How do you read and display file contents from the command line?

Question

Accepted Answer

cat dumps the whole file, head/tail show the first/last lines, and less pages through big files one screen at a time.
Pick the tool by file size and intent: cat is fine for short files but floods your terminal with a large one. head/tail peek at the ends (great for log files — tail -f even follows new lines live as they're written). less is the safe default for anything big because it doesn't load the whole file into memory — it streams pages on demand, with search (/) and scrolling built in.
Common file viewing commands:

Command
Purpose

cat file
Display entire file

head file
First 10 lines

head -n 5 file
First 5 lines

tail file
Last 10 lines

tail -n 20 file
Last 20 lines

tail -f file
Follow file updates

less file
Paginated viewer

more file
Simple pager

Combining with pipes:
# First 10 users from passwd:
head -n 10 /etc/passwd

# Last 2 users:
cat /etc/passwd | tail -n 2

# Follow log in real-time:
tail -f /var/log/syslog

Less navigation:

Space = next page
b = previous page
/pattern = search
q = quit

Tip: Use less for large files - it doesn't load the entire file into memory!

Command	Purpose
`cat file`	Display entire file
`head file`	First 10 lines
`head -n 5 file`	First 5 lines
`tail file`	Last 10 lines
`tail -n 20 file`	Last 20 lines
`tail -f file`	Follow file updates
`less file`	Paginated viewer
`more file`	Simple pager