Bash Tac Command

tac command in Linux is used to concatenate and print files in reverse. This command will write each FILE to standard output, the last line first. When no file is specified then this command will read the standard input. Example: It will print files in reverse.

1. What is TAC in bash?
2. What is $? In Shell?
3. How install TAC Linux?
4. What is the difference between CAT and TAC?
5. How do you clear the cat command in Linux?
6. What is the use of cat command in Unix?
7. What is $1 script Linux?
8. Why is it called shebang?
9. How do I run a shell script command?
10. What is Linux NL command?
11. What does touch command do in Linux?
12. What is less and more command in Linux?

What is TAC in bash?

Also known as reverse cat, tac a simple command-line utility that lets you reverse lines in output using the | builtin pipe operator and tac. ... That is, if you have a command, left-hand side (lhs), and want to reverse the contents of its output, all you would do is type lhs | tac. That's it!

What is $? In Shell?

$? is a special variable in shell that reads the exit status of the last command executed. After a function returns, $? gives the exit status of the last command executed in the function.

How install TAC Linux?

4 Answers

1. Install Homebrew.
2. brew install coreutils.
3. ln -s /usr/local/bin/gtac /usr/local/bin/tac apparently not needed with latest Homebrew, see comment by Ran Ever-Hadani below.

What is the difference between CAT and TAC?

Tac is practically the reverse version of cat command (also spelled backwards) which prints each line of a file starting from the bottom line and finishing on the top line to your machine standard output.

How do you clear the cat command in Linux?

5 Ways to Empty or Delete a Large File Content in Linux

1. Empty File Content by Redirecting to Null. ...
2. Empty File Using 'true' Command Redirection. ...
3. Empty File Using cat/cp/dd utilities with /dev/null. ...
4. Empty File Using echo Command. ...
5. Empty File Using truncate Command.

What is the use of cat command in Unix?

The cat (short for “concatenate“) command is one of the most frequently used command in Linux/Unix like operating systems. cat command allows us to create single or multiple files, view contain of file, concatenate files and redirect output in terminal or files.

What is $1 script Linux?

$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. ... $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)

Why is it called shebang?

In French, chabane means "hut" and it has been speculated that shebang is a corruption of the word, which could have been familiar to Civil War soldiers from Louisiana. ... Whatever the case, shebang took on an additional meaning leading to the familiar phrase "the whole shebang."

How do I run a shell script command?

Steps to write and execute a script

1. Open the terminal. Go to the directory where you want to create your script.
2. Create a file with . sh extension.
3. Write the script in the file using an editor.
4. Make the script executable with command chmod +x <fileName>.
5. Run the script using ./<fileName>.

What is Linux NL command?

nl command is a Unix/Linux utility that is used for numbering lines, accepting input either from a file or from STDIN. It copies each specified file to STDOUT, with line numbers appended before the lines.

What does touch command do in Linux?

The touch command is a standard command used in UNIX/Linux operating system which is used to create, change and modify timestamps of a file.

What is less and more command in Linux?

Learn Linux 'less' Command

Similar to more, less command allows you to view the contents of a file and navigate through file. The main difference between more and less is that less command is faster because it does not load the entire file at once and allows navigation though file using page up/down keys.