---
name: "uu-join"
section: "1"
platform: "linux"
package: "uutils-coreutils"
version: "0.12.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/uu-join"
---

# uu-join(1)

For each pair of input lines with identical join fields, write a line to standard output. The default join field is the first, delimited by blanks. When FILE1 or FILE2 (not both) is -, read standard input.

## NAME

join - For each pair of input lines with identical join fields, write a line to standard output. The default join field is the first, delimited by blanks.

When FILE1 or FILE2 (not both) is -, read standard input.

## SYNOPSIS

**join** \[OPTION\]... FILE1 FILE2

## DESCRIPTION

For each pair of input lines with identical join fields, write a line to standard output. The default join field is the first, delimited by blanks.

When FILE1 or FILE2 (not both) is -, read standard input.

## OPTIONS

- **-a** *\<FILENUM\>*

  also print unpairable lines from file FILENUM, where FILENUM is 1 or 2, corresponding to FILE1 or FILE2

  *Possible values:*

  - •

    1

  - •

    2

- **-v** *\<FILENUM\>*

  like -a FILENUM, but suppress joined output lines

  *Possible values:*

  - •

    1

  - •

    2

- **-e** *\<EMPTY\>*

  replace missing input fields with EMPTY

- **-i**, **--ignore-case**

  ignore differences in case when comparing fields

- **-j** *\<FIELD\>*

  equivalent to '-1 FIELD -2 FIELD'

- **-o** *\<FORMAT\>*

  obey FORMAT while constructing output line

- **-t** *\<CHAR\>*

  use CHAR as input and output field separator

- **-1** *\<FIELD\>*

  join on this FIELD of file 1

- **-2** *\<FIELD\>*

  join on this FIELD of file 2

- **--check-order**

  check that the input is correctly sorted, even if all input lines are pairable

- **--nocheck-order**

  do not check that the input is correctly sorted

- **--header**

  treat the first line in each file as field headers, print them without trying to pair them

- **-z**, **--zero-terminated**

  line delimiter is NUL, not newline

- **-h**, **--help**

  Print help

- **-V**, **--version**

  Print version

## VERSION

v(uutils coreutils) 0.12.0