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I'm trying to test an embedded nand flash chip using the dd command (write random data to a file):

dd if=/dev/urandom of=/nand/storage/testnand/test.raw bs=100000 count=50 2> /dev/null

However, the unit I'm testing is running busybox v1, and it has been patched. The dd command is not recognized. Is there an alternative command that will help me achieve the same results?

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2 Answers 2

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head -c $((100000*50)) /dev/urandom > test.raw

will save 100000 * 50 = 5000000 bytes, combining Bash's Arithmetic expressions and head's -c number_of_bytes parameter.

For debugging: expanding on allquixotic's idea, this command prints "$i done" at 1000, 2000, etc.

{ for i in {1..100000}; do echo $i; if (( ($i % 1000) == 0 )); then echo "$i done" 1>&2; fi; done } > test.raw
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  • Ooh nice! :) Didn't think of generating data with head...
    – allquixotic
    May 3, 2013 at 18:19
  • @ignis - If I wanted this script to continue until there is an error or the user stops, would I need to add /dev/null back?
    – suffa
    May 3, 2013 at 18:30
  • @suffa The user can stop with Ctrl+C, and I believe the command will stop automatically if there's an error. 2>/dev/null merely hides the error messages, in no way it will influence the command itself.
    – ignis
    May 3, 2013 at 18:34
  • @ignis - keep getting a syntax error on the debugging section you added recently.
    – suffa
    May 3, 2013 at 19:18
  • @suffa I do not get errors, on Bash 4.2.37(1) / Ubuntu 12.10, Bash 4.2.45(2) / Arch Linux 2013.04, Bash 4.2.39(1) / Fedora 18. Does echo $0 return "bash"? If so, what version does bash --version print?
    – ignis
    May 3, 2013 at 19:39
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You can try

  • cat /dev/urandom > /nand/storage/testnand/test.raw
  • for i in $(seq 1 10000000); do echo $i >> /nand/storage/testnand/test.raw; done

I can't think of much else that would work if you don't even have dd or cat...

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  • Expanding on your idea, I'd do { for i in {1..100000}; do echo $i; done } > test.raw which opens test.raw only 1 time
    – ignis
    May 3, 2013 at 18:29
  • @ignis does the ellipsis in your comment account for: {1 seq 10000000}?
    – suffa
    May 3, 2013 at 18:34
  • @suffa Nope, it's an alternative syntax for seq 1 100000, documented here and here
    – ignis
    May 3, 2013 at 18:37

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