# cat

_Peios / Using Peios / Peiosutils / Viewing and joining text_

> Print files to standard output, and concatenate several files into one stream.

`cat` prints the contents of files. Its name is short for "concatenate" — given several files, it prints them one after another, as a single stream.

```
cat [options] [file...]
```

```
$ cat notes.txt
$ cat part1.txt part2.txt part3.txt > whole.txt
```

With no file — or with the name `-` — `cat` reads standard input, which is what makes it useful in a pipeline or for capturing typed input into a file.

## Plain use

Most of the time `cat` is run with no options at all: it copies its input to its output, byte for byte, unchanged. The options exist for the times you want to *see* something about the text that is normally invisible, or to adjust spacing and numbering.

## Numbering lines

| Option | Effect |
|---|---|
| `-n`, `--number` | Number every output line. |
| `-b`, `--number-nonblank` | Number only the non-empty lines. Overrides `-n`. |

## Making invisible characters visible

These options reveal characters that normally print as nothing, or as whitespace — useful when a file is not behaving and you suspect a stray tab or control character.

| Option | Effect |
|---|---|
| `-E`, `--show-ends` | Print a `$` at the end of each line, so trailing spaces become visible. |
| `-T`, `--show-tabs` | Print tab characters as `^I` instead of as whitespace. |
| `-v`, `--show-nonprinting` | Print control and other non-printing characters using `^` and `M-` notation (leaving newline and tab as they are). |
| `-e` | Shorthand for `-vE`. |
| `-t` | Shorthand for `-vT`. |
| `-A`, `--show-all` | Shorthand for `-vET` — show ends, tabs, and all non-printing characters at once. |

## Adjusting spacing

| Option | Effect |
|---|---|
| `-s`, `--squeeze-blank` | Collapse runs of blank lines into a single blank line. |

## Exit status

| Code | Meaning |
|---|---|
| `0` | Every file was printed. |
| `1` | A file could not be read. |

Related content:

- [tac](/peios/using-peios/peiosutils/viewing-and-joining-text/tac.md)
- [more](/peios/using-peios/peiosutils/viewing-and-joining-text/more.md)
- [Viewing and joining text](/peios/using-peios/peiosutils/viewing-and-joining-text/overview.md)