#Bash 的 tac 命令
tac [OPTION]... [FILE]...
功能
将文件的内容顺序逆转，拼接多个文件并打印到标准输出。
文件内顺序逆转，文件之间顺序不变。
类型
可执行文件（/usr/bin/tac），属于 coreutils。
参数
OPTION选项：-b,--before- 将分隔符放在前面而不是后面-r,--regex- 将分隔符当作正则表达式解析-s,--separator=STRING- 使用STRING作为分隔符；默认为换行符（\n）--help- 显示帮助--version- 显示版本
FILE- 文件列表；如果没有这个参数或指定为-，则读取标准输入
#示例
$ cat 1.txt 2.txt # 正序查看文件内容
1
2
3
A
B
C
$ tac 1.txt 2.txt # 逆序查看文件内容
3
2
1
C
B
A
#相关命令
| 命令 | 说明 |
|---|---|
| cat | 正序拼接文件内容并打印到标准输出 |
#推荐阅读
#手册
TAC(1) User Commands TAC(1) NAME tac - concatenate and print files in reverse SYNOPSIS tac [OPTION]... [FILE]... DESCRIPTION Write each FILE to standard output, last line first. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -b, --before attach the separator before instead of after -r, --regex interpret the separator as a regular expression -s, --separator=STRING use STRING as the separator instead of newline --help display this help and exit --version output version information and exit AUTHOR Written by Jay Lepreau and David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO cat(1), rev(1) Full documentation <https://www.gnu.org/software/coreutils/tac> or available locally via: info '(coreutils) tac invocation' GNU coreutils 9.4 April 2024 TAC(1)