atext: apply some operations to the input files (names from the stdin)

usage: atext [parameters]
parameters:
-ins {place} {text}: insert text, place can be 'begin','end' or a line number
  (negative numbers count backward from the end of the file).
  place can be defined with line contents, too:
  contains:{text}, equals:{text} - here the each line that fulfills the
  condition will be selected as insertion point

  text can select files, too: file:{filename} - here contents of the given file
  will be inserted

  several insertion can be specified at the same time, eacf of the will be
  applied to the input files

-a[fter]: the insertion will take place after the insertion position
  (default: before)
-rp {text1 text2}: replace each occurence of text1 with text2
-rpv {varname} {value}: replace the '$(varname)' texts with value
-rtv: replace vars with current time (YEAR, MON, DAY, HOUR, MIN, SEC)
-erp {search_expr} {val_expr}: if the search_expr evaluates to true, the
  current line is replaced by the value of val_expr (the runtime variable is
  'line').
-del {line}: delete the given line(s), exmaple: '10,20-25' or 'contains:foo'
or 'begin' or 'end'
-ed[el] {expr}: delete lines where the given expression evaluates to a nonzero
  value with the current line (the variable name is 'line').
-rm {text}: each occurence of the text will be removed
-fw: forward the names of the processed files to the output
-sp: forwarded file name separator is space (instead of newline)
any other parameter is treated as an input file
-rtws: remove trailing white spaces. The spaces and tabs will be removed from
  the end of the lines.
-rtabs {padder} {tabsize}: replace tabs with the padder and tab size. The
  tabs are interpreted so that they always align the text to the next tab-sized
  position.

Examples:
afind "*.txt" | atext -ins begin "Monty Python"
  -> the text will be inserted as the first line

afind "*.txt" | atext -ins end file:sign.txt
  -> the contents of sign.txt will be inserted at the end of the files

afind "*.txt" | atext -rp "Carl Palmer" "Cozy Powell"
  -> the text files will contain the 1985 ELP crew

afind "*.txt" | atext -rpv AUTHOR "Attila NAGY"
  -> each occurence of '$(AUTHOR)' will be replaced with the writer's name

afind "*.txt" | atext -rtv
  -> the '$(YEAR)', '$(MON)', '$(DAY)', '$(HOUR)', '$(MIN)', '$(SEC)'
     occurences will be replaced with the current time

afind "*.txt" | atext -del contains:Trotsky
  -> Stalin can (could have) remove(d) each reference to his opponent

afind "*.txt" | atext -ins contains:apple 'A fruit in the prev line' -a
  -> each line that contains the 'apple' text will be followed by the text

atext fruits.txt -erp "line []= 'apple'" "line + ' -> ' + str_upper(line)"
  -> the lines containing 'apple' will be trandformed to the concatenation of
     the original value, a horizontal arrow and the uppercase version of the
     line.

atext my_novel.txt -ed "line []= 'rem' || line []= '********'"
  -> delete lines from the file that contain a rem(ark) or a bunch of asterisks