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?
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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..– plasma33Jan 3, 2015 at 5:41
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please find the link here-> dropbox.com/s/h29mdg0t8df8i1e/test.txt?dl=0– plasma33Jan 3, 2015 at 5:52
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@ sonjz: how to use "Get-FileHex" to extract 2kb of hex data using powershell..do you know about this function??– plasma33Jan 3, 2015 at 6:21
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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)– sonjzJan 6, 2015 at 1:03
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3 Answers
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
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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
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@chubbsondubs yup, i see the issue now, you always have to encode and decode in bytes, i'll update the answer– sonjzJun 27, 2018 at 1:11
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1Question was for "command line", both command prompt and PowerShell are command line shells for Windows. Command prompt being the archaic "stop using this" one.– sonjzMar 10, 2019 at 22:07
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This doesn't work in Powershell 6. In order for it to work, you must replace
-Encoding bytewith-AsByteStream– OmidMar 18, 2020 at 19:59
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.
answered Jan 3, 2015 at 3:33
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cygwin also has the 'head' command if you choose to use that option Jan 3, 2015 at 3:41
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@JeffClayton Shoot.. you're right, for some reason I was thinking cat instead of head Jan 3, 2015 at 3:43
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'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
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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.
Much faster than piped powershell commands, as in the selected answer; works at OS file system level.
Tested in Win 10
