perl - How to modify content of a file using single file handle -

i'm trying modify content of file using perl.

the following script works fine.

#!/usr/bin/perl  use strict; use warnings;  open(fh,"test.txt") || die "not able open test.txt $!"; open(fh2,">","test_new.txt")|| die "not able opne test_new.txt $!";  while(my $line = <fh>) {         $line =~ s/perl/python/i;         print fh2 $line; } close(fh); close(fh2); 

the content of test.txt:

im learning perl im in file handlers chapter 

the output in test_new.txt:

im learning python im in file handlers chapter 

if try use same file handle modifying content of file, i'm not getting expected output. following script attempts this:

#!/usr/bin/perl  use strict; use warnings;  open(fh,"+<","test.txt") || die "not able open test.txt $!";  while(my $line = <fh>) {         $line =~ s/perl/python/i;         print fh $line; } close(fh); 

incorrect output in test.txt:

im learning perl im learning python  chapter  chapter 

how modify file contents using single file handle?

as @Сухой27 answered

it's typical situation perl onliner pleasingly used.

perl -i -pe 's/perl/python/i'

perl takes below options

• -p : make line line loop(every line assign $_ , print after evaluated $_)
• -e : evaluate code block in above loop ( regex take $_ default operand )
• -i : in plcae file edit (if pass arguments -i, perl preserve original files extention)

if run below script

perl -i.bak -pe 's/perl/python/i' test.txt

you modified test.txt

im learning python im in file handlers chapter 

and original text files named in test.txt.bak

im learning perl im in file handlers chapter