Linux tac command
Updated: 04/26/2017 by Computer Hope
About tac
Concatenate and print files in reverse.
Description
tac (which is "cat" backwards) concatenates each FILE to standard output just like the cat command, but in reverse: line-by-line, printing the last line first. This is useful (for instance) for examining a chronological log file in which the last line of the file contains the most recent information.
If no FILE is specified, or if the FILE is specified as "-", tac reverses the contents of standard input.
tac syntax
tac [OPTION] ... [FILE] ...
Options
| -b, --before | attach the line separator before each line of output instead of after. |
| -r, --regex | interpret the line separator as a regular expression (useful with the -s option, see below). |
| -s, --seperator=STRING | use STRING as the line separator instead of a newline. |
| --help | display command help and exit. |
| --version | output version information and exit. |
tac examples
tac file1.txt
Prints the lines of file1.txt in reverse, from last line to first.
Related commands
cat — Output the contents of a file.
tail — Print the last lines of a textfile.