# Reading Files: cat and less

cat prints a short file on the screen, less shows a long one a screen at a time with keys to move and search, and file tells you what kind of file something is before you open it.

Novice · Unix · Linux · Updated November 10, 2026

## After this lesson you can

- Read a short file with cat, and check what a file is with file first
- Page through and search a long file in less with Space, b, /, n and q

## Key takeaways

- cat and a file's name prints the whole file on the screen. It suits short files, such as a README or a settings file.
- less shows a long file one screen at a time. Space goes forward, b goes back, / searches, n finds the next match and q quits.
- file looks inside a file and says what kind it is, such as text, a picture or a program, whatever its name says.
- Reading never changes a file, so cat, less and file are safe to try on anything.

You download a small app, and its folder holds a README that says "read me first", a settings file, and a long list of what changed in each version. A file manager opens each one in whatever program it picks; on a web server there's no file manager at all, only a terminal. Either way the job is the same: see what's inside a file without changing it.

## Set up the practice folder

The examples use a made-up app folder, Recipe Box. Copy these lines into your terminal and press Enter. They make the folder and its three files, then list them. Module 2 teaches `printf`, and Module 5 the `for` loops; the lines are safe to run again for a fresh copy.

```bash
mkdir -p ~/terminal-practice/recipe-box && cd ~/terminal-practice/recipe-box
printf '# Recipe Box\n\nKeeps your family recipes in one place, with a shopping list.\n\nSettings:      settings.conf\nWhat changed:  CHANGELOG.md\n' > README.md
printf 'port=8080\ntheme=light\nlanguage=en\nshopping_list=on\n' > settings.conf
printf '# Recipe Box: what changed, newest first\n\n' > CHANGELOG.md
for v in $(seq 30 -1 13); do printf '## Version 1.%s\n- Small fixes and speed-ups\n\n' "$v" >> CHANGELOG.md; done
printf '## Version 1.12\n- New: dark mode, for cooking late at night\n\n' >> CHANGELOG.md
for v in $(seq 11 -1 1); do printf '## Version 1.%s\n- Small fixes and speed-ups\n\n' "$v" >> CHANGELOG.md; done
printf '## Version 1.0\n- The first version: add, find and print recipes\n' >> CHANGELOG.md
ls
```

```text
CHANGELOG.md  README.md  settings.conf
```

All three are **text files**: files of plain letters, numbers and punctuation that any program can read. Most READMEs, settings files and logs are text.

## cat: a short file, all at once

`cat` prints a file's text on the screen. Its name is short for *concatenate*, "join together", because it can print several files one after another. Give it the file's name:

```bash
cat README.md
```

```text
# Recipe Box

Keeps your family recipes in one place, with a shopping list.

Settings:      settings.conf
What changed:  CHANGELOG.md
```

The README points to the settings file, so read that next:

```bash
cat settings.conf
```

```text
port=8080
theme=light
language=en
shopping_list=on
```

That's what `cat` is for: files short enough to fit on your screen.

## less: a long file, one screen at a time

Now try `cat CHANGELOG.md`. Its 94 lines rush past, and only the last few stay on your screen. For a long file, use `less`, which shows one screenful and waits for you:

```bash
less CHANGELOG.md
```

```text
# Recipe Box: what changed, newest first

## Version 1.30
- Small fixes and speed-ups

## Version 1.29
- Small fixes and speed-ups

## Version 1.28
- Small fixes and speed-ups

## Version 1.27
- Small fixes and speed-ups

## Version 1.26
CHANGELOG.md
```

That's a window 16 lines tall; `less` fills yours. The last line shows the file's name at first, then a `:` (colon): `less` is waiting for a key. A program like this, which shows text a page at a time, is called a **pager**. These keys move you around:

- **Space** goes forward one screen, and **b** goes back one.
- The **up and down arrows** move one line at a time.
- **g** jumps to the top, and **G** (Shift+g) to the end, where the last line says `(END)`.
- **q** quits and gives you your prompt back. Nothing you do in `less` changes the file.

![A long paper scroll of CHANGELOG.md with a window frame over one part of it, labeled "the screen less shows you", an arrow down labeled "Space: the next screen" and an arrow up labeled "b: back one screen"](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/af2b0f509c7d4ca189b5398f42ba40fa.webp)

## Search inside less

To find a word in a long file, type `/` (read "slash"), then the word, and press Enter. As you type, the word shows on the bottom line. Find when dark mode arrived with `/dark`:

```text
- New: dark mode, for cooking late at night

## Version 1.11
- Small fixes and speed-ups

## Version 1.10
- Small fixes and speed-ups

## Version 1.9
- Small fixes and speed-ups

## Version 1.8
- Small fixes and speed-ups

## Version 1.7
:
```

The line with the match moves to the top of the screen. Press the up arrow once to see the line above it, `## Version 1.12`. When a word appears more than once, **n** jumps to the next match and **N** (Shift+n) back to the one before. Searches match capital letters exactly, so `/Dark` finds nothing here, and the bottom line says `Pattern not found  (press RETURN)`.

## file: what is it before you open it?

Not every file is text. A photo or a program is made of bytes that aren't letters, and `cat` on one fills the screen with strange symbols. (If that ever scrambles your terminal, type `reset` and press Enter.) `file` looks inside a file and tells you what it is:

```bash
file README.md settings.conf CHANGELOG.md
file /usr/bin/bash
```

```text
README.md:     ASCII text
settings.conf: ASCII text
CHANGELOG.md:  ASCII text
/usr/bin/bash: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=a292b52b679fb438b940f1c17e2e4951ac52ac89, for GNU/Linux 3.2.0, stripped
```

*ASCII text* means plain text: safe for `cat` and `less`. The long answer for `/usr/bin/bash` starts with *ELF … executable*: it's a program, so don't `cat` it. (On a Mac, programs show as *Mach-O*.) `file` goes by what's inside, not by the name, so a photo renamed `notes.txt` is still a picture to `file`.

## Try it in the terminal

[Terminal Quest: The Lighthouse, goal 3](https://www.ask-codey.com/games/terminal-quest/lighthouse/bash/step): played right on the lesson page.

You're the new lighthouse keeper, and Mara left you a note. Read the welcome note; type the first letters of its name and let Tab finish it.

## Check yourself

2 questions to try on the lesson page.

## So what

READMEs, settings, logs and notes are all text files. With `cat` for short ones, `less` for long ones and `file` when you're not sure, you can read any of them, on any computer, without changing a thing.

## Key terms

- [cat](https://www.ask-codey.com/glossary/cat)
- [less](https://www.ask-codey.com/glossary/less)
- [file](https://www.ask-codey.com/glossary/file-unix)
- [Text File](https://www.ask-codey.com/glossary/text-file)

## Cheat sheets

- [Reading Files: cat and less](https://www.ask-codey.com/cheat-sheets/bash-reading-files-cheat-sheet)

## Related

- [Looking Around: ls](https://www.ask-codey.com/lessons/bash-looking-around)
- [Getting Help](https://www.ask-codey.com/lessons/bash-getting-help)

Source: https://www.ask-codey.com/lessons/bash-reading-files