Shell Utilities

Problem

  1. You want to compare 2 streams, with byte offset and line numbers?
  2. Pull off content with a byte offset?
  3. Display lines before or after a pattern?
  4. Send an email – upon job failure?


Solution

The shell is a powerful beast! Anything is possible … with a little know-how. 🙂 See the examples.



Example


  1. md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
    # cmp good for comparing output with file contents, or diffing files. Outputs byte offset and line number. md5sum creates a hash (checksum) of file.
  2. dd bs=1 skip=106 if=infile
    # disk to disk copy, example outputs infile with offset of 106 bytes (block size of 1 byte, skip 106 bytes).
  3. Ever needed to display a line before or after a pattern. Yep sure you can use Perl, but this is a bit simplier to work out.

    See the code here

    See a run through screen shot here

    Usage – ppgrep #1 #2 pattern file – where #1 is the number of lines prior to the pattern (could be 0) and #2 is number of lines post pattern.

  4. Sending email upon UNIX cron failure




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