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File Viewing and Manipulation: cat, echo, less, head, tail, and clear
This guide provides an overview of common Linux commands to display, manipulate, and navigate file contents, as well as manage terminal output.
1. cat - Concatenate and Display File Contents
Description:
The cat command is used to display the contents of files, combine multiple files, or create new ones.
Syntax:
cat [options] [file...]
Common Options:
| Option | Description | Example |
|---|---|---|
-n |
Number all output lines | cat -n file.txt |
-b |
Number non-blank output lines | cat -b file.txt |
-s |
Suppress repeated empty lines | cat -s file.txt |
-A |
Show all characters, including non-printing ones | cat -A file.txt |
-T |
Display tabs as ^I |
cat -T file.txt |
-E |
Display a $ at the end of each line |
cat -E file.txt |
file1 file2 > combined |
Combine multiple files into one | cat file1.txt file2.txt > combined.txt |
Examples:
- Display the content of a file:
cat file.txt
- Combine multiple files into one:
cat file1.txt file2.txt > combined.txt
- Number lines in a file:
cat -n file.txt
2. echo - Print Text or Variables
Description:
The echo command outputs text or variables to the terminal or files.
Syntax:
echo [options] [string...]
Common Options:
| Option | Description | Example |
|---|---|---|
-e |
Enable interpretation of backslash escapes | echo -e "Line1\nLine2" |
-n |
Do not output the trailing newline | echo -n "No newline at the end" |
--help |
Display help and usage information | echo --help |
Common Backslash Escapes
| Escape Sequence | Description | Example |
|---|---|---|
\n |
New line | echo -e "Line1\nLine2" |
\t |
Horizontal tab | echo -e "Column1\tColumn2" |
\\ |
Backslash | echo -e "This is a backslash: \\" |
\" |
Double quote | echo -e "She said, \"Hello!\"" |
\a |
Alert (bell sound) | echo -e "\a" |
\b |
Backspace | echo -e "Text\b" |
Examples:
- Print a string:
echo "Hello, World!"
- Print a variable:
echo $HOME
- Write output to a file:
echo "This is a line" > file.txt
3. less - View File Contents Interactively
Description:
The less command allows you to scroll through file contents interactively.
Syntax:
less [options] [file]
Command-Line Options
| Option | Description | Example |
|---|---|---|
-N |
Show line numbers | less -N file.txt |
-S |
Do not wrap long lines (horizontal scrolling) | less -S file.txt |
-X |
Prevent clearing the screen upon exit | less -X file.txt |
-G |
Disable search result highlighting | less -G file.txt |
-i |
Ignore case in search unless uppercase is used | less -i file.txt |
-p pattern |
Start at the first occurrence of a pattern | less -p "search_term" file.txt |
-? or --help |
Display help and options | less --help |
Keybindings (Interactive Navigation)
| Key | Action |
|---|---|
Up / Down |
Scroll up/down one line |
PageUp / PageDown |
Scroll up/down one page |
Space |
Scroll forward one page |
b |
Scroll back one page |
G |
Jump to the end of the file |
g |
Jump to the beginning of the file |
/pattern |
Search forward for a pattern |
?pattern |
Search backward for a pattern |
n |
Repeat the last search (forward) |
N |
Repeat the last search (backward) |
h |
Display help screen |
q |
Quit less |
Example:
- View a file:
less file.txt
4. head - Display the Beginning of a File
Description:
The head command shows the first few lines of a file (default is 10).
Syntax:
head [options] [file]
Common Options:
| Option | Description | Example |
|---|---|---|
-n N |
Display the first N lines of the file | head -n 5 file.txt |
-c N |
Display the first N bytes of the file | head -c 20 file.txt |
-q |
Suppress file name headers when multiple files are used | head -q file1.txt file2.txt |
-v |
Always show file name headers | head -v file.txt |
file |
Specify the file to read from | head file.txt |
Examples:
- Display the first 10 lines:
head file.txt
- Display the first 5 lines:
head -n 5 file.txt
5. tail - Display the End of a File
Description:
The tail command shows the last few lines of a file (default is 10). It can also be used to monitor file changes in real time.
Syntax:
tail [options] [file]
Common Options:
| Option | Description | Example |
|---|---|---|
-n N |
Display the last N lines of the file | tail -n 10 file.txt |
-c N |
Display the last N bytes of the file | tail -c 50 file.txt |
-f |
Follow the file as it grows (useful for log files) | tail -f logfile.log |
-q |
Suppress file name headers when multiple files are used | tail -q file1.txt file2.txt |
-v |
Always show file name headers | tail -v file.txt |
-F |
Similar to -f, but it will attempt to reopen the file if it is rotated |
tail -F logfile.log |
Examples:
- Display the last 10 lines:
tail file.txt
- Display the last 20 lines:
tail -n 20 file.txt
- Monitor a log file in real time:
tail -f logfile.log
6. clear - Clear Terminal Screen
Description:
The clear command clears all output from the terminal screen.
Syntax:
clear
Example:
- Clear the screen:
clear
Cheatsheet: File Viewing and Manipulation
| Command | Description | Example |
|---|---|---|
cat file |
Display the contents of a file | cat file.txt |
cat file1 file2 > combined |
Combine files into one | cat file1.txt file2.txt > out.txt |
echo "text" |
Print text or variables | echo "Hello, World!" |
less file |
View file contents interactively | less file.txt |
head file |
Display the first 10 lines of a file | head file.txt |
head -n 5 file |
Display the first 5 lines of a file | head -n 5 file.txt |
tail file |
Display the last 10 lines of a file | tail file.txt |
tail -n 20 file |
Display the last 20 lines of a file | tail -n 20 file.txt |
tail -f file |
Monitor a file for changes in real time | tail -f logfile.log |
clear |
Clear the terminal screen | clear |