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REV(1) FreeBSD General Commands Manual REV(1)
NAME
rev - reverse lines of a file
SYNOPSIS
rev [file ...]
DESCRIPTION
The rev utility copies the specified files to the standard output,
reversing the order of characters in every line. If no files are
specified, the standard input is read.
EXAMPLES
Reverse the text from stdin:
$ echo -e "reverse \t these\ntwo lines" | rev
eseht esrever
senil owt
FreeBSD 14.0-RELEASE-p6 June 27, 2020 FreeBSD 14.0-RELEASE-p6