rev - reverse lines characterwise
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 then allocating the memory for the file may be unsuccessful.
For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.
The rev command is part of the util-linux package which can be downloaded from Linux Kernel Archive https://www.kernel.org/pub/linux/utils/util-linux/.