Info Catalog sed: Centering lines sed: Examples sed: Rename files to lower case

sed: Increment a number

 
 7.3 Increment a Number
 ======================
 
 This script is one of a few that demonstrate how to do arithmetic in
 'sed'.  This is indeed possible,(1) but must be done manually.
 
    To increment one number you just add 1 to last digit, replacing it by
 the following digit.  There is one exception: when the digit is a nine
 the previous digits must be also incremented until you don't have a
 nine.
 
    This solution by Bruno Haible is very clever and smart because it
 uses a single buffer; if you don't have this limitation, the algorithm
 used in ⇒Numbering lines cat -n, is faster.  It works by replacing
 trailing nines with an underscore, then using multiple 's' commands to
 increment the last digit, and then again substituting underscores with
 zeros.
 
      #!/usr/bin/sed -f
 
      /[^0-9]/ d
 
      # replace all trailing 9s by _ (any other character except digits, could
      # be used)
      :d
      s/9\(_*\)$/_\1/
      td
 
      # incr last digit only.  The first line adds a most-significant
      # digit of 1 if we have to add a digit.
 
      s/^\(_*\)$/1\1/; tn
      s/8\(_*\)$/9\1/; tn
      s/7\(_*\)$/8\1/; tn
      s/6\(_*\)$/7\1/; tn
      s/5\(_*\)$/6\1/; tn
      s/4\(_*\)$/5\1/; tn
      s/3\(_*\)$/4\1/; tn
      s/2\(_*\)$/3\1/; tn
      s/1\(_*\)$/2\1/; tn
      s/0\(_*\)$/1\1/; tn
 
      :n
      y/_/0/
 
    ---------- Footnotes ----------
 
    (1) 'sed' guru Greg Ubben wrote an implementation of the 'dc' RPN
 calculator!  It is distributed together with sed.
 

Info Catalog sed: Centering lines sed: Examples sed: Rename files to lower case