Viewing Files

Command Purpose Best For Key Features
cat Display entire file Small files - cat = concatenate
- Shows full content at once
- No scrolling
- Simple and fast
less View file with scrolling Large files - Scroll up/down
- Search (/word)
- Does not load whole file at once
- Exit with q
more View file page-by-page Medium files - Scroll forward only
- Limited backward navigation
- Older pager (less advanced than less)
head Show first few lines Quick preview - Default: shows first 10 lines
- Can set number: head -n 20 file
tail Show last few lines Logs / last lines - Default: last 10 lines
- Live updates with tail -f file

Structure: 

cat [OPTIONS] [FILE]
less [OPTIONS] FILE
more [OPTIONS] FILE
head [OPTIONS] [FILE]
tail [OPTIONS] [FILE]
head -n number_of_lines filename
tail -n number_of_lines filename

Examples: 

cat alphabet.txt          # Display entire file
less alphabet.txt         # View file with scrolling 
more alphabet.txt         # View file with scrolling, older/limited version
head alphabet.txt         # Show first 10 lines by default
tail alphabet.txt         # Show last 10 lines by default
head -n 5 alphabet.txt    # Show first 5 lines of the file
tail -n 5 alphabet.txt    # Show last 5 lines of the file

Command Line Pipes ( | )

  • | sends output of one command as input to another.
  • Helps filter and refine large outputs.
  • Commands run left → right; order matters.
  • Multiple pipes can be chained.

Examples:

ls /etc | head               # show first 10 entries
ls /etc/ssh | nl             # number all lines
ls /etc/ssh | nl | tail -5   # number first, then show last 5
ls /etc/ssh | tail -5 | nl   # take last 5, then number 1–5


ls /etc/ssh | nl
* ls /etc/ssh → show files * | → pass output * nl → number each line

Example:

1  ssh_config
2  ssh_config.d
3  sshd_config

Used to count files or reference them by number.