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File Edition Utility

(Fun fact: Feu mean fire in French)

FEU is a sed-like utility making heavy use of regexs.


Each line is a command.

Commands are in this form:


A line can also be a keyword:

  • end End a block
  • loop Start an infinite loop
  • line Execute a block for each line of the input
  • print Print the input
  • do number Execute a block a specified number of times
  • func name Define a function
  • call name Call a function
  • __DATA__ The rest of the file is the input to the program
Mode Command format Description
/regex/flags Execute the next block for each strings matched by the regex
substitute s/regex/sub/flags Replace each occurence of a regex in the input
exit e/regex/flags Exit the current block if the input is matched by the regex (effect can be negated by adding the ! flag)
map m/regex1/sub1/regex2/sub2/.../regexN/subN/flags Same as s, but using a mapping
append a/text Append text at the end of the input (equivalent to s/$/text)
prepend p/text Prepend text at the start of the input (equivalent to s/^/text)
unary u/character Convert the input from decimal to unary using a specified character (the sign is ignored)
Unary U/character Convert the input from unary to decimal with a specified unary character
ignore i/text Comment
Shell S/command/arg1/arg2/.../argN Execute a shell command
Extended ecommand Execute an extended command

Extended commands:

Mode Command format Description
set s/var/regex/flags Set a variable to the portions of the input matched by the regex
push p/var Push the current input on the input stack and set the input to the specified variable
Pop p/var Set the variable to the current input and set the input to the value on the top of the input stack
undefine u/var Undefine a variable
append a/var Append the content of a variable at the end of the input
prepend p/var Prepend the content of a variable at the start of the input


See the examples folder