rev

rev is a Python command line utility that aims to provide more string reversing functionality than the one that already exists.

Usage:

rev # Read strings line by line from standard input and reverse them

Reversing words:

rev -w # Reverse the word order

Blocks of texts are considered to be words if they are between whitespace or punctuation characters. These characters are called delimiters and can be edited with the flags --include-chars and --exclude-chars. Delimiter characters are kept in the same relative place to preserve sentence structure.

echo "I'm cool" | rev -w # using default delimiters
cool'm I
echo "I'm cool" | rev -w --exclude-chars "'"
cool I'm

If the goal is to reverse both the word order and have each word be reversed, you can specify the -c flag to also reverse the characters in each word

rev -w -c # Reverse the word order and the characters in each word

Input: rev takes a positional argument to denote the name of the file to read in from.

rev file.txt # Output the contents of the file with each line reversed

The flag --ignore-newlines ignores newlines and reverses the entire string.

rev file.txt --ignore-newlines # Reverse everything in the file, ignoring newlines

The full usage is as follows:

usage: rev.py [-h] [-o OUT] [-w [W]] [--ignore-lines]
              [--include-chars INCLUDE_CHARS] [--exclude-chars EXCLUDE_CHARS]
              [-c [C]] [-b [B]]
              [IN]

Reverse the input

positional arguments:
  IN                    The input file (standard in by default)

optional arguments:
  -h, --help            show this help message and exit
  -o OUT, --output OUT  The output file (standard out by default)
  -w [W], --word [W]    Reverse W words at a time. Leaves delimiters
                        (whitespace and punctuation by default) intact.
                        (default W is 1, meaning all words are reversed)
  --ignore-lines        Ignore newlines when reversing (so that using standard
                        input delays output when you enter EOF, nothing is
                        actually changed in the output)
  --include-chars INCLUDE_CHARS
                        Use the characters as delimiters to split on.
  --exclude-chars EXCLUDE_CHARS
                        Do not use the characters provided as delimiters.
  -c [C], --character [C]
                        Reverse C characters at time. If --word is specified,
                        reverse the characters in a word, and leave the word
                        order intact if W is 1. (default C is 1, meaning all
                        characters are reversed)
  -b [B], --byte [B]    Reverse B bytes of the input (default B is 1, meaning
                        all bytes are reversed)