delete first n lines from a file

[babhuko]

hi all,

can someone help me in writing a batch program, which deletes first n lines from a file and place the remaining content in a new file.

thanks in advance.

[Squashman]

Code: [Select]

FOR /F "skip=5 tokens=* delims=" %%G in (Myfile.txt) do echo %%G>>NewFile.txt

[jimschel]

If you till tell me the maximum length of the a line, I can make you a quick program that will let you enter the number of lines to skip and then willl copy the rest of the file.

[Squashman]

If you till tell me the maximum length of the a line, I can make you a quick program that will let you enter the number of lines to skip and then willl copy the rest of the file.

That seems kind of limited if you ask me.
Granted the cmd processor is limited to 8192 bytes to assign to a variable but what are the odds of the lines being that long.

[Dusty]

A For loop will probably not copy blank lines.   Use the More command with the +n switch.

[Salmon Trout]

A For loop will probably not copy blank lines.

Or ones starting with a space or semicolon, I think. And poison characters will stop the script dead.

[Squashman]

Barring any line starting with a colon this will work.  I can change the code as well if the file has a line that starts with a colon.
Input

Code: [Select]

Line:1
Line:2
Line:3
Line:4
Line:5
Line:6 next line is blank

Line:8 next line has special characters
#!@#$%^&*()+<>"':!%%!
Line:10Script

Code: [Select]

@echo off

for /f "skip=5 tokens=1* delims=:" %%G in ('type "myfile.txt" ^| findstr /n "^"') do echo.%%H>>myfile_new.txtOutput

Code: [Select]

Line:6 next line is blank

Line:8 next line has special characters
#!@#$%^&*()+<>"':!%%!
Line:10

[Dusty]

Keeping to the KISS principle:

Code: [Select]

more +n myfile.txt > newfile.txt

[Squashman]

Keeping to the KISS principle:

Code: [Select]

more +n myfile.txt > newfile.txt

As far as I can tell that will not work if the number of lines in the files exceeds 65,534.  Which most of mine do. I do data processing for a living. On the 65,535 line it outputs -- More (4%) -- to the output file and the batch file pauses.

[Salmon Trout]

As far as I can tell that will not work if the number of lines in the files exceeds 65,534.  Which most of mine do.

skipline.vbs

Code: [Select]

Const ForReading = 1
Const ForWriting = 2
Set objFSO = CreateObject("Scripting.FileSystemObject")
ReadFileName  = wscript.arguments(0)
LinesToSkip   = wscript.arguments(1)
WriteFileName = wscript.arguments(2)

' for demo purposes; can delete
'--------------------------------------
StartRead = Timer
'--------------------------------------

Set ReadFile  = objFSO.OpenTextFile (wscript.arguments(0),  ForReading)
strText = ReadFile.ReadAll
Readfile.Close

' for demo purposes; can delete
'--------------------------------------
EndRead = Timer
ReadTime = EndRead - StartRead
StartSplit = Timer
'--------------------------------------

ArrayOfLines = Split(strText, vbCrLf)

' for demo purposes; can delete
'--------------------------------------
Endsplit = Timer
SplitTime = Endsplit - StartSplit
StartWrite = Timer
'--------------------------------------

Set Writefile = objFSO.CreateTextFile (WriteFileName, ForWriting)
For j = LinesToSkip To UBound(ArrayOfLines)
Writefile.writeline ArrayOfLines(j)
Next
Writefile.Close

' for demo purposes; can delete
'--------------------------------------
EndWrite = Timer
TotalTime = EndWrite - StartRead
WriteTime = EndWrite - StartWrite
wscript.echo "Number of Lines in file: " & UBound(ArrayOfLines)
wscript.echo "Read file in             " & ReadTime  & " sec(s)"
wscript.echo "Split file in            " & SplitTime & " sec(s)"
wscript.echo "Wrote output file in     " & WriteTime & " sec(s)"
wscript.echo "Total time taken         " & TotalTime & " sec(s)"
'--------------------------------------


Code: [Select]

C:\Batch\Test\>type 20lines.txt
This is line 1
This is line 2
This is line 3
This is line 4
This is line 5
This is line 6
This is line 7
This is line 8
This is line 9
This is line 10
This is line 11
This is line 12
This is line 13
This is line 14
This is line 15
This is line 16
This is line 17
This is line 18
This is line 19
This is line 20

C:\Batch\Test\>cscript.exe //nologo skipline.vbs "20lines.txt" 3 "outlist.txt"
Number of Lines in file: 20
Read file in             0 sec(s)
Split file in            0 sec(s)
Wrote output file in     0.0078125 sec(s)
Total time taken         0.0078125 sec(s)

C:\Batch\Test\>type outlist.txt
This is line 4
This is line 5
This is line 6
This is line 7
This is line 8
This is line 9
This is line 10
This is line 11
This is line 12
This is line 13
This is line 14
This is line 15
This is line 16
This is line 17
This is line 18
This is line 19
This is line 20


Note: the load and split times for the small file are too short for the VBScript timer function to measure.

Now for some real files...

Clist.csv has nearly 300,000 lines like this and is 36 MB in size

"CreationTime","Length","FullName"
"04/06/2011 08:43:43","4226277376","C:\pagefile.sys"
"02/06/2011 21:08:43","3169705984","C:\hiberfil.sys"
"05/03/2011 08:14:10","2376366352","C:\Documents and Settings\Mike\X15-65732.iso"
"05/03/2011 08:14:10","2376366352","C:\Users\Mike\X15-65732.iso"
"07/07/2011 20:39:09","1818939392","C:\Users\Mike\AppData\Local\Microsoft\Windows Virtual PC\Virtual Machines\Windows XP Mode.vhd"
"07/07/2011 20:39:09","1818939392","C:\Documents and Settings\Mike\AppData\Local\Microsoft\Windows Virtual PC\Virtual Machines\Windows XP Mode.vhd"

Code: [Select]

C:\Batch\Test\>cscript.exe //nologo skipline.vbs "Clist.csv" 3 "outlist.txt"
Number of Lines in file: 294457
Read file in             1.953125 sec(s)
Split file in            0.6328125 sec(s)
Wrote output file in     3.632813 sec(s)
Total time taken         6.21875 sec(s)
Big-Clist.csv has nearly a million lines and is 108 MB in size

Code: [Select]

C:\Batch\Test\>cscript.exe //nologo skipline.vbs "Big-Clist.csv" 3 "outlist.txt"
Number of Lines in file: 883371
Read file in             5.164063 sec(s)
Split file in            5.390625 sec(s)
Wrote output file in     10.95313 sec(s)
Total time taken         21.50781 sec(s)
System: AMD Phenom II 3.0  GHz 4 GB RAM drive: 7200 rpm SATA

[Squashman]

Nice Job. Vbscript has always been one of those things I have just refused to learn.

[Salmon Trout]

In my script above, is this:

Code: [Select]

Set ReadFile  = objFSO.OpenTextFile (wscript.arguments(0),  ForReading)
That will work, but for consistency it should be

Code: [Select]

Set ReadFile  = objFSO.OpenTextFile (ReadFileName,  ForReading)

Vbscript has always been one of those things I have just refused to learn.

It's not all that hard, especially if you can use it to do useful things, and it can do so much more than batch. Of course Powershell is the way to go nowadays...

[Squashman]

I started pushing myself to use Powershell 2 years ago and then I went on vacationand when I got back to work I said screw it. But it made me realize that object oriented programming is pretty awesome. I was even making gui's with my Powershell scripts.