Skip to content

Latest commit

 

History

History
153 lines (105 loc) · 3.47 KB

003-the-cat-tac-command.md

File metadata and controls

153 lines (105 loc) · 3.47 KB
Raw

The cat command

The cat command allows us to create single or multiple files, to view the content of a file or to concatenate files and redirect the output to the terminal or files.

The "cat" stands for 'concatenate.' and it's one of the most frequently used commands in the Linux terminal.

Examples of uses:

  1. To display the content of a file in terminal:
cat <specified_file_name>
  1. To display the content of multiple files in terminal:
cat file1 file2 ...
  1. To create a file with the cat command:
cat > file_name
  1. To display all files in current directory with the same filetype:
cat *.<filetype>
  1. To display the content of all the files in current directory:
cat *
  1. To put the output of a given file into another file:
cat old_file_name > new_file_name
  1. Use cat command with more and less options:
cat filename | more
cat filename | less
  1. Append the contents of file1 to file2:
cat file1 >> file2
  1. To concatenate two files together in a new file:
cat file1_name file2_name merge_file_name
  1. Some implementations of cat, with option -n, it's possible to show line numbers:
cat -n file1_name file2_name > new_numbered_file_name

Syntax:

cat [OPTION] [FILE]...

Additional Flags and their Functionalities:

Short Flag Long Flag Description
-A --show-all equivalent to -vET
-b --number-nonblank number nonempty output lines, overrides -n
-e - equivalent to -vE
-T - Display tab separated lines in file opened with cat command.
-E - To show $ at the end of each file.
-E - Display file with line numbers.
-n --number number all output lines
-s --squeeze-blank suppress repeated empty output lines
-u - (ignored)
-v --show-nonprinting use ^ and M- notation, except for LFD and TAB
- --help display this help and exit
- --version output version information and exit

The tac command

tac is a Linux command that allows you to view files line-by-line, beginning from the last line. (tac doesn't reverse the contents of each individual line, only the order in which the lines are presented.) It is named by analogy with cat.

Examples of uses:

  1. To display the content of a file in terminal:
tac <specified_file_name>
  1. This option attaches the separator before instead of after.
tac -b concat_file_name tac_example_file_name
  1. This option will interpret the separator as a regular expression.
tac -r concat_file_name tac_example_file_name
  1. This option uses STRING as the separator instead of newline.
tac -s concat_file_name tac_example_file_name
  1. This option will display the help text and exit.
tac --help
  1. This option will give the version information and exit.
tac --version

Syntax:

tac [OPTION]... [FILE]...

Additional Flags and their Functionalities:

Short Flag Long Flag Description
-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