First, Introduction
1. The cat command outputs files or standard input combinations to standard output, which is commonly used to view the contents of a file. Syntax cat [options] [parameters]
2. The TAC command inverts each specified file by line and writes to standard output. If you do not specify a file, or if the file is "-", the data is read from the standard input, i.e. the first line is displayed at the end and the last line is displayed first. Grammar tac [Options] [parameters]
Second, common options
1. Common options for CAT commands
-A: Equals-vet
-E: Equals-ve
-E: Show "$" at the end of each line
-T: equivalent to-VT
-T: Show the jump character as ^i
-V: Use ^ and M-references, except LFD and TAB
-N: Numbering all lines of the output
-B: Number of non-null output lines
-S: Do not output multiple lines of blank lines
--help: Displays this help message and exits
2. Common options for TAC commands
-B: Add separator flags before line ends
-R: The separation flag is treated as a regular expression to parse
-S string: Use the specified string instead of line break as the delimited flag
--help: Displays this help message and exits
Linux common commands brief--cat and TAC
