rev

Reverse the text string "hello"

$ echo "hello" | rev

Reverse an entire file and print to stdout

$ rev [file]

rev [option] [file...]

The rev utility copies the specified files to standard output, reversing the order of characters in every line. If no files are specified, standard input is read.

This utility is a line-oriented tool and it uses in-memory allocated buffer for a whole wide-char line. If the input file is huge and without line breaks than allocate the memory for the file may be unsuccessful.

-V, --version

Display version information and exit.

-h, --help

Display help text and exit.

The rev command is part of the util-linux package and is available from Linux Kernel Archive.

tac(1)