17

I have a unix command that does the following:

head -c 2048 > test.txt

basically its taking first 2kb of the test.txt file.

Can we do something similar in windows cmd prompt?

4
  • thank you guys for all your awesome replies..@sonjz I have a text file with one long string of hex dump..how can i use your code to extract only 2kb worth of data from it?? I tried your code but its still extracting the whole hex dump..thanks..i will upload the text file file for you..
    – plasma33
    Jan 3, 2015 at 5:41
  • please find the link here-> dropbox.com/s/h29mdg0t8df8i1e/test.txt?dl=0
    – plasma33
    Jan 3, 2015 at 5:52
  • @ sonjz: how to use "Get-FileHex" to extract 2kb of hex data using powershell..do you know about this function??
    – plasma33
    Jan 3, 2015 at 6:21
  • you want to extract byte array. The following code will yank 2KB and write to a new file: $byteArray = Get-Content binary.bin -Encoding Byte -TotalCount 2KB; [io.file]::WriteAllBytes('c:\binary.bin', $byteArray)
    – sonjz
    Jan 6, 2015 at 1:03

3 Answers 3

19

Simplifying this answer because of @chubbsondubs' comment.

-TotalCount will count lines if reading in text, so always force it to read the file as bytes, then the -TotalCount will only refer to bytes and you can get an account count.

Get-Content test.txt -Encoding byte -TotalCount 2KB | Set-Content test1.txt -Encoding byte

More information here: https://stackoverflow.com/questions/888063/powershell-to-get-the-first-x-mb-of-a-file

5
  • This gets the first 2048 lines not bytes of the file. TotalCount takes the number of lines you want. Jun 26, 2018 at 14:40
  • @chubbsondubs yup, i see the issue now, you always have to encode and decode in bytes, i'll update the answer
    – sonjz
    Jun 27, 2018 at 1:11
  • this is not the command prompt, its powershell
    – user32882
    Mar 9, 2019 at 4:54
  • 1
    Question was for "command line", both command prompt and PowerShell are command line shells for Windows. Command prompt being the archaic "stop using this" one.
    – sonjz
    Mar 10, 2019 at 22:07
  • This doesn't work in Powershell 6. In order for it to work, you must replace -Encoding byte with -AsByteStream
    – Omid
    Mar 18, 2020 at 19:59
3

From what I can tell you can't print out by size in a native way; there is the type command which will output a whole text file, but you can't specify how much you want to output.

There is also the more command, which will allow you to print out lines of a file. These are some of the flags from more /?:

/E      Enable extended features
/C      Clear screen before displaying page
/P      Expand FormFeed characters
/S      Squeeze multiple blank lines into a single line
/Tn     Expand tabs to n spaces (default 8)

        Switches can be present in the MORE environment
        variable.

+n      Start displaying the first file at line n

files   List of files to be displayed. Files in the list
        are separated by blanks.

If extended features are enabled, the following commands
are accepted at the -- More -- prompt:

P n     Display next n lines
S n     Skip next n lines
F       Display next file
Q       Quit
=       Show line number
?       Show help line
<space> Display next page
<ret>   Display next line

If neither of these work for you, you can alternatively install Cygwin and you can use cat or head.

4
  • cygwin also has the 'head' command if you choose to use that option Jan 3, 2015 at 3:41
  • @JeffClayton Shoot.. you're right, for some reason I was thinking cat instead of head
    – cutrightjm
    Jan 3, 2015 at 3:43
  • 'cat' is the unix command that matches up to the 'type' command in windows, since you were discussing 'type' it only makes sense. Jan 3, 2015 at 3:45
  • Question is asking to process bytes in file, not lines
    – Zimba
    Mar 25, 2021 at 23:18
1

To keep first 2048 bytes of test.txt:

FSUTIL file seteof test.txt 2048

To keep a copy of test.txt, make a copy of it first.

Tested in Win 10

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