1-Minute Review Card: ls

Must Remember

• ls lists directory content.
• -l long format, -a all files, -A almost all.
• -t sort by time, -S sort by size, -r reverse.
• -h human readable size (for long format).
• . current directory, .. parent directory.

Option Style Rule

• - is for short option names: -l, -a, -t.
• -- is for long option names: --color=auto, --help.
• This is not about single vs many arguments.
• You can pass many of either style:
  • ls -la
  • ls --color=auto --time-style=iso

-l vs -n

• ls -l shows owner/group names (e.g., root, testuser).
• ls -n shows numeric owner/group IDs (UID/GID).

Time Sort Reminder

• ls -lt -> sort/display by mtime.
• ls -ltu -> sort/display by atime.
• ls -ltc -> sort/display by ctime.

Size Reminder

• -s shows allocated blocks column.
• -S sorts entries by size (largest first).
• Practical readable combo: ls -lSh.

Formatting Reminder

• ls -1 -> one entry per line.
• ls -m -> comma-separated list (same idea as --format=commas).
• ls -lQ -> quote file names.
• --time-style=locale|iso|full-iso changes date display in long listing.

8 Essential Commands

ls
ls -l
ls -a
ls -al
ls -lt
ls -lS
ls -lh
ls --help

Common Mistakes

• Mixing -s and -S (they are different).
• Forgetting hidden files when debugging (ls -a).
• Thinking UID means group (UID is user, GID is group).

Self-check (30 seconds)

1. How do I list parent directory?
2. How do I show one file per line with quotes?
3. How do I print long list with human-readable sizes?

Answers:

1. ls ..
2. ls -1Q
3. ls -lh