. Because it will attempt to open every file in the array and prepend the new line into the file. If that is really what you want to do then fine, but make sure to run some tests on dummy files anyway so you are sure it works like you want.

[jonathan184]

Thank you for the script i am going to try this soon.

I just got one question
local $^I = '.bac'; does this mean it will add lines to *.bac files alone in the array?

about the read dir I put the . for testing when everything works good i will put the full path and the script in a different dir.

Thanks for your reply i really appreciate it.

[KevinADC]

I just got one question
local $^I = '.bac'; does this mean it will add lines to *.bac files alone in the array?

No. That line tells perl to make a backup copy of the original file and name the file with a .bac extension (you can choose any name for the extension). If the original were "log.txt" perl will make a backup copy of the original file named "log.txt.bac". If you're using a nix box and don't want a backup copy you can use:

$^I = '';

but if you are using a windows box you most likely will have to define the backup file extension otherwise windows throws an error and the script dies, but you can delete the backup file after editing the original file.

[KevinADC]

btw,

assigning the return value of the open function to the system array @_ isn't really doing anything.

@_ = open (APPEND, ">>$_") or die "$! error trying to append";

better written like this:

open (APPEND, ">>test.txt") or die "$! error trying to append";
print APPEND "MATERIAL_UOM|MATERIAL_NUM|MATERIAL_DESC|X_PLANT\n";
close(APPEND);
 

unless you were really planning on doing something with @_, but I can't imagine what?

[jonathan184]

When i run the script below i get an error, now i have the script at d:\\Documents and Settings\\peewee2\\Desktop\\load these\\jan18

and the files that need to have the line added is at d:\\Documents and Settings\\peewee2\\Desktop\\load these\\jan18\\backup\\

but when i run the script I got this message:

Can't open int_sap_contractcontact_180107_999082.txt: No such file or directory
at addline1.pl line 8.
Can't open int_sap_contractcontact_180107_999082.txt.bac: No such file or direct
ory at addline1.pl line 8.



When i checked line8 this is what i have on line 8

while (<>) {

Where do you think iam going wrong?

#!/usr/bin/!perl
opendir(DIR, "d:\\Documents and Settings\\peewee2\\Desktop\\load these\\jan18\\backup\\") or die $!;
my @files = readdir DIR;
close(DIR);   
{
   local @ARGV = @files;
   local $^I = '.bac';
   while (<>) {
      if ($. == 1) {  
         print "MATERIAL_UOM|MATERIAL_NUM|MATERIAL_DESC|X_PLANT\n"; 
      }
      print;
   }
}
print "all finished";

[KevinADC]

is the script itself on the 'c' drive? Try changing to the 'd' drive before openng the files for inserting the newline:

chdir('d:\\') or die "$!";

or change ino the directory where the files are stored.