How do I delete the first n characters on a line

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Re: how do i delete the first n characters on a line by jmcnamara (Monsignor) on Jul 18, 2001 at 12:28 UTC
Use substr: `# substr EXPR,OFFSET,LENGTH,REPLACEMENT my $n = 3; my $str1 = "1234567890\n"; my $str2 = substr($str1, $n); print $str1; # 1234567890 print $str2; # 4567890` [download] John. --	[reply] [d/l]
Re: How do I delete the first n characters on a line by ar0n (Priest) on Jul 18, 2001 at 12:28 UTC
`substr($str, 0, $n) = "";`	[reply] [d/l]
Re: How do I delete the first n characters on a line by tachyon (Chancellor) on Jul 19, 2001 at 05:43 UTC
You could also use a regex although this is not as fast as substr. `my $n = 3; my $str = "1234567890\n"; $str =~ s/^.{$n}//s; # was: $str =~ s/^.{$n}(.*)$/$1/s; print $str;` [download] The difference with the regex solution is that if $n > length $str no change will be made. With substr you will get a null string left in $str if you try to delete more chars than exist in $str. You need the /s modifier to make the . match a newline which is a valid char. cheers tachyon To get the same behavior as a substr solution use: `$str =~ s/^.{1,$n}//s;` Edit by tye to incorporate I0's reply	[reply] [d/l] [select]
Re: Answer: How do I delete the first n characters on a line by I0 (Priest) on Jul 20, 2001 at 03:37 UTC
#a simpler regex is `$str =~ s/^.{$n}//s` #or, if you want a null string left in $str if you try to delete more chars than exist in $str, `$str =~ s/^.{1,$n}//s`	[reply] [d/l] [select]
Re: How do I delete the first n characters on a line by abstracts (Hermit) on Jul 19, 2001 at 06:26 UTC
# substr EXPR,OFFSET,LENGTH,REPLACEMENT my $n = 3; my $str1 = "1234567890\n"; print $str1; # 1234567890 substr($str1,0,$n,''); print $str1; # 4567890 Aziz,,, Originally posted as a Categorized Answer.	[reply]
Re: How do I delete the first n characters on a line by bikeNomad (Priest) on Jul 19, 2001 at 07:13 UTC
Another interesting thing about substr is that it can be assigned to (it's an lvalue). So if you really wanted to delete the characters, you could do this: `my $line = "abcdefghijk"; # delete the first 3 characters: substr($line, 0, 3) = ''; print $line; # "defghijk"` [download] Originally posted as a Categorized Answer.	[reply] [d/l]
Re: How do I delete the first n characters on a line by Anonymous Monk on Jul 19, 2001 at 16:37 UTC
regexes carry with them a performance penalty. there is nothing wront with just: `$foo = substr($foo,$n) unless(length $foo => $n);` [download] or `$substr($foo,0,$n)="" unless(length $foo => $n);` [download] or `$substr($foo,0,$n,'') unless(length $foo => $n);` [download] this is generally faster than a regex ;-) Originally posted as a Categorized Answer.	[reply] [d/l] [select]
Re: How do I delete the first n characters on a line by alfie (Pilgrim) on Jul 18, 2001 at 12:28 UTC
Given that you have the line in `$_` and substitute the n with the amount of characters you'd like to delete: `s/^.{n}//;` [download] Originally posted as a Categorized Answer.	[reply] [d/l] [select]